cim manual

U.V.Patel College of Engineering

MECHANICAL & MECHATRONICS ENGINEERING DEPARTMENT

Laboratory manual

M.tech.cad-cam (semester-I)

Computer integrated manufacturing (3 ME 1 1 5 )

U.V.Patel College Of Engineering GANPAT UNIVERSITY Ganpat Vidyanagar,

Mehsana-Gozaria HighwayMehsana - 382711, INDIA

U.V.Patel College of Engineering

Mehsana-Gozaria Highway Mehsana - 382711, INDIA

Certificate

This is certify that

Mr. / Ms.___________________________________ Roll no.____________of

______semester of M.tech.Cad-Cam has satisfactorily completed his/her work

in computer integrated manufacturing during the

year____________to_____________within four walls of U.V.patel College of

engineering.

Date of submission _______________________

Staff in charge _______________________

Head of Mech. Engg.Department __________________

INDEX

Sr.

No

Name of Experiment Date Page No. Sign.

1

TO STUDY INTRODUCTION TO COMPUTER

INTEGRATED MANUFACTURING.

2

TO STUDY INTRODUCTION TO FMS,

FLEXIBILITIES IN FMS AND ITS

MENASUREMENT CRITERION.

3

TO STUDY QUANTITATIVE ANALYSIS OF FMS

USING BOTTLENECK MODEL.

4

TO STUDY GROUP TECHNOLOGY AND

STRUCTURE OF CODING SYSTEM.

5

ANALYSIS OF MATERIAL HANDLING AND

STORAGE SYSTEM

6

TO STUDY ABOUT NC, CNC, DNC AND VNC

MACHINE TOOLS ALONG WITH ITS

SPECIFICATION AND MODERN FEATURES

7

MANUAL PART-PROGRAMMING FOR CNC

TURNING CENTER AND MACHINING CENTER.

8

STUDY OF CAD CAM INTEGRATION.

9

TO STUDY INTRODUCTION OF NETWORKING

AND COMMUNICATIONS.

10 CASE STUDY OF CIM

Computer Integrated Manufacturing

1

AIM: TO STUDY INTRODUCTION TO COMPUTER INTEGRATED

MANUFACTURING.

CIM DEFINATION:

Computer Integrated Manufacturing, known as CIM, is the phrase used to describe

the complete automation of a manufacturing plant, with all processes functioning under

computer control and digital information tying them together.

Computer-integrated manufacturing (CIM) may be viewed as the successor

technology which links computer-aided design (CAD), computer-aided manufacturing

(CAM), robotics, numerically controlled machine tools (NCMT), automatic storage and

retrieval systems (AS/RS), flexible manufacturing systems (FMS), and other computer-based

manufacturing technology.

Computer-integrated manufacturing is also known as integrated computer-aided

manufacturing (ICAM). Auto factoring includes computer-integrated manufacturing, but also

includes conventional machinery, human operators, and their relationships within a total

system.

EVOLUTION OF CIM:

Manufacturing industries have evolved tremendously from cottage industries in the

early 16th century to the global force as it stands today. The characteristics of the present

world market include higher competition, shorter product life cycles. Greater product

diversity, fragmented markets, variety and complexity and smaller hatch sizes to satisfy a

variety of customer profiles .

Furthermore, non-price factors, such as quality, product design, innovation and

delivery services are the primary determinants of product success in today's global arena . To

achieve these requirements, manufacturing companies need to be flexible. adaptable.

GANPAT UNIVERSITY

DEPARTMENT OF MECHANICAL AND MECHATRONICS ENGINEERING

U V PATEL COLLEGE OF ENGINEERING

COMPUTER INTEGRATED MANUFACTURING ( 3 ME1 1 5 )

M. TECH CAD- CAM.

EXPERIMENT NO: 1

..../..../........

DATE: ..../..../........


2

responsive to changes, proactive and be able to produce variety of products in a short time at

a lower cost in addition, they should be able to address new environmental requirements,

complex social issues and concerns. Hence, manufacturing companies are compelled to seek

advanced technologies as a panacea for all these needs.

The most significant outcome of this search resulted in the concept of computer

integrated manufacturing (ClM) in the early 1970s.

The concept of ClM was initially coined by Dr. Joseph Harrington in 1973 in the

book "Computer Integrated manufacturing".

However, until the early 1980s, CIM did not become a commonly known acronym as

it exists today.

The idea of "Digital Manufacturing is a vision for the 1980s. In the 1980s, Computer

Integrated Manufacturing was developed and promoted by machine tool manufacturers and

the CASA/SME (Computer and Automated Systems Association /Society for Manufacturing

Engineers).

CIM HARDWARE:

CIM hardware includes all the devices which are having physical presence. All the

devices which we can see, touch, can operate with application of human effort is known as a

hardware, in case of CIM all the applications accept programs are hardware. Majorly we can

classify them in this m/c tool format.

CIM Hardware


3

Manufacturing equipment such as machines or computerized work centers, Robotic

work cells, DNC/FMS systems, VNC systems, Work handling &tool handling devices,

Inspection machines etc…

Computers ,controllers ,CAD/CAM systems ,work stations/terminals, Data entry

terminals, Bar code readers, Printers ,plotters and other peripheral devices,

modems ,cables ,connectors etc….

CIM SOFTWARE:

CIM software is combination of following function software:

MIS (management information system):

MIS software helps for managing your accounts, inventory, taxation, payroll, stock,

banking, financial and other records. MIS involves all aspects of gathering, storing, tracking,

retrieving and using information within a business or organization. All the policies,

procedures, and practices that direct an organization's operations and the staff that interact

with the information, combined with the software and hardware, comprise an information

system.

PLANNING AND SCHEDULING:

It delivers a single database that contains all data for the software modules, which would

include:

Manufacturing:

Engineering, bills of material, scheduling, capacity, workflow management, quality

control, cost management, manufacturing process, manufacturing projects,

manufacturing flow

Supply chain management:

Order to cash, inventory, order entry, purchasing, product configuration, supply

chain planning, supplier scheduling, inspection of goods, claim processing,

commission calculation

Financials:

General ledger, cash management, accounts payable, accounts receivable, fixed assets

Project management:

Costing, billing, time and expense, performance units, activity management

Human resources :


4

Human resources, payroll, training, time and attendance, roistering, benefits

Customer relationship management:

Sales and marketing, commissions, service, customer contact and call center support.

Data warehouse and various self-service interfaces for customers, suppliers, and employees

Access control - user privilege as per authority levels for process execution

Customization - to meet the extension, addition, change in process flow.

COMPUTER AIDED DESIGN: (CAD)

Computer-aided design software is the use of computer technology for the design of

objects, real or virtual. The design of geometric models for object shapes. Phesibility of

design, testing as per software programs based on practical observations. Static, kinetic and

dynamic analysis of design.

COMMUNICATION:

Communication software is used to provide remote access to systems and exchange

files and real-time messages in text, audio and/or video formats between different

computers. This includes terminal emulators, file transfer programs, chat and instant

messaging programs, as well as similar functionality integrated within MUDs(multi-user

dungeon).This is for creating proper communication between person to person, person to

machine, machine to machine, machine to person..

OFFICE AUTOMATION:

Office Automation software is very beneficial to the company having big kind of

business for export and import. This Office Automation software is the easier way to store

details of the multiple company (you own) or working with. The Office Automation software

can be used any time and you can store as many data as you want to. Office Automation

software will keep record of all the things that is entered by you.

MAJOR AREAS OF CIM:

Areas Of CIM includes major four areas which are having their own parts which we

can include with them:


5

PRODUCTION MANAGEMENT SYSTEM:

Management information system, Sales Marketing, Finance, Database

management, Communication, Network management.

DESIGN AND MANUFACTURING SUPPORT SYSTEM:

Modeling and Design, Simulation, Analysis, Manufacturing area control

Process Planning, Manufacturing facilities, Quality management.

MACHINE TOOLS:

Work flow automation, driving devices

MATERIAL HANDLING SYSTEM:

Ordeal entry, Job ticketing, Material storage units, etc….

ELEMENTS OF CIM:

We can say that there are basically nine major elements of CIM system:

Marketing: The need for a product is defined by the marketing division. The

specifications of the product, the projection of manufacturing quantities and the

strategy for marketing the product are also decided by the marketing dept.

Product Design: The design department of the company establishes the initial

database for the production of a proposed product. In CIM system this is

accomplished through activities such as geometric modeling and computer aided

design while considering the product requirement and concept generated by the

creativity of the design engineer.


6

Planning: The planning department takes the database established by the product

design and enriches it with production data and information to produce a plan for

the production of product.

Purchase: The purchase department is responsible for placing the purchase orders

and follows up, receives the item, arrange for inspection and supply the items to

store for eventual supply to manufacture and assembly.

Manufacturing Engineering: Manufacturing Engineering is activity of carrying out

the production of the product, involving further enrichment of the database with

performance data and information about the production equipment and processes.

Factory Automation Hardware: Factory automation equipment further enriches

the database with equipment and process data, resident either in the operator or the

equipment to carry out the production process.

Warehousing: Ware housing is the function involving storage and retrieval of raw

material, components, finished goods as well as shipment items.

Finance: Finance deals with the resource pertaining to money. Planning of

investment ,working capital, cash flow control, accounting, and allocation of funds

are the major task of finance department.

Information Management: It is perhaps one of the crucial tasks in CIM.This

involves master production schedule, database management, communication,

manufacturing system integration and management information systems.

Which can be directly understand by figure


7

ACTIVITIES OF CIM:

CIM Technology ties together all the manufacturing related functions in a company:

Activities of CIM

Cad,Shopdata,FEM,MEM,Analysis,Drafting,Processplanning,ToolDesign,Scheduling

,Si-mulation,CNC,Robots,FMS,AS/RS,QC.

Marketing, Finance, Purchase, Human Resource, ERP, Shipping, Database.


8

Machine Tool ,Material Handling system ,Computer system ,FEM ,Element

Modeling ,MEM,ERP(Enterprise Resource Planning) ,QC.

KEY CHALLENGES:

There are three major challenges to development of a smoothly operating Computer

Integrated Manufacturing system:

Integration of components from different suppliers:

When different machines, such as CNC, conveyors and robots, are using different

communications protocols. In the case of AGVs, even differing lengths of time for

charging the batteries may cause problems.

Data integrity:

Data integrity is a term used in computer science and telecommunications that can

mean ensuring data is "whole" or complete the condition in which data are identically

maintained during any operation, the preservation of data for their intended use, or,

relative to specified operations, and the prior expectation of data quality.

: The higher the degree of automation, the more critical is the integrity of the data

used to control the machines. While the CIM system saves on labor of operating the

machines, it requires extra human labor in ensuring that there are proper safeguards

for the data signals that are used to control the machines.

Process control:

Process control is a statistics and engineering discipline that deals with architectures,

Mechanism s, and algorithms for controlling the output of a specific process....

Computers may be used to assist the human operators of the manufacturing facility,

but there must always be a competent engineer on hand to handle circumstances

which could not be foreseen by the designers of the control software.


9

Set up time, Quality, Manufacturing, Inventory, Flexibility, and Distance.

Manufacturing industry Goals.

Market position, Global economy, etc…

CIM WHEELS:

CASA/SME (Computer and automated system association of society of

manufacturing Engineers) has suggested a framework, the CIM WHEEL to explain the

meaning of CIM.

CIM is a closed loop system whose prime inputs are product requiring concept prime

output are finished product.

CIM WHEEL depicts a central core (Integrated System Architecture) That handles

the common manufacturing data and is concern with information resources management

and communication.

The radial sectors surrounding the core represent the various activities of

manufacturing processing design, material, processing and inspection.

This activity has been grouped under three categories.

Manufacturing planning and control,

Product process,

Factory Automation

The outer rim represents the upper management functions, grouped into four

categories:

Strategic Planning

Marketing

Manufacturing and

HRManagement

The modifications have been done by researchers for making the CIM WHEEL

acceptable in all industries as per requirements.

Key Strengths:

• CIM creates a database of information.


10

• CIM Can be applied to other sectors.

• CIM is low cost, low effort to get started.

• Manufacturing Planning and Scheduling is possible.

• Easy to understand islands of the CIM.

• Resource allocation is easier than conventional method.

Key Weaknesses:

• No compelling reason for growers to participate.

• Needs on-the-ground (arms-&-legs) facilitation.

• It cannot show complete connection between different island of CIM.

• No clear instructions are there for implementation.

• It do not have time constrain so may take months for implementation.

Declared by CASA/SME in 1980, 1985, 1986.

CASA/SME 1980.

Figure:-Wheel-CASA/SME 1980


11

CASA/SME 1986

CASA SME/1985(CIM ENTERPRISE WHEEL)

Figure:-CIM Wheel-CASA SME 1986

Figure- CIM ENTRPRISE WHEEL


12

Six Perspectives on the New Manufacturing Enterprise:

The new Manufacturing Enterprise Wheel describes six fundamental elements for

competitive manufacturing:

1. The central role of the customer and evolving customer needs. A clear

understanding of the marketplace and customer desires is the key to success.

Marketing, design, manufacturing, and support must be aligned to meet customer

needs. This is the bull's-eye, the hub of the Wheel, the vision and mission of the

enterprise.

2. The role of people and teamwork in the organization. Included here are the

means of organizing, hiring, training, motivating, measuring, and communicating to

ensure teamwork and cooperation. This side of the enterprise is captured in ideas

such as self-directed teams, teams of teams, the learning organization, leadership,

metrics, rewards, quality circles, and corporate culture.

3. The revolutionary impact of shared knowledge and systems to support people

and processes. Included here are both manual and computer tools to aid research,

analysis, innovation, documentation, decision-making, and control of every process

in the enterprise.

4. Key processes from product definition through manufacturing and customer

support. There are three main categories of processes: product/process definition;

manufacturing; and customer support. Within these categories 15 key processes

complete the product life cycle.

5. Enterprise resources (inputs) and responsibilities (outputs). Resources include

capital, people, materials, management, information, technology, and suppliers.

Reciprocal responsibilities include employee, investor, and community relations, as

well as regulatory, ethical, and environmental obligations. In the new manufacturing

enterprise, administrative functions are a thin layer around the periphery. They bring

new resources into the enterprise and sustain key processes.

6. The manufacturing infrastructure. While a company may see itself as self-

contained, its success depends on customers, competitors, suppliers, and other

factors in the environment. The manufacturing infrastructure includes: customers

and their needs, suppliers, competitors, prospective workers, distributors, natural


13

resources, financial markets, communities, governments, and educational and

research institutions.

1) Customer

In the end, every activity in the manufacturing enterprise should contribute

something of value to the customer. Providing superior value to the customer generates

growth and profits.

The role of an enterprise mission and vision is to align all work toward meeting--and

surpassing--customer expectations. This is the bull's-eye, the hub, and the center of the

new Manufacturing Enterprise Wheel.

A customer-centered mission provides a clear direction to align

activities and empowers the work of teams in the new manufacturing

enterprise.

Recent years have seen unprecedented experimentation in the

organization of manufacturing enterprises. Start-up companies grew

and became giants. Huge conglomerates formed from other

companies. Giant companies faltered, with some regaining their competitive edge.

Others are gone. The globalization of manufacturing continued at a dizzying pace, from

small niche producers to the largest international firms.

These successes--and failures--have proven the need for a clear mission and vision,

focused on the customer needs. Profits and growth can only be sustained when customer

needs are met or exceeded.

2) People and Teamwork in the Organization (P-T-O)

All members of the organization stake their futures on their ability to deliver value to the

customer, and earn profits in return. The central role of people in the organization forms

the inner circle of the Wheel.

The enterprise is only as strong as its people, organization, and culture.

Today's highly competitive worldwide markets require a new approach to managing,

organizing, and applying the knowledge and skills of people. When venture capitalists

consider funding a new company, their first consideration are people their knowledge,

their experience, their motivation. When successful companies explain their success, the

answer is much the same: it is "our people and our organization." When Japanese or

German business leaders explain the manufacturing success of their nations, with fewer


14

natural resources than many, they again point to people. Manufacturing success builds on

the education, skills, drive, cooperation, and leadership of people.

3) Shared Knowledge and Systems:

In the past, epochs were named by the dominant materials and tools of the age: the

Stone Age, the Bronze Age, the Iron Age. Materials and processes are still evolving. Yet,

today, the dominant material of civilization is information; and the dominant tool is

electronic interchange. In this age of shared knowledge, people and systems transform

information into better products and services.

Nearly every job in every company is changing in some way as a result of shared

knowledge in the information age. Computer systems and intelligent machines are as

much an influence today as were the stone, bronze, or iron tools of the past.

The unique expertise of CASA/SME is understanding information technology and the

ways this technology can empower people in the manufacturing enterprise. Indeed, a key


15

function of the Wheel is to illustrate ways in which computer systems support people

and processes in the enterprise.

The CASA/SME Industry LEAD Award (Leadership and Excellence in the Application and

Development of CIM) is given each year to a manufacturing company that exemplifies

enterprise integration. The CASA/SME-sponsored AUTOFACT Conference and

Exposition is the world's leading showcase of CAD, CAM, and other systems for

product and process definition and manufacturing.

4) Processes:

The manufacturing enterprise combines people and tools, in processes, to add value

to purchased materials and components. Processes are the life of the manufacturing

enterprise.

The real manufacturing enterprise might have hundreds or thousands of processes,

depending upon the level of detail. In the new Wheel, there are three main groups of

processes, a trinity of actions focused on customer satisfaction. These are

product/process definition, manufacturing, and customer support.

First is product/process definition. It defines what is to be built and how it is to be built.

While product/process definition may consume only 5 to 20 percent of the

manufacturing enterprise's total resources, it casts a long shadow. When product and

process definition is complete, the ultimate performance and value of the product, as

well as most manufacturing expenses, have already been determined.

Second is the lower segment of the wheel, manufacturing. For products like

automobiles, industrial equipment, office equipment, and appliances, manufacturing

requires the largest investment of resources.

Third are processes which, combined with the manufactured product, make it available

and useful to the customer. These customer support processes include global support,

distribution, sales and promotion, and customer service throughout the product life cycle.

The three main process groups are further divided. Together, all 15 processes form a

Manufacturing Enterprise value chain:

PRODUCT/PROCESS DEFINITION:

1) Business Definition

2) System Design


16

3) Component Design

4) Continuous Improvement

5) Documentation and Release

MANUFACTURING (/Service)

6) Resource Planning

7) Operations Planning

8) Component Fabrication

9) Assembly and Test

10) Material Management

CUSTOMER SUPPORT

11) Global Organization

12) Distribution

13) Sales and Promotion

14) Customer Services

15) Life-Cycle Transitions


17

SIMILARITIES IN CASA/SME CIM Wheels:

In middle rim of the wheel shows the product, process and manufacturing facility

requirements for the CIM implementation.

The wheels clearly define the resource required for complete implementation of

CIM.

The islands of CIM WHEEL are same for Designing and manufacturing in all.

The wheels are customer requirement oriented so are showing proper policy of

manufacturing.

DIFFERENCE BETWEEN CIM WHEEL AND CIM ENETERPRISE WHEEL:

The CIM wheel more emphasis on information system, Design

Manufacturing,Business.Segment where as the CIM Enterprise Wheel emphasis on

customer satisfaction ,knowledge management ,Globalization.

The CIM Wheel is also concentrated on the factory automation side that portion was

not included in CIM Enterprise Wheel.

In CIM Wheel there is no portion to taking into account the customer satisfaction,

where as in the CIM Enterprise Wheel customer satisfaction was taken into account

as a key factor.

The organizational goals were set out in the CIM Enterprise Wheel, where as in CIM

wheel only Operational and financial matter can be clear out only.

IMPLIMENTATION AND INTEGRATION OF CIM:

CIM IMPLEMENTATION:

Integration and adaptability are the key issues of the implementation process of CIM.

Therefore, it is appropriate to discuss the main elements of integration and adaptability of

CIM and how these issues should be taken into account during the implementation of CIM.

The integration of systems is frequently hindered by the resistance to converge the activities

of different functions within the business. Organizational integration and the elimination of

departmental barriers are proving to be more difficult to achieve in practice and will in turn

hinder the technical development of the ` seamless‘ integration required.

The integration of computer- aided design (CAD) and CNC machines made a huge

impact on the development of CIM. In support of the critical roles that humans play in the


18

success of CIM, the most common recommendation found in almost all recent literature is

the dire need for education and training in relation to the adoption of CIM. It could even

mean a redefinition of responsibilities from the top to the bottom of the organization.

Research in CIM design and implementation has mainly been in the area of production.

However, the major issues in CIM are directly related to information systems.

A conceptual model illustrating the integration and adaptability issues of implementing CIM

is presented in Figure 1. The organization has to develop a strategy which bests the

environment in which it operates. The model explains the importance of the alignment

between various implementation strategies for improving integration and adaptability of CIM.

For instance, strategic level issues such as the alignment between business and manufacturing

strategies require suitable organizational structure, technology, employee involvement and

the nature of production planning and control system. Therefore, this relation-ship is

represented by the closed loop as shown in Figure 1, to explain the interaction and

dependency between managerial, technological and operational level issues. There is a

number of organizational issues which companies meet when analyzing, designing and

managing the implementation of CIM systems.

The strategy for the successful implementation of CIM should include the use of

computers for integrating information and material, small batch production with on- line

production control system (e.g. FMS) , and a local area network (LAN) for integrating the

information within the organization. A conceptual framework is presented in Figure 2 to

explain the main issues involved in improving the integration and adaptability aspects of CIM.

The model presents a set of major elements of CIM implementation that includes strategic,

organizational, behavioral, technological and operational issues. Each of these elements is

discussed from the view of improving integration and adaptation in the implementation of

CIM. The details follow here under.

Strategic aspects:

Top management selects CIM as a manufacturing strategy based on the business

strategy considering the internal and external factors. Middle management should work out

the CIM development programme. The workers along with middle management are

responsible for the implementation of CIM. The company‘s limitations in terms of capital,

knowledge workers, complexity of the material, layout types, etc. should be considered while


19

designing and implementing CIM. In addition, the achievement of objectives should be used

to justify the adoption of CIM technology.

Organizational aspects:

CIM requires cross- functional co-operation, and high involvement of employees in

product development process. To be successful in the implementation of CIM, an initiative

must have the direct involvement and commitment of top management. Top management

also invests company resources and accepts long- term results, by eventually modifying the

company organization as required for a successful CIM. Effective implementation of CIM

requires a strong degree of communication and co-ordination among interdependent units in

companies.

The internal factors such as product and process characteristics, infrastructure and

skills available. The external factors such as market characteristics, government support and

regulations tremendously in the implementation process of CIM.

Behavioral aspects:

Co-operation among different levels of employees can be achieved by smoother

communication systems. The type of workforce involved in the implementation and

operation of CIM is knowledge workers such as computer operators, software engineers, and

network managers and so on. Therefore, the type and level of training and education

required should be determined taking into account the infrastructure, integration and

adaptability issues. Effective teamwork (with empowerment and responsibility) has to be

achieved to successfully implement CIM. This could be achieved by a collective incentive

scheme, team work, training and job enrichment.

Technological aspects:

A suitable CIM configuration should be decided before the implementation process

that generally centers around the identification of tasks to computerize, the selection of

feasible software packages, and improving software compatibility. In order to include

flexibility in CIM, manual policies, procedures, and practices should be established. The

integration and adaptability of CIM can be made considerably easier with FMS, cellular

manufacturing systems and JIT production systems. Technologies such as Internet,

multimedia and LAN can be used to improve the integration of various business areas of

manufacturing organizations. Automated guided vehicle systems (AGVs) using computers

can play an important role in improving the integration of material flow within the


20

Production system. Integration of operational activities with suppliers can be improved by

on- line computer information systems such as an electronic data interchange (EDI). These

also can play a vital role in an unmanned factory.

Operational aspects:

CIM requires the reorganization of the production planning and control system with

an objective to simplify the material and information flows. The manufacturing concepts

such as JIT and MRP II and technologies such as CE and AGVs provide the base for easy

implementation of CIM to improve integration and adaptability. The essence of CE is the

integration of product design and process planning into one common activity, that is CAD/

CAE. Concurrent design helps to improve the quality of early design decisions and has a

tremendous impact on the life cycle cost of the product. The implementation of CE will

facilitate integration and adaption in CIM.


21

INTEGRATION:

( I ) CIM should be implemented only after the basic foundations are put in place in the

com-pany. It may bemore productive to redesign the organizational structure before

implementing available technology than to hope the technology will, bring about

manufacturing effectiveness. Simplification of information and material establish a solid

foundation for adopting CIM technology.

( ii ) Integration and adaptability issues of CIM should be evaluated considering the lack of

knowledge about CIM and its potential, strategic implications of longer term planning, etc of

delaying CIM implementation on company competitiveness and the etc of operations

integration.

( iii ) The integration and adaptability issues of CIM are in uenced by factors such as the

required hardware platform, integration requirements, and data processing skills. Therefore,

there is a need to consider these factors while implementing CIM. Knowledge workers such

as computer operators and software engineers, and a multifunctional workforce are essential

to improve integration and adaptation in the implementation of CIM.

( iv ) Human workers play a significant role in influencing the integration and adaptability

issues of CIM especially by co-operative supported work. This reveals the importance of

providing a comprehensive training to equip workers with the knowledge of automation,

computer technologies, and manufacturing process.

( v ) Despite the arguments regarding exibility of CIM, the experience from practice is that

automation is frequently too rigid to adapt to changing market needs and the production of

new products. This indicates the importance of exibility of CIM while designing the system

and re-organization of the production planning and control system.

( vii ) There is a need for a unique set of standards that satires‘ all the requirements of a CIM

system.

The answer to both the questions just posed is no. the starting point for CIM is not islands

of automation or software, not is it the structure presented by the CIM wheel, rather it is a

company’s business strategy.

System modeling tools

It is helpful if the modeling tool is of sufficient sophistication that it exists in three forms:

As a representation of the system

As a dynamic model

As an executable model


22

IDEF (Integration Definition for Function Modeling)

IDEF initially provided three modeling methods

IDEF0 is used for describing the activities and functions of a system

IDEF1 is used for describing the information and its relationships

IDEF2 is used for describing the dynamics of a system

Activity cycle diagrams

This modeling approach follows the notation of IDEF0 by having activities

represented as rectangles and by having the activity names specified inside the rectangle. All

resources which are to be represented in the model are classified as entity classes.

CIM open system architecture (CIMOSA)

CIMOSA was produced as generic reference architecture for CIM integration as part

of an ESPRIT project. The architecture is designed to yield executable models or parts of

models leading to computerized implementations for managing an enterprise.

Manufacturing enterprise wheel

The new manufacturing enterprise wheel‘s focus is now the customer at level 1, and

it identifies 15 key processes circumferentially at level 4. These are grouped under the

headings of customer support, product/process and manufacturing.

CIM architecture

Data dictionary

Data repository and store

A layered structure

Repository builder

Product data management (PDM): CIM implementation software

The four major modules typically contained within the PDM software are

Process models

Process project management

Data management

Data and information kitting

The PDM environment provides links to a number of software packages used by a

company. They are

A CAD package

A manufacturing/production management package

A word processing package


23

Databases for various applications

Life-cycle data

Communication fundamentals

A frequency

An amplitude

A phase which continuously changes

A bandwidth

An introduction to baseband and broadband

Telephone terminology

Digital communications

Local area networks

Signal transmission, baseband and broadband

Interconnection media

Topology

Star topology

Ring topology

Bus topology

Tree topology

LAN implementations

Client server architecture

Networks and distributed systems

Multi-tier and high speed LANs

Network management and installation

Security and administration

Performance

Flexibility

User interface

Installation

Opportunities include:

• "Best Practice" focus emerging in the industry.

• Opportunity to undertake Global benchmarking.


24

Main Threats and Restraints are:

• Intra-industry competition for funding (both levy and matching).

• Industry apathy/scepticism.

BENEFITS OF CIM :

A reduction in inventory translates into higher profits.

Tangible Benefits:

Higher Profits, less direct labor ,Increased machine utilization ,Reduced scrap

and rework ,Increased factory capacity ,Reduced inventory ,Shortened new

product development time, Decreased warranty costs, Shorter lead times for all

process.

Intangible Benefits :

Higher employee moral ,Safer working environment ,Improved customer iage

,Greater Scheduling flexibility ,Grater ease in recruiting new employees, Increased

job security ,Moral opportunities for upgrading skills.

CIM I & II:

Fundamental concept of information and communication technology like Computers,

communication and database systems. In CIM-I 4th generation of computer is used and is

called as CIM-I.LSI and VLSI technology is used for CIM-I.

In CIM-II the main focus is on flexibility in automated processes of manufacturing that are

characterized by the operation of NC-Machines and industrial robots. Typical systems of the

flexible automation are FMC (Flexible manufacturing cells), flexible production lines,

Flexible production systems. The parallel processing is done in CIM-II with Designing and

Modeling or Analysis.


25

EDI : Electronic Data Interchange

Electronic Data Interchange (EDI) is simply a set of data definitions that permit business

forms that would have been exchanged using paper in the past, to be exchanged

electronically. This simple set of definitions has spurred a number of components of an

industry to put in place an operational environment in which the exchange of electronic form

data substitutes for the exchange of paper forms of data. This has resulted, in some cases, in

the establishment of an EDI environment, which arguably represents the most advanced

state of computer integrity today, causing some to view EDI and CIM as one and the same.

We view EDI only as a subset of electronic commerce applied in manufacturing, albeit a very

important one. As such, EDI provides an excellent example of a working in an intelligent

environment and is a good starting point for application in CIM.

Electronic data interchange aims at single point collection of data for use by various

departments participating in an industrial activity.

CIM I & II


26

OBJECTIVE

The basic documents for transaction of manufacturing data will be taken only once by one

department of industry and other departments will take the information from the first one

electronically, avoiding the need to either physically take the document from one office to

another or keying in the data again and again involving the attendant problems of manual

labor and errors creeping in at each stage of data entry etc….

FUTURE SCENARIO

It should be possible to create a few or even a single message/document for the entire

process of manufacturing in the course of Automated manufacturing.

Once VSAT connectivity is established with all Customs / Excise formations in India, all

modal verifications, end use certificate, re warehousing certificate for transfer of material,

TRA's could be made immediately. Above all there would be uniformity in assessment

decision all over India.

EDI is a way of business life. It is based on the principle of trust and contractual obligations.

Once Evidence act and other laws of the land recognize. EDI transactions and provide for

the same by fast settlement of disputes, it should be possible to do away with requirements

for paper documentation, i.e., there would be no necessity to submit product design

,manufacturing data ,scheduling ,material handling path generation etc in paper. Records

need only be kept at the offices of Importers / Exporters for a minimum period, for

verification by concerned authorities, if required. Since EDI is based on trust, there would

be no need for examination of cargo in a routine manner , the facility of Green Channel

would apply to almost 80% of cases of regular Importers with a clean tract record.

Therefore it is essential that Govt., trade and transporters recognize the likely benefits and

move forward to establish a regime of mutual trust and confidence.


27

Electronic Data Inter-change (EDI) is a way of business life, which thrives in an

environment based on trust of faith, whereas in the present manual system the procedures

and practices are all based on lack of trust and faith. Attitudinal change in the officers and

the business people is required to adopt to EDI. EDI is a reality, EDI cannot be introduced

in a significant way unless we have complete overhaul of working system, methods and

procedures. Above all unless the Laws/Acts governing business in the country are amended

to recognize EDI transactions, full-fledged EDI is not possible. Unless sincere efforts are

made to transform the working environment, with a distinct positive attitude we would be

left behind in the interest of the nations economic prosperity we adopt ourselves to global

scenario and move towards paperless transaction system.

Definition and Use of EDI. EDI is the computer-to-computer interchange of strictly

formatted messages that represent documents other than monetary instruments. EDI implies

a sequence of messages between two persons, person and machine, machine and person,

machine and machine either of whom may serve as originator or recipient. The formatted

data representing the documents may be transmitted from manufacturer to recipient via

telecommunications or physically transported on electronic storage media.

In EDI, the usual processing of received messages is by computer only. Human intervention

in the processing of a received message is typically intended only for error conditions, for

quality review, and for special situations. For example, the transmission of binary or textual

data is not EDI as defined here unless the data are treated as one or more data elements of

an EDI message and are not normally intended for human interpretation as part of on-line

data processing.

Standards Required for EDI. From the point of view of the standards needed, EDI may

be defined as an interchange between computers of a sequence of standardized messages

taken from a predetermined set of message types. Each message is composed, according to a

standardized syntax, of a sequence of standardized data elements. It is the standardization of

message formats using a standard syntax, and the standardization of data elements within the

messages, that makes possible the assembling, disassembling, and processing of the messages

by computer.


28

Implementation of EDI requires the use of a family of interrelated standards. Standards are

required for,

(a) The syntax used to compose the messages and separate the various parts of a message,

(b) Types and definitions of application data elements, most of variable length,

(c) The message types, defined by the identification and sequence of data elements forming

each message, and

(d) The definitions and sequence of control data elements in message headers and trailers.

Additional standards may define:

(e) A set of short sequences of data elements called data segments,

(f) The manner in which more than one message may be included in a single transmission,

and

(g) The manner of adding protective measures for integrity, confidentiality, and

authentication into transmitted messages.

The Long-Range Goal for EDI Standards. There are several different EDI standards in

use today, but the achievement of a single universally-used family of EDI standards is a long-

range goal. A single universally-used family of standards would make use of EDI more

efficient and minimize aggregate costs of use. Specifically, it would (a) minimize needs for

training of personnel in use and maintenance of EDI standards, (b) eliminate duplication of

functionality and the costs of achieving that duplication now existing in different systems of

standards, (c) minimize requirements for different kinds of translation software, and (d) allow

for a universal set of data elements that would ease the flow of data among different but

interconnected applications, and thereby maximize useful information interchange.


29

Application:

Examples of applications (not necessarily the subject of current standards) are:

a. vendor search and selection: price/sales catalogs, bids, proposals, requests for

quotations, notices of contract solicitation, debarment data, trading partner profiles;

b. contract award: notices of award, purchase orders, purchase order

acknowledgments, purchase order changes;

c. product data: specifications, manufacturing instructions, reports of test results,

safety data;

d. shipping, forwarding, and receiving: shipping manifests, bills of lading, shipping

status reports, receiving reports;

e. customs: release information; manifest update;

f. payment information: invoices, remittance advices, payment status inquiries,

payment acknowledgments;

g. inventory control: stock level reports, resupply requests, warehouse activity

reports;

h. maintenance: service schedules and activity, warranty data;

i. tax-related data: tax information and filings;

j. insurance-related data: health care claim; mortgage insurance application;

k. other government activities: communications license application; court conviction

record; hazardous material report; healthcare event report.

BENEFITS OF EDI:

More Secure than paper

Cost savings

Acknowledgements from receiving institution

Speed

Easy partner exchange each term

Automated transfer articulation

Small file size


30

AIM: TO STUDY INTRODUCTION TO FMS, FLEXIBILITIES IN FMS AND ITS

MEASUREMENT CRITERION.

FMS :

FMS is an integrated approach to automating a production. The primary

characteristic of an FMS is that it is a computer-controlled manufacturing system that

ties together storage, manufacturing machines, inspection, tooling, and materials

handling equipment. The FMS is designed to be flexible so that it can manufacture a

variety of products at relatively low volumes, with minimum lead time between

product changes.

A flexible manufacturing system is highly automated GT machine cell, consisting of

group of processing workstation, interconnected by automated material handling and

storage system and controlled by distributed computer system. The reason the FMS

is called flexible is that it is capable of processing a variety of different part, systems

and quantity of production.

An FMS relies on principle of group technology. No manufacturing system can be

completely flexible. These are limits to the range of parts or products that can be

made in an FMS.

A more appropriate term for an FMS would be flexible automated system to

differentiate it from manned GT machine cell of conventional transfer line.

NEED OF FMS

The key objective in manufacturing is to get the right raw materials or to the right

machines at the right time.

GANPAT UNIVERSITY



COMPUTER INTEGRATED M M. T .

EXPERIMENT NO: 2 DATE: ..../..../........

ECH CAD- CAM

ANUFACTURING ( 3 ME1 1 5 )


31

Examples indicate the underutilization of equipment and gross inefficiencies existing

in a vast majority of Manu factoring industries. The common day to day disturbances within

overall manufacturing process consisting of:

1. Priority changes

2. Eng. Design changes

3. Tooling difficulties

4. Machine breakdowns

5. Processing problems

6. Lost, Misplaced and scrapped parts

7. Vendor lateness

What is needed in today‘s competitive environment, regardless of what products a

particular company make. This implies that:

1. There should be minimum delay between order placement and order delivery.

2. Quality and reliability should be high.

3. Operating costs should be predictable and under control.

4. Replacement parts should be available and accessible on a quick turnaround basis.

OBJECTIVES OF FMS :

1. Improve operational control through :

Reduction in the number of uncontrollable variables.

Providing tools to recognize and rect quickly to deviations in the

manufacturing plan

Reducing dependence on human communication

2. Reduce direct labor through :

Removing operators from the machining site.

Eliminating dependence on highly skilled machinists

Providing a catalyst to introduce and support unattended or lightly

attended machine operation

3. Improve short-run responsiveness consisting of :

Engg. Changes

Processing changes


32

Machine downtime of unavailability

Cutting tool failure

Late material delivery

4. Improve long-run accommodations through quicker and easier assimilation of :

Changing product volumes

New product additions and Introductions

Different part mixes

5. Increase machine utilization by :

Eliminating machine setup

Utilizing automated features to replace manual intervention

Providing quick transfer devices to keep machines in the cutting

cycle

6. Reduce inventory by :

Reducing lot sizes

Improving inventory turnovers

Providing the planning tools for just-in-time manufacturing

AREAS OF APPLICATIONS OF FMS :

The FMS is applicable in other manufacturing & machining:

Assembly of equipments

Semiconductor component manufacturing

Plastic injection molding

Sheet metal fabrication

Welding

Textile machinery manufacture

Such systems have proved to be practical and economical for applications with the

following characteristics:

Families of parts with similar geometric features for require similar types of

equipment and processes

A moderate number of tools and processes steps

Moderate precision requirements


33

TYPES OF FMS

Having considered the issue of flexibility let us now consider the various types of

flexible manufacturing systems. Each FMS is designed for a specific application, that is, a

specific family of parts and processes. Therefore, each FMS is custom-engineered and unique.

Given these circumstances, one would expect to find a great variety of system designs to

satisfy a wide variety of application requirements.

Flexible manufacturing system can be distinguished according to following.

Number of machines.

Level of flexibility

Number of machines.

Flexible manufacturing system can be distinguished according to the number

of machines in the system. The following are typical categories:

Single machines cell,

Flexible manufacturing cell, and

Flexible manufacturing system.

A single machines cell consists of one CNC machining center combined

with a parts storage system for unattended operation. Completed parts are

periodically unloaded from the parts storage unit, and raw work parts are loaded into

it. The cell can be designed to operate in a batch mode, a flexible mode, or a

combination of the two. When operated in a flexible mode, the system satisfies three

of the four flexibility tests. It is capable of (1) processing different part styles, (2)

responding to changes in production schedule and (4) accepting new part

introductions. Criterion (3), error recovery, cannot be satisfied because if the single

machine breaks down, production stops.

A flexible manufacturing cell (FMC) consists of two or three processing

workstations (typically CNC machining centers or turning centers) plus a parts

handling system. The parts handling system is connected to a load/unload station.

The handling system usually includes a limited parts storage capacity.

A flexible manufacturing system (FMS) has four or more processing

stations connected mechanically by a common parts handling system and

electronically by a distributed computer system. Thus, an important distinction


34

between a FMS and a FMC is in the number of machines: a FMC has two or three

machines, while a FMS has four of more. There are usually other differences as well.

One is that the FMS generally includes nonproccesing workstations that support

production but do not directly participate in it. These other stations include

part/pallet washing stations, coordinate measuring machines, and so on. Another

difference is that the computer control system of a FMS is generally larger and more

sophisticate, often including function not always found in a cell, such as diagnostics

and tool monitoring. These additional functions are needed more in a FMS than in a

FMC because the FMS is more complex.

A dedicate FMS is designed to produce a limited variety of part styles, and

the complete universe of part to on the system is known in advance. The part family

is likely to be based on product commonality rather than geometric similarity. The

product design is considered stable, so the system can be designed with a certain

amount of process specialization to make the operation more efficient. Instead of

being general propose the machines can be designed for the specific processes

required to make the machine sequence may be identical or nearly identical for all

parts processed, so a transfer line may be appropriate, in which the workstations

possess the necessary the machine sequence may be identical or nearly identical for

all parts processed, so a transfer line may be appropriate, in which the workstations

possess the necessary a transfer line may be appropriate, in which the workstations

possess the necessary flexibility to process the different parts in the mix.

A random-order FMS is more appropriate when the part family is large,

there are substantial variations in part configurations, new part designs will be

introduced into the system and engineering changes will occur in parts currently

produced, and the production schedule is subject to change from day to day. To

accommodate these variations, the random-order FMS must be more flexible than

the dedicated FMS. It is equipped with general purpose machines to deal with the

variations in product and is capable of processing parts in various sequences (random

order). A more sophisticated computer control system is required for this FMS type.


35

FMS LAYOUT CONFIGURATION :

The material handling system establishes the FMS layout. Most layout configuration

found in today's FMS can be divided into five categories.

In-line layout.

Loop layout.

Ladder layout.

Open Field layout.

Robot Controlled cell

Computer control system:

The FMS includes a distributed computer system that is interfaced to the workstation,

material handling system and other hardware components. A typical FMS computer system

consists of central computer components. The various control requirements are:

1. Workstation control

2. Distribution of control instruction to work station

3. Production cycle

4. Shuttle control

5. Traffic control

6. W/p monitoring

7. Tool control

8. Performance monitoring & reporting

9. Diagnostics

HUMAN RESOURCES:

One additional component in the FMS is human labor. The use of manpower in FMS is

attributed to the following functions.

Loading/unloading

Changing & setting tools

Maintenance & repair

NC part programming

Overall management of system


36

FMS BENEFITS :

A number of benefits expected in successful FMS application.

Increase machine utilization.

Fewer machine required.

Less factory floor space required.

Lower manufacturing lead times.

Reduced inventory requirements.

Reduced direct labor requirements & higher productivity.

So for high productivity for all batch size, large of small

Lower storage costs.

Reduced labor if not altogether avoiding labor.

reduced handling

flexible production system to incorporate product changes

At short notice to meet customer's specific requirements.

Unity for unattended production.

FLEXIBLITY IN FMS:

Types of Flexibility in FMS are as following :-

1. Machine Flexibility

2. Process Flexibility

3. Product Flexibility

4. Routing Flexibility

5. Volume Flexibility

6. Expansion Flexibility

7. Operation Flexibility

8. Production Flexibility

[1] Machine Flexibility

"Ease of making change required to produce a given set of part type."

Depends of Factors:

Setup or change over time.


37

Ease of machine reprogramming (ease with which part program can be

downloaded to machine).

Tool storage capacity of machines.

Skill and versatility of workers in the system.

Measures:

Time to replace worn-out or broken cutting tools.

Time to change tools in a tool magazine.

Time to assemble or mount the new fixtures.

Machine tool setup time

- Tool preparation

- Part positioning and releasing

- NC part program change over

How to attain machine flexibility?

By using sophisticated tool-loading and part loading devices(technological

progress)

Minimize tool changes (proper operation assignment)

Bring the part and required tool together to the machine (technological

capability)

[2] Process Flexibility

"Ability to produce a given set of part types in several ways"

Depends on Factors:

Machine flexibility

Skills of workers

Measure:

The number of part types that can be simultaneously processed without using

batches.

How to attain process flexibility?

By using machine flexibility

By using Multi-purpose, adoptable, and CNC machining centers.


38

[3] Product Flexibility

"Ability to change over to new set of products economically and quickly."

Depends on Factors:

How closely the new part design matches the existing part family

Off-line part program preparation

Machine flexibility

Measure:

The time required from one part mix to another


By using an efficient and automated production planning and control system

which containing.

(i) Automatic operation assignment procedure

(ii) Automatic pallet distribution calculation capability

By using machine flexibility.

[4] Routing Flexibility

"Ability to handle breakdowns (machines, tools, etc)."

- Either a part type can be processed via. Several routes

OR

- Equivalently, each operation can be performed on more than one machine

Routing flexibility is of two types:

(i) Potential: - part route are fixed but parts are automatically rerouted

when a breakdown occurs

(ii) Actual: - Identical parts are actually processed through different

routes, independent of breakdown.

Depends on Factors:

Similarity of parts in the mix.

Similarity of workstation.

Duplication of workstation.

Cross training of manual workers.

Common tooling.


39

Measure :

Robustness of FMS (Continuity of production)


By allowing automated and automatic rerouting of parts (potential routing

flexibility)

Pooling machines into machine groups

Duplicating operation assignments (Actual routing flexibility)

[5] Volume Flexibility

"Ability to operate an FMS profitable at different production volume"

Depends on Factors :

Level of manual labor performing production

Amount invested in capital equipment

Measure :

Smallest volumes for all part types that allow the system run profitably

How to attain volume flexibility ?

By using multi purpose machines

Layout not dedicated to a particular process

By using sophisticated, automated materials handling system, e.g. intelligent

carts (not fixed-route conveyors)

Though routing flexibility

[6] Expansion Flexibility

"Ease of modularly expanding a system"


Expense of adding workstation

Ease with which layout can be expanded

Type of part handling system used

Ease with which properly trained workers can be added


40

Measure :

How long the FMS can become


Non-dedicated, non-process driven layout

Flexible materials handling system containing wire guided carts

Modular flexible machining cells with pallet changers

Through routing flexibility.

[7] Operation Flexibility

"Ability to interchange the ordering of (some) operations for each part type"


Machine flexibility

Interchangeability of operation

Sequence of operation

Measure :

Ability and extent of not pre-determining the order of all operations, each on

a particular machine (type)


Design a decision system to make decision in real-time determining the 'next'

operation and the 'next' machine, depending on the system state (idle, busy,

bottleneck) of various elements of FMS

Through machine flexibility.

[8] Production Flexibility

"The universe of part types that the FMS can produce"


Machine flexibility of individual station

Range of machine flexibilities of all stations in the system

Measure :

Level of existing technology



41

Increase the level of technology

Increase the versatility of the machine tools

All previous flexibilities.

MEASUREMENT OF VOLUME FLEXIBILITY

Volume Flexibility

Volume Flexibility is defined as an ability to economically produce parts in high and

low total quantities of production, given the fixed investment in the system.

It also defined as an ability of a manufacturing system to be operated profitably at

different overall output levels, thus allowing the system to adjust production within a wide

range. Different factors which act on volume flexibility system are as followings :

1) level of manual labour performing production.

2) Amount invested in capital equipment.

Following are the aspects for which product flexibility is working :

1) Change in production rate in the past & present production levels.

2) Ability to utilized space capacity in case of order shortage.

3) In case of under demand utilizing capacity with time rescheduling.

4) In case of order shortage cost incurred for rescheduling.

5) Increment the investment for leading time.

6) Extra cost involved in sub contracting.

7) Cost implication for lost order in past due to over demand.

8) Extra cost generated due to overtime, deteriorated quality or increased

breakdown to meet the demands.

9) To minimize fluctuation of demand adopt different strategy.

Product flexibility measurement

Product flexibility is reflected by the ease with which new parts can be added or

substituted for existing parts. Product flexibility helps the firm to respond to the market by


42

enabling it to bring newly designed products quickly to the market. It is measured through

the response through the response to the question on the following aspects.

a) Varity of products being manufactured

b) Frequency of producing new products.

c) No. Of new products introduced at various intervals.

d) Time & cost required to change tooling and software to accommodate

different products.

e) Major change made in product design.

f) Minor change made in product design.

Now here there is an example of volume flexibility is as follow :

SOLVED PROBLEM

(1) A survey is carried out for three companies (X,Y, & Z) for finding the status of

volume flexibility within their company. the score of different aspects as written

above are mention in the following table-1 based on the questionnaire for the aspects.

The weightage of each parameter towards volume flexibility has been determined by

calculating eight vectors & normalizing it. Table-2 shows the contribution of

different factors towards flexibility.

Aspects

(Parameters)

A B C D E F G H I

Score of X

2 3 3 1 4 3 4 2 4

Score of Y

1 4 3 2 3 4 3 3 2

Score of Z

2 2 4 4 3 4 2 3 3


43

Aspects

(Parameters)

A B C D E F G H I

Weightage For

X .4395 .0193 .0122 .0257 .1233 .2151 .0167 .0394 .1084

Weightage For

Y .0111 .0286 .4531 .0182 .0156 .0398 .1102 .1123 .2121

Weightage For

Z .2222 .1005 .1204 .0288 .0111 .0152 .4423 .0211 .0101

Find the volume flexibility for three companies and its average value. Show volume

flexibility for three companies X,Y, & Z.

Solution:

The volume flexibility =

Where, Wx is the weightage of Xth. Factor, and

Sx is the score of question based on Xth factor.

Note : Based on this, volume flexibility values of surveyed enterprise are found in a scale of

0 to 1 so found out.

For Company X :


Based on above equation,

VFx = [(0.4395 x 2) / 4] + [(0.0193 x 3) / 4] + [(0.0122 x 3) / 4] + [(0.0257 x 1) / 4] +

[(0.1223 x 4) / 4] + [(0.2151 x 3) / 4] + [(0.0167 x 4) / 4] + [(0.0394 x 2) / 4] +

[(0.01084 x 4) / 4]

= 0.21975+0.014475+0.00915+0.006425+0.1233+0.161325+0.0167+0.0394+0.1084

= 0.698925

VFx = 0.70

4

x xw s

4

x xw s


44

For Company Y :



VFy = [(0.0111) / 4] + [(0.0286 x 4) / 4] + [(0.4531 x 3) / 4] [(0.0182 x 2) / 4] +

[(0.0156 x 3) / 4] + [(0.0398 x 4) / 4] [(0.1102 x 3) / 4] [(0.1123 x 3) / 4] +

[(0.2121 x 2) / 4]

= 0.002775+0.0286+0.009718995+0.0091+0.0117+0.0398+0.08265+0.084225

+ 0.10605

= 0.37461

VFy = 0.375

For Company Z :



VFz = [(0.2222 x 2) / 4] + [(0.1005 x 2) / 4] + [(0.1204 x 2) / 4] + [(0.0288 x 2) / 4] +

[(0.0111 x 3) / 4] + [(0.0152 x 4) / 4] + [(0.4423 x 2) / 4] + [(0.0211 x 3) / 4] +

[(0.0101 x 3) / 4]

= 0.1111+0.05025+0.1204+0.0288+0.008325+0.0152+0.22115+0.015825+0.007575

= 0.578625

VFz = 0.58

Now, average value of volume flexibility for companies X,Y,Z is,

3

x y zVF VF VF

aVF

VFa = [(0.70 + 0.375 + 0.58)/3]

VFa = 0.55167

VFa = 0.552

4

x xw s

4

x xw s


45

(2) A survey is carried out for three companies (P, Q, and R) for finding the status of

product flexibility within their company. The scope of different aspects (as written

above) are mentioned in the following table-1, based on the questionnaire prepared

for these aspects. The weightage of each parameter towards product flexibility has

been determined by calculating. Eigen vector and normaling it. Table-2 shows the

contribution of different factors towards product flexibility.

Aspects

(Parameters)

a

b

c

d

e

f

Score of P

1 3 2 1 4 3

Score of Q

1 3 4 2 4 4

Score of R

2 2 1 4 3 4

Table-1

Aspects

(Parameters)

a

b

c

d

e

f

Weightage For

P 0.1605 0.1331 0.0747 0.5187 0.1125 0.00036

Weightage For

Q 0.1595 0.1055 0.0858 0.6071 0.2111 0.00122

Weightage For

R 0.2021 0.00095 0.5567 0.0785 0.1423 0.1795

Table-2


46

Find the product flexibility for three companies and its average value. Show product

flexibility and their status on histogram for three P,Q, and R

Solution :

The product flexibility =

where, Wx is the Weightage of Xth factor, and

Sx is the score of question based on Xth factor.

Note : Based on this, product flexibility values of surveyed enterprise are found on

a scale of 0 to 1 is found out.

For Company P :


Based on the above equation.

VFp = [(0.1602 x 1) / 4] + [(0.1331 x 3) / 4] + [(0.0747 x 2) / 4] + [(0.2187 x 1) / 4] +

[(0.1125 x 4) / 4] + [(0.00036 x 3) / 4]

VFp = 0.040125+0.099825+0.03735+0.129675+0.1125+0.00027

= 0.419745

VFp = 0.42

For Company Q :



VFQ = [(0.1595 x 1) / 4] + [(0.1055 x 3) / 4] + [(0.0858 x 4) / 4] + [(0.6071 x 2) / 4] +

[(0.2111 x 3) / 4] + [(0.00122 x 4) / 4]

4

x xw s

4

x xw s

4

x xw s


47

VFQ = 0.039875+0.079125+0.0858+0.30355+0.158325+0.00122

= 0.667895

= 0.67

For Company R :



VFR = [(0.2021 x 2) / 4] + [(0.00095 x 2) / 4] + [(0.5567 x 1) / 4] + [(0.0785 x 1) / 4] +

[(0.1423 x 3) / 4] + [(0.1795 x 4) / 4]

VFR = 0.10105+0.000475+0.139175+0.0785+0.106725+0.1795

= 0.605425

VFR = 0.61

Now, average value of product flexibility for companies X,Y, and Z is,

3

P Q RVF VF VF

aVF

VFa = [(0.42 + 0.67 + 0.61) / 3]

VFa = 0.5666667

VFa = 0.567

4

x xw s


48

AIM: TO STUDY QUANTITATIVE ANALYSIS OF FMS USING BOTTLENECK

MODEL.

INTRODUCTION:

Implementation of an FMS represents a major investment and commitment by the

user company. It is important that the installation of the FMS system be precede by

thorough planning and design, and that its operation characterized by good management for

all resources: machines, tools, pallets, parts, and people. But there are always some issues

relating with the FMS planning, design, and operations. Most of the operational, and design

related FMS problems can be addressed using quantitative analysis techniques. FMSs have

constituted an active area of interest in operations research, and many of the important

contributions that are included in list of references.

Classification of Quantitative Analysis:

FMS analysis techniques can be classified as follows:

(1) Deterministic models.

(2) Queuing models.

(3) Discrete Event Simulation.

(4) Other approaches, including heuristics.

DETERMINISTIC MODELS:

To obtain starting estimates of the system performance, deterministic models can be

used. The deterministic modeling approach is useful in the beginning stages of FMS design

to provide rough estimates of system parameters such as production rate, capacity, and

utilization. Deterministic models do not permit evaluation pf operating characteristics such

as the build up of ques and other dynamics that can impair performance of the production

system. Consequently, deterministic models tend to overestimate FMS performance.

GANPAT UNIVERSITY



COMPUTER INTEGRATED M M. T .


ECH CAD- CAM



49

On the other hand, if actual system performance is much lower than the estimates

provided by these models, it may be a sign of either poor system design or poor management

of the FMS operation.

Queuing Models:

Queuing models can be used to describe some of the dynamics not accounted for in

deterministic approaches. These models are based on the mathematical theory of queues.

They permit the inclusion of queues, but only in a general way and for relatively simple

system configurations. The performance measures that are calculated are usually average

values for steady-state operation of the system. Probably the most well known of the FMS

queuing model is CAN-Q, that is closed queuing network and developed by Soldberg in

1978. Kimemia and Gershwin in 1978 have presented an optimization model with work

center level complexity (i.e., with all machines at a work center having the same process

time for all part types) for an open-queuing network. Secco Suardo coupled a non-linear

programming formulation with a closed-queuing network model for a single class of

jobs.

FMSs can be analyzed using queuing network models for performance evaluation

and optimization for system design and planning, one was developed by Chatterjee in 1984.

In his model, a work piece goes through a series of operations at various work centers

before it is unloaded from the system. A path for a given work piece is defined as a

sequential set of operations. The flexibility of the system allows for various kinds of parts

to be processed at the same time. The work center may consist of a single machine capable

of performing a single job or multiple jobs (i.e., multi-tool machine with automated tool

changing capabilities) or a group of machines. Hence, a work piece which enters the

system has the option of going to several different workstations. This is governed by

the type of operation required on a job and gives rise to at least one path which the job

may follow before being unloaded. Therefore, the network of work centers and the

transportation system (connecting work centers and the load/unload center) allows many

possible paths for a work piece to move through the system. It has been found that

variety and fluctuations in the demand of various work pieces or parts being routed

influence the nature of the FMS routing procedure.

The pioneering work in the area of analytical modeling of FMS was done by Solberg in

1978, with the development of the CAN-Q model based on a closed queuing network.


50

Each of the FMS models has vast variety of the modeling formulation details, but here

in this experiment our main focus is on the bottle -neck model (Deterministic model),

we will not go in depth of the other models.

DISCRETE EVENT SIMULATION:

In the letter stages of design, discrete event simulation probably offers the most

accurate method for modeling the specific aspects of the given FMS. The computer

model can be constructed to closely resemble the details of a complex FMS operation.

Characteristics such layout configuration, number of pallets in the system, and

production scheduling rules can be incorporated into the FMS simulation model.

Indeed, the simulation can be helpful in determining optimum values for these

parameters.

A discrete-event simulation based on a discrete-state model fires the event with the

earliest scheduled time among all scheduled events enabled in the current state. As a

result, the current state may change, in turn causing some formerly enabled events to

become disabled, and some disabled ones to become enabled. The process starts with the

initial state, which is normally an input specified by the model itself, and, along the way, it

accumulates state-dependent measures, or rewards, which in turn are used to compute

statistics such as means and variances. The simulation ends according to various

criteria, such as maximum number of events or runtime reached, or desired precision of

some measures met. While the system model can have an enormous or even infinite state

space, only a finite but large subset of states is of course explored on any finite run (with

some states likely to be visited multiple times). Analogously, the number of possible state-

to-state transitions is also large. In practice, this makes it impossible to use a low-level

formalism (i.e., one where all states and transitions are explicitly enumerated). For this

reason, high-level formalisms, i.e., those where a global state is described as a vector of local

(sub)states, such that events affect some of these components, are quite popular.

Examples include Petri nets and queuing models: while their description is compact,

they can define complex underlying low-level stochastic processes. A standard simulation

engine can then interact with such a high-level model just as with a low-level model,

provided we specify a well-defined interface that maps such a structured model onto the

underlying flat view of the low-level process. Since the underlying state space of the

modeled system is still the same, though, the runtime remains large; in fact, it is made even


51

worse by the additional overhead introduced by a high-level model.

OTHER TECHNIQUES:

The other techniques that have been applied to analyze FMS design and operational

problems include mathematical programming and various heuristic approaches.

BOTTLENECK MODEL:

Important aspects of FMS performance can be mathematically described by a

deterministic model called the bottleneck model, developed by Solberg.

Notwithstanding the limitations of a deterministic approach, the value of the

bottleneck model is that it is simple and intuitive. It can be used to provide starting

estimates of FMS design parameters such as production rate and number of

workstations. The term bottleneck refers to the fact that the output of the production

system has an upper limit, given that the product mix flowing through the system is

fixed.

The model can be applied to any production system that possesses this

bottleneck feature, for an instance, a manually operated machine cell or a production

job shop. It is not limited to FMSs.

TERMINOLOGY AND SYMBOLS FOR BOTTLENECK:-

First we should go through the features, terms, and symbols for the bottleneck

model as they might be applied to an FMS:

Part Mix:

The mix of various part or product styles produced by the system is defined by p j =

the fraction of the total system output that is of style j. The subscript

j=1,2,3,4,………,P, where P = the total number of different part styles made in the FMS

during the time period of interest. The values of p j must sum to unity: that is,

1

1.0n

j

i

P

Workstations and Servers:

The flexible production system has a number of distinctly different workstations n.

In the terminology of the bottleneck model, each workstation may have more than one


52

server, which simply means that it is possible to have two or more machines capable of

performing the same operations. Using the terms ―stations‖, and ―servers‖ in the bottleneck

model is a precise way of distinguishing between machines that accomplish identical

operations from those that accomplish different operations. Let si = the number of servers at

workstations i, where

i=1,2,…….,n. We include the load/unload station as one of the stations in the FMS.

Process Routing:

For each part or product, the process routing defines the sequence of operations, the

workstations at which they are performed, ant the associated processing times. The sequence

includes the loading operations at beginning of processing on the FMS and the unloading

operation at the end of the processing. Let

tijk = processing time, which is the total time that a production unit occupies a given

workstation server, not counting any waiting time at the station. In the notation for tijk, the

subscript i refers to a station, j refers to the part product, and k refers to the sequence of

operations in the process routing. For example, the fourth operation in the process plan for

A is performed on machine 2 and taken 8.5 min; thus, t2A4 = 8.5 min. Note that process

plan j is unique to part j. The bottleneck model does not conveniently allow for alternative

process plans for the same part.

Work Handling System:

The material handling system used to transport part or products within the FMS can

be considered to be a special case of workstations. And it is designated as station n + 1, and

the number of carriers in the system like convey or charts, AGVs, monorail vehicles, etc, is

analogous to the umber of servers in a regular workstation. Let sn+1 = the number of

carriers in the FMS handling system.

Transport Time:

Let tn+1 = the mean transport time required to move a part from one workstation to

the next station in the processing route. This value could be computed for each individual

transport based on transport velocity and distances between stations in the FMS, but it more

convenient to simply use an average transport time for all moves in the FMS.


53

Operation Frequency:

The operation frequency is defined as the expected number of times a given

operation in the process routing is performed for each work unit. For example, an inspection

might be performed on a sampling basis, once every four units: hence, the frequency for this

operation would be 0.25. In other cases, the part may have an operation frequency greater

than 1.0; for example, for a calibration procedure that may have to be performed more than

once on average to be completely effective. Let

f ijk = the operation frequency for operation k in process plan j at station i.

FMS Operational Parameters:

Using the above terms, one can text define certain average operational parameters of

the production systems. The average work load for a given station is defined as the mean

total time spent at the station per part. It is calculated as follows:

i ijk ijk i

j k

WL t f p

Where WLi = average workload for station i (min), tijk = processing time for operation k in

process plan j at station I (min), f ijk = operation frequency for operation k in part j at

station I; and p j = part mix fraction for part j.

The work holding system (station n + 1) is a special case as noted in the terminology.

The worl load of the handling system is the mean transport time multiplied by the average

number of transports required to complete the processing of a workpart. The average

number of transports is equal to the mean number of operations in the process routing

minus one. That is,

1.t ijk j

i j k

n f p

Where, nt = mean number of transports.

System Performance Measures:

Important measures for assessing the performance of an FMS include production

rate of all parts, production rate of each part style, utilizations of the different workstations,

and number of busy servers at each workstation. These measures can be calculated under the


54

assumption that the FMS is producing at its maximum possible rate. This rate is constrained

by the bottleneck station in the system, which is the station with the highest workload per

server.

The workload per server is simply the ratio for each station. Thus

the bottleneck is identified by finding the maximum value of the ratio among all stations.

The comparison must include the handling system, since it might be the bottleneck in the

station.

Let WL*, s*, and t* equal the workload, number of servers, and processing time,

respectively, for the bottleneck station. The FMS maximum production rate of all parts can

be determined as the ratio of s* to WL*. One should always refer to it as the maximum

production rate because it is limited by the capacity of the bottleneck station.

*

*

* Sp

WLR

Where R*p = maximum production rate of all part styles produced by the system,

which is determined by the capacity of the bottleneck station (pc/min), s* = number of

servers at the bottleneck station, and WL* = workload at the bottleneck station (min/pc).

The value of the R*p includes parts of all styles produced in the system. Individual

part production rates,can be determined by multiplying R*p by the respective part mix ratios.

That is,

*

*

* * Spj pj j WL

R P R P

Where R*pj = maximum production rate of part style j (pc/min).

The mean utilization of each workstation is the proportion of time that the servers at

the stations are working and not idle. This can be computed as follows.

Where Ui = utilization of station i. The utilization of the bottleneck station is

100% at R*p .

To obtain the average station utilization, one simply computes the average value of

i

i

WL

S


55

all stations, including the transport system. This can be calculated as follows:

1

1

n

i i

i

s u

nU

Where U is an unweighted average of the workstation utilizations.

A more useful measure of overall FMS utilization can be obtained using a weighted average,

where the weighting is based on the number of servers at each station for the n regular

systems, and the transport system is omitted from the system.

The overall FMS utilization is calculated as follows:

Where Us = overall FMS utilization, Si = number of servers at station i.

1

1

n

i i

i

n

i

i

s u

s

Us

Finally, the number of busy server at each station is of interest. All of the servers at

the bottleneck station are busy at the maximum production rate, but the servers at the other

stations are idle some of the time. The values can be calculated as follows:

* ipi i

i

WLBS WL R

S

Where BSi = number of busy servers on average station I, and WLi = Workload t

station i.

Bottleneck model on a simple problem:

A flexible machining system consists of two machining workstations and a

load/unload station. Station-2 performs milling operations and consists of two servers.

Station-3 has one server that performs drilling. The stations are connected by a plant

handling system that has four work carriers. The mean transport time is 3.0 min. The FMS

produces two parts are presented in the table. The operation frequency is 1.0 for all

operations. Determine: a) maximum production rate of the FMS, b) corresponding


56

production rates of each product c) utilization of each station, and d) number of busy servers

at each stations.

SOLUTION:

a) To compute the FMS production rate, we first need to compute workloads at

each station, so that bottleneck station can be identified.

WL1 = (4 + 2) (0.4) (1.0) + (4 + 2) (0.6) (1.0) = 6.0 min.

WL2 = 30 (0.4) (1.0) + 40 (0.6) (1.0) = 36.0 min.

WL3 = 10 (0.4) (1.0) + 15 (0.6) (1.0) = 13.0 min.

The station routing for both parts is the same: 1 → 2→ 3→ 1. There are three moves, nt =

3.

WL4 = 3 (3.0) (0.4) (1.0) + 3 (3.0) (0.6) (1.0) = 9.0 min.

The bottleneck station is identified by finding the largest WLi / Si ratio.

For station-1, WL1 / S1 = 6.0 / 1.0 = 6.0 min.



For station-4, the part handling system, WL4 / S4 = 9.0 / 4 = 2.25 min.


57

The maximum ratio occurs at station-2, so it is the bottleneck station that determines the

maximum production rate of all parts made by the system.

= 2/ 36.0 = 0.05555 pc/ min = 3.333 pc/ hour.

b)To determine production rate of each product, multiply R*p by its respective part mix

fraction.

= 3.333 (0.4) = 1.333 pc / hour.

= 3.333 (0.6) = 2.00 pc/ hour.

c)The utilization of each station:

U1 = WL1 = (6.0/ 1) (0.05555) = 0.333 (33.3%)

U2 = (36.0\ 2) (0.05555) = 1.0 (100%)

U3 = (13.0/ 1) (0.05555) = 0.7222 (72.2%)

U4 = (9.0/ 4) (0.05555) = 0.125 (12.5%)

d)Mean number of busy servers at each station:

BS1 = WL1 = 6.0 (0.05555) = 0.333.

BS2 = WL2 = 36.0 (0.05555) = 2.0.

BS3 = 13.0 (0.05555) = 0.722.

BS4 = 9.0 (0.05555) = 0.50.

Extended Bottleneck Model:

Some assumptions of the bottleneck models are

Sufficient number of parts in the system to avoid starving of workstations

*RP

*

aRP

*

bRP

*

6

RP

*RP

*RP


58

There is no delay due to queues

Extended bottleneck approach can overcome some of the assumptions

Assumes a closed queuing network with fixed number of parts in the FMS

When one part is completed and exits the FMS, a new raw workpart

Immediately enters the system

Let N be the number of parts in the system

N plays a critical role in the operation of the system

If N is smaller than the number of workstations, then some of the stations will be idle

Due to starving – even the bottleneck station

If N is large, then the system will be fully loaded with queues of parts waiting in front of

stations.

R*p will provide good estimation of the production capacity.

Long manufacturing lead time.

As per Little's law

WIP = Throughput Manufacturing Lead Time (MLT)

NR p (MLT)

1

1

n

i n w

i

MLT wl wl T

Tw - Mean waiting time experienced by a part due to queues at the stations

Based on the value of N(small or high) and Little‘s law, the system parameters (production

rate and MLT ) can be calculated.


59

Case 1 (small N):

Bottleneck station is not fully utilized.

Production rate is not R*p

Tw of a unit is theoretically zero.

The MLT can be calculated and the production rate can be calculated using Little‘s law.

1 1

1

n

i n

i

MLT wl wl

MLT1 - MLT for case 1.

1

Np MLT

R

Rpj = pj Rp

Case 2 (Large N):

• Production rate is constrained by bottleneck station.

*

*

* Sp

WLR

MLT can be calculated using Little‘s law

2 *

NMLT

RP

2 1

1

n

w i n

i

T MLT WL WL

The dividing line between case 1 and case 2 is depending on the critical value of N

Let N* be the critical value of N

* * *

1 1

1

( )n

i n

i

N RP WL WL RP MLT


60

Graphical Representation of extended bottleneck model:

Fig. General behavior of the extended bottleneck model

(a) MLT as a function of N and (b) Production rate as a function of N.

Validity of the model:

The author (Mejabi) of the model compared the result with the result obtained from

Queuing model (Can-Q) for several thousand problems

An adequacy factor is suggested which describe the discrepancies of this model from

queuing model

Adequacy factor (AF)

1

/( )n

i

i

AF N U S

Anticipated discrepancies between the extended bottleneck model and CAN-Q model as a

function of the adequacy factor.

Adequacy Factor Anticipated discrepancies with Can-Q


61

AF < 0.9 Discrepancies < 5% are likely.

0.9 < AF < 1.5 Discrepancies > 5% are likely.

AF > 1.5 Discrepancies < 5% are likely.

Sizing of FMS:

Determination of number of servers required at each workstation to achieve a specified

production rate

Information needed

Part mix, process routing and processing times

Si = Minimum integer > Rp ( WLi )

Si - Number of servers at station i

Rp- Specified production rate of all parts to be produced by the system

WLi- Workload at station i.


62

AIM: TO STUDY GROUP TECHNOLOGY AND STRUCTURE OF CODING

SYSTEM.

INTRODUCTION :

Group technology is a manufacturing philosophy in which similar parts are identified

and grouped together to take advantage of their similarities in manufacturing and design.

Similar parts are arranged into part families. For example, a plant producing 10,000 different

part numbers may be able to group the vast majority of this part into 50 or 60 distinct

families. Each family would possess similar design and manufacturing characteristics. Hence,

the processing of each member of a given family would be similar, and this results in

manufacturing efficiencies. These efficiencies are achieved in the form of reduced setup

times, lower in-process inventories, better scheduling, improved tool control, and the use of

standardized process plans. In some plants where GT has been implemented, the production

equipment is arranged into machine groups or cells in order to facilitate work flow and parts

handling.

In product design, there are also advantages obtained by grouping parts into families.

For example, a design engineer faced wit the task of developing a new part design must

either start from scratch or pull an existing drawing from the files and make the necessary

changes to conform to the requirements of the new part. The problem is that finding a

similar design may be quite difficult and time consuming. For a large engineering department,

there may be thousands of drawings in the files with no systematic way to locate the desired

drawing. As a consequence, the designer may decide that it is easier to start from scratch in

developing the new part. This decision is replicated many times over in the company. Thus

consuming valuable time creating duplicate or near-duplicate part designs. If an effective

design retrieval system were available, this waste could be avoided by permitting the engineer

to determine quickly if a similar part already exists. A simple change in an existing design

would be much less time consuming that starting from scratch. This design-retrieval system

GANPAT UNIVERSITY



COMPUTER INTEGRATED M

M. T .


ECH CAD- CAM



63

is a manifestation of the group technology principle applied to the design function. To

implement such a system, some form of parts classification and coding is required.

DEFINATION OF GROUP TECHNOLOGY :

Group Technology or GT is a manufacturing philosophy in which the parts having

similarities (Geometry, manufacturing process and/or function) are grouped together to

achieve higher level of integration between the design and manufacturing functions of a firm.

REASONS FOR ADOPTING GROUP TECHNOLOGY :

To shorten manufacturing lead times. By reducing setup, work part handling,

waiting times and batch sizes.

To reduce work-in-progress inventory. Smaller batch sizes and shorter lead times

reduce work-in-process.

To improve quality. This is accomplished by allowing each cell to specialize in

producing a smaller number of different parts. This reduces process variations

To simplify production scheduling. The similarity among parts in the family

reduces the complexity of production scheduling. Instead of scheduling parts

through a sequence of machines in a process-type shop layout, the parts are simply

scheduled through cell.

To reduce setup times. This is accomplished by using group tooling that have been

designed to process the part family, rather than part tooling, which is designed for an

individual part. This reduces the number of individual tools required as well as the

time to change tooling between parts.

PART FAMILIES

A part family is a collection of parts which are similar either because of geometric

shape and size or because similar processing steps are required in their manufacture. The

parts within a family are different, but their similarities are close enough to merit their

identification as members of the part family. The two parts shown in fig are similar from a

design viewpoint but quite


64

different in terms of manufacturing. The parts shown in fig 2 might constitute apart family in

manufacturing, but their geometry characteristics do not permit them to be grouped as a

design part family.

EXAMPLE ON PART FAMILY FORMATION

The examples are on the basis of the design part family, and manufacturing part family.

1. Design part family.

As shown in the fig there are two parts which are differing in are and other geometry

but they require drilling operation of different size so, it is included in the design part

family.


65

2. Manufacturing part family.

As shown in fig there are two parts different in the geometric aspect but both the

parts require the same operation of drlling +0.5mm. Though the parts have different

geometry they have same manufacturing characteristics. This is called as the

manufacturing part family.

CODING SYSTEM STRUCTURE

A part coding scheme consist of a sequence of symbol s that identify the parts design

and/or manufacturing attributes. The symbol in the code can be al numaric, all alphabetic,

or a combination of both types. However, most of the common classification and coding

systems use number digit only. There are three basic code structure used in group

technology application:

1. Hierarchical structure

2. Chain type structure

3. Hybrid structure, a combination of 1 & 2.

1. Hierarchical structure

A hierarchical structure is also called a monocode. In a monocode each number

is qualified by the preceding character. With the hierarchical structure, the interpretation

of each succeeding symbol depends on the value of the preceding symbols. Other names

commonly used for this structure are monocode and tree structure. The hierarchical code

provides a relatively compact structure which conveys much information about the part

in a limited number of digits. One advantage of system is that it can represent a large

amount of information in very few code positions. A drawback is the potential

complexity of the coding system.


66

2. Chain type structure

A chain structure is called a polycode. In the chain type structure, the

interpretation of each symbol in the sequence is fixed and does not depend on the value

of preceding digits. Another name for this structure is polycode. The problem assosiated

with polycode is that they tend to be relatively long. On the other hand, the use of a

polycode allows for convenient identification of specific parts with similar processing

requirements.

To illustrate the difference between two structure, consider a two-digit code 15

or 25. Suppose that the first digit stands for general part shape. The symbol 1 means

round work part and 2 means flat rectangular geometry. In a hierarchical code structure

the interpretation of second digit would depend on the value of first digit. If preceded by

1, the 5 might indicate some 1/d ratio, and if preceded by 2 the 5 might be interpreted to

specify some overall length. In chain type structure, the symbol 5 would be interpreted

the same way regardless the value of the first digit. For example, it might indicate overall

part length, or wheather the part is rotational or rectangular. The major drawback is that

they can not be as detailed as hierarchical structures with the same number of coding

digits.

3. Hybrid structure

Most of the commercial parts coding systems used in industry are a combination

of two pure structure. The hybrid structure is an attempt to achieve the best feature of

monocodes. Within each of these shorter chains, the digit are independent, but one or

more symbols in the complete code number are used to classify the part population into

groups, as in the hierarchical structure. This hybrid coding seems to best serve the needs

of best serve the needs of both design and production.

GT LAYOUT :

The various machine tools are arranged by function. There is a lathe section, milling

machine section, drill press section, and so on. During the machining of a given part, the

work piece must be moved between sections, with perhaps the same section being visited

several times. This results in a significant amount of material handling, a large in-process

inventory usually more setups than necessary, ling manufacturing lead times, and high cost.

Fig shows a production shop supposedly equivalent capacity, but with the machines arranged

into cells. Each cell is organized to specialize in the manufacture of a particular part family.

Advantages are gained in the form of reduced work piece handling, lower setup times ,less


67

inprocess inventory, less floor space and shorter lead times. Some of the manufacturing cells

can be designed to form production flow lines, with conveyors used to transport work parts

between machines in the cell.

PART CLASSIFICATION AND CODING :

This method of grouping parts into families involves an examination of the

individual design and/or manufacturing attributes of each part. The attributes of the part are

uniquely identified by means of code number. This classification and coding may be carried

out on the entire list of active parts if the firm or a sampling process may be used to establish

the part families. For example, parts produced in the shop during a certain given time period

could be examined to identify part family categories. The trouble with any sampling

procedure so the risk that the sample may be unrepresentative of the entire population.


68

However, this risk may be worth taking, when compared to the relatively enormous task of

coding all the company‘s parts.

Many parts classification and coding systems have been developed throughout the world, and

there are several commercially available packages being sold to industrial concerns. It should

be noted that none of them has been universally adopted. One of the reasons for this is that

a classification and coding system should be custom-engineered for a given company or

industry. One system may be best for one company while a different system is more suited to

another company.

TYPES OF CODING SYSTEM :

Three parts classification and coding systems which are widely recognized among people

familiar with GT:

1. Optiz system

2. MICLASS system

3. CODE system

The Optiz Classification System


69

This part classification and coding system was developed by H. Optiz of the

University of Aachen in West Germany. It represents one of the pioneering efforts in the

group technology are and is perhaps the best known of the classification and coding schemes

The optiz coding system uses the following digit sequence

12345 6789 ABCD

The basic consists of nine digits, which can be extended by adding four more digits.

The first none digits intended to convey both design and manufacturing data. The general

interpretation of the nine digits is indicated in Fig. The first five digits. 12345 are called the

―form code‖ and describe the primary design attributes of the part. The next four digits,

6789, constitute the ―supplementary code‖ It indicates some of the attributes that would be

of use to manufacturing. The extra four digits, ABCD are referred to as the ―secondary

code‖ and are intended to identify the production operation type and sequence. The

secondary code can be designed by the firm to serve its own particular needs.


70

MICLASS System

MICLASS stands for metal institute classification system and was developed by TNO,

the Netherlands Organization of Applied Scientific Research. It was started in Europe about

five years before being introduced in US in 1974. The MICLASS system was developed to

help automate and standardize a number of design, production and management functions.

These include

Standardization of engineering drawings

Retrieval of drawing according to classification number

Standardization of process routing

Automated process planning

Selection of parts for processing on particular groups of machine tools

Machine tool investment analysis

The MICLASS classification number can range form 12 -30 digits. The first 12 digits

are a universal cod that can be applied to any part. Up to 18 additional digits can be used to

code data that are specific to the particular company or industry. For example lot size, piece

time, cost data, and operation sequence might be include in the 18 supplementary digits.

The workpart attributes coded in the first 12 digits of the MICLASS number are as follows

as in table given

One of the unique features of the MICLASS system is that parts can be cooled using

a computer interactively. To classify given part design, the user responds to a series of

questions asked by the computer. The number of questions depends to a the complexity of

part. For a simple part, as few as seven questions are needed to classify the part. For and

average part, the number of questions ranges between 10-20. On the basis of responses to its

questions, the computer assigns a code number to the part.

The CODE System

The CODE system is a parts classification and coding system developed and

marketed by Manufacturing Data Systems, Inc of Ann Arbor Michigan. Its most universal

application is in design engineering for retrieval of part design data, but it also has

applications in manufacturing process planning, purchasing, tool design, and inventory

control.


71

The CODE number has eight digits. For each digit there are 16 possible values

which are used to describe the parts design and manufacturing characteristics. The initial

digit position indicates the basic geometry of the part and is called the major division of the

CODE system. This digit would be used to specify whether the shape was a cylinder, flat

piece block, or other. The interpretation of the remaining seven digits depends on the value

of first digit, but these remaining digits form chain-type structure. Hence the CODE system

posses a hybrid structure.

The second and third digits provide additional information concerning the basic

geometry and principal manufacturing processes such as threads, grooves, slots and so forth.

Digits 7 and 8 are used to indicate the overall size of the part by classifying it into one of the

16 size ranges for each of two dimensions. Fig shows a portion of the definitions for digits.

BENEFITS OF GROUP TECHNOLOGY :

Product design

Tooling and setups

Material handling

Production and inventory control

Employee satisfaction

Process planning procedures

Product design benefits

In the area of production design, improvement and benefits are derived from the use

of a parts classification and coding system, together with a computerized design-retrieval

system. When a new part design is required, the engineer or draftsman can devote a few

minutes to figure the code of the required part. Then the existing part designs that match the

code can be retrieved to see if one of the will serve the function desired. The few minutes

spent searching the design file with the aid of the coding system may save several hours of

the designer‘s time. IF the exact part design cannot be found, perhaps a small alteration of

the existing design will satisfy the function. Use of the automated design-retrieval system

helps to eliminate design duplication and proliferation of new parts designs.

Other benefits of GT in design are that it improves cost estimating procedures and

helps to promote design standardization. Design features such as inside corner radii, chamfer

and tolerances are more likely to become standardized with GT.


72

Tooling and Setups

GT also tends to promote standardization of several areas of manufacturing. Two of

these areas are tooling and setups.

In tooling, an effort is made to design group jigs and fixtures that will accommodate

every member of a parts family. Work holding devices are designed to use special adapters

which convert the general into one that can accept each part family member.

The machine tools in a GT cell do not require drastic changeovers in setup because

of the similarity in the work parts processed on them. Hence, setup time is saved, and it

becomes more feasible to try to process parts in an order so as to achieve a bare minimum of

setup changeovers. It has been estimated that the use of GT can result in 69% reduction in

setup time.

Material Handling

Another advantage in manufacturing is reduction in the work part move and waiting

time. The group technology machine layouts lend themselves to efficient flow of material

through the shop. The contrast is sharpest when the flow line cell design is compared to the

conventional process type layout.

Production and Inventory Control

Several benefits accrue to a company‘s production and inventory control function as

a consequence of GT.

Production scheduling is simplified with GT. In effect, grouping of machines into

cells reduces the number of production centers that must be scheduled. Grouping of parts

into families reduces the complexity and size of the parts scheduling problem. And for those

work parts that cannot be processed through any of the machine cells, more attention can be

devoted to the control of these parts. Because of the reduced setups and more efficient

materials handling with machine cells, production lead times, work-in process and late

deliveries‘ can be reduced. Estimates on what can be expected are provided by DeVries

70% reduction in production times

62% reduction in work-in-process inventories

82% reduction in overdue orders.


73

Employee Satisfaction

The machine cell often allows parts to be processed from raw material to finished

sate by small group workers. The workers are able to visualize their contributions to the firm

more clearly. This tends cultivate an improved worker attitude and higher level of job

satisfaction,

Another employee-related benefits of GT is that more attention tends to be given to

product quality. Workpart quality is more easily traced to a particular machine cell in GT.

Consequently, workers are more responsible for the quality of work they accomplish.

Traceability of part defects is sometimes very difficult in a conventional process-type layout,

and quality control suffers as a result.

Process Planning Procedures

The time and cost of the process planning function can be reduced throught

standardization associated with group technology. A new part design is identified by its cose

number as belonging to a certain parts family, for which into computer software to form a

computer-automated process planning system.


74

AIM: ANALYSIS OF MATERIAL HANDLING AND STORAGE SYSTEM.

INTRODUCTION:

Manual Material handling operation are carried out in most industrial plant. Each

handling task posses unique demand on the worker. However workplaces can help the

workers to perform these task safely and easily by implanting and upholding proper policies

and procedure.

Joints 1. 1.Ankle 2. 2.knee 3. 3.Hip 4. 4.Shoulder 5. 5.Elbow

Segments

a. a. shank b. b. thigh c. c .Trunk d. d. Upper arm e. e.forearm

c d e b

GANPAT UNIVERSITY




M. T .

EXPERIMENT NO: 5

1

2

3

4

5

DATE: ..../..../........

ECH CAD- CAM



75

For last several decades, manual material handling has attracted great interest from

researchers in many disciplines, primary because of the huge amount of work and finances

losses and human sufferings caused by low back pain and injuries.

In the last several year material handling has become rapidly evolving science.

For moving material in and out in warehouse many type of equipment and system are in

used, depend on type of material and volume handle.

In warehouse, material handling operation are performed by following stage.

Unloading the incoming material from transport vehicle

Moving unloading material to assign storage section in warehouse

Lifting storage material from storage place during its storage packing.

Moving the material for inspection and packing

Loading packages on transporting vehical.

Design of Material Handling is depend on

Volumes to be handled

Speed in handling

Productivity

Product characteristics ( weight,size,shape etc)

Nature of the product

TYPES MATERIAL HANDLING SYSTEM

1. Lifting and Transport System: It is used to move product around the

production facility, from loading bay to storage, from storage to production,

around production, from production to storage, and from storage to loading

bay. The equipment that falls into this category are fork lift, trucks, order

picking truck, over hade cranes, tower crane and belt, chain and overhead crane.

2. Storage Equipment : It is used store materials, components, and assemblies.

The level of complexity of this type of equipment is wide ranging, from welded

cantilever steel rack to hold lengths of stock materials to a powered vertical


76

carousel system. Also within this category are pallet racks, mobile self units, and

plastic, wood and steel container.

3. Automated Handling Equipment : Manufacturings of automated handling

equipment produce automate guided vehicles, storage and retrieval equipment,

conveying systems and product sortation equipment. The level of automation

varies depending on the handling requirements. Fully automated handling

systems ensure that the materials are deliver to production l ine when required

without significant manual intervention.

4. Automated Guided Vehicles ( AGVs ) : an agv is a material handling device

that is used to move part between machines and workcenter. They are small ,

independently powered vehicle, those are usually guided by cables that are

buried in the floor or they use an optical guidance system. They are controlled

by receiving instruction either from central computer or from their own board-

computer.

5. Robotics : in manufacturing application, robot can be used for assembly

work ,process such as painting ,welding and for material handling. More resent

robots are equipped with sensory feedback through vision. The main advantage

of robots is, they can be used for repetitive ,monotonous task that need

precision. They can be used in hazardous environment that are not suitable for

human operator.

Automated guided vehicles (AGV) are vehicles that are equip with automated

guidance

Systems and are capable of following prescribed paths. Unlike traditional robots. AGV a re

not manipulators, they are driverless vehicle that are programmed to guide path. In

automated factories and facilities AGV move pallets and container.

The main benefit of AGV is that they reduce labor costs. But in material handling

facilities there is another benefit. Material handling handling has always been dangerous.

Injuries occure due to lake of driver attention. Obstacle detection is therefore a key to

allowing AGVs to interact with personnel not paying attention. Obstacle detection is

therefore a key to allowing AGVs to interact with personnel safely while optimizing vehicle

speed.


77

TYPES OF AGVS:

Automated guided vehicle system consists of the computer,software and technology that

are the brains behind the AGV. Without computer software systems and communications

networks, only the simplest AGV functions can be performed

Camera guided AGVs are used when precise guidance accuracy is needed,such as in

crowded environments and smaller sized facilities. An on board camera focuses and guides

the AGV while performing.

Forked AGVs are used to pick up and deliver various loads, such as pallets, carts, rolls and

others. There can be manually driven as well as used automatically, and have the ability to lift

loads to many levels.

Inertial guided AGVs use a magnet sensing device, a gyroscope that measures the units

heading and a wheel odometer that calculates the distance traveled. Magnets mounted

beneath the floor are detected by the on board magnetic sensing device and combine with

the first two readings to give an accurate positional location.

Large chassis/unit load AGVs are used to transport heavier loads with various transfer

devices such as roller beds,lift/lower mechanisms and custom mechanisms.

Laser guided AGVs use mounted laser scanners that emit a laser and reflect back from

target. The vehicle s location can be determined based on distance to the target and time of

reflection information.

Optical guided AGVs use a latex-based photosensitive tape on a facilitys floor for

guidance.Distance is measured by use of wheel odometers,which establish stop locations for

the AGV along the course.


78

Outrigger AGVs have horizontal stabilizing legs to provide lateral support, and are used to

handle pallets ,rolls and racks.

Small chassis AGVs are able to maneuver through crowded workplaces through laser

sensing, while transporting smaller load.

Small vehicle AGVs are capable of determining their own traffic and routing without

necessitating a central controller.

Tug/tow AGVs are used to pull trailers are usually manned by an operator who adds and

remove trailers at designated stops. These can follow a basic loop or more complicated path.

Wire guided AGVs uses charged wire that is buried beneath the floor for proper guidance

and has small antenna composed of metal coils mounted on their bottoms. The stronger the

field between the buried wire and antennae, the higher the voltage induced to the coil.

Unit load carries : Low built vehicle 3 type

Unit handler, which can be fitted with type of load handler on top, Roller or chain

conveyor,fixed load table, lifting load table or arms, telescopic fork,etc.

Load capacity up to 12000 lbs.

There are five wheel version.

Single or fully by directional.

Ideal for material delivery and manufacturing.

ANALYSIS OF AGV SYSTEMS

The analysis of AGV systems is used to determine

1. The number of AGV required

2. Cycle time.

3. handling system efficiency.

It is assumed that the vehicle operates at a constant speed of V. The acceleration and

other effects that influence the speed are ignored.


79

The time for typical delivery cycle in operation of the vehicle includes

Loading at the pick up station.

Unloading at the drop of stations.

Travel time to the drop off station.

Empty travel time of the vehicle between deliveries

Therefore the total cycle time per delivery per vehicle is given by

Tv = Tl + Tu + Ld/v +Le/v

Where, Tv = Delivery cycle time (min/delivery)

Tl = pick up time (min.)

Tu = Drop off time (time.)]

Th=Tl + Tu = Handling time (min.)

Ld = Distance the vehicle travels between load and unload station (m)

Automated Material Movement and Storage system

Le = Distance the vehicle travels empty until the start of next delivery cycle (m)

V = velocity ( m/min).

The delivery cycle time can be used to determine the rate of deliveries per vehicle and

number of vehicles required.

The hourly rate of deliveryies per vehicle is 60 minutes divided by delivery cycle time

Tv, With adjusting for any time losses during the hour.

The possible time losses include availability, traffic congestion and efficiency of

manual drivers.

So traffic factor accounts and lies between .0.85 and 1

So number of deliveries per hour per vehicle = 60 Ft/Tv or

Number of deliveries per hours per vehicle = (60 Eh) / (Ld/v)


80

Where Eh = handling system efficiency

= { ( Ld/v) x Ft} / (Ld/v + Th +Le/v)

so number of AGVS required = Number of deliveries required per hour

` Number of deliveries/hour/vehicle

Example

Following are the data for AGV system.

Vehicle velocity = 45m/min.

Average distance traveled/ delivery= 135m

Pick up time = 45 sec.

Drop off time = 45 sec.

Average distance traveling empty = 90m

Traffic factor = 0.9

Determine the number of vehicles required to satisfy the delivery demand if the delivery

demand is 40 deliveries per hour. Also determine the handling system efficiency.

Solution: Ld = 135m, Le =90m ,Tl = 45 sec = 0.75 min,

Th = Tl + Tu

= 0.75 + 0.75

= 1.5 min.

v = 45 m/min. & Ft= 0.9

Total cycle time per delivery per vehicle is given by

Tv = Th + Ld/v + Le/v

= 0.75 + 0.75 + 135/45 + 90/45

= 6.45 min.

The number of delivery per hour per vehicle = 60 Ft/Tv

= 60 x 0.9/6.45

= 8.37 deliveries/hour/vehicle.

Number of vehicles required = Number of deliveries required per hour

Number of deliveries/ hour/ vehicle

= 40/8.37


81

= 4.82

= 5

Handling system efficiency = {(Ld/v)xFt}/{(Ld/v) +PTh+ (Le/v)}

= { (135/45) x 0.9 }/ {(135/45) = 1.5 + (90/45)}

= 0.4154

= 41.54 %

AUTOMATED STORAGE AND RETRIEVAL SYSTEMS (ASRS):

Automated storage and retrieval systems (ASRS) are means to

high density, hands free buffering of materials in distribution and manufacturing

environments. There are several classes of automated storage and retrieval (ASRS) that are

characterized by weight and size handling characterized by weight and size handling

characteristics.

Unit load ASRS

Mini Load ASRS

Carousel ASRS

Unit Load ASRS

Unit Load ASRS machines are generally pallet handling

systems with capacities that vary much like lift trucks. Unit load ASRS systems are often

quit tall and sometimes support the building shell that contains them. The density, security

and labour/machinery savings they provide, make them a good choice in a variety of

application from cold storage to general warehousing.

Mini load ASRS

Mini load ASRS, operating on same principles as the Unit

loads this unit load machine handle smaller and lighter loads. These typically range from

metal trays and totes to shipping cartons. Mini loads may be used in traditional stockroom


82

applications but are also well suited as buffers to support manufacturing processes and

shipping systems.

Carousel ASRS

Carousel ASRS, the industrial carousel may be integrated with a specific purpose robotic

inserter/ extractor for small load buffering. Very often, carousel ASRS is applied in lights –

out stockroom. This technology finds itself at the heart of systems varying widely in

application from the food industry to the manufacturing floor.

ADVANCED AUTOMATED STORAGE AND RETRIEVAL SYSTEM:

Stores and retrieves production parts for aging, testing, or optimization flow.

Allows parts to be grouped into multiple batches; internal database handles all part

information including time stamp for accurate retrieval by age.

Storage and Retrieval (SR) System combined high- density storage of components,

work-in-process storage or finished goods with automated storage, retrieval and handling.

In addition to complete line of conveyers, transfers and ergonomic devices, Industrial

Kinetics, Inc. manufacture and integrates a wide variety of storage and Retrieval machines.

Our innovative equipment can interface with carousels, live or static rack installations, and

custom configured work cells, Industrial Kinetics, inc. provided systems include the most

current inventory control technology.

ANALYSIS OF ASRS:

The analysis OF ASRS is used in order to determine the transaction cycle time.

The transaction cycle involves retrieval of load out of storage or delivery of a load out of

storage or delivery of a load in to the storage or both of the activities in the single cycle.

The two type of transaction cycle are:

1. Single command cycle: It involves either retrieving a load from the storage or

entering a load into the storage but not both in a single cycle.


83

2. Dual command cycle : It involves both entering a load into storage and retrieval of

the load from storage in the same cycle. It represents the most efficient way to operate the ASRS since two loads are handled in a single transaction.

In order to compute the transaction cycle time based on the formulas derived by Bozer

and Whit following assumptions have to be made.

Randomized storage of loads in ASRS

Storage compartments are of same size.

Pick up and delivery station is located at base and end of the aisle

Horizontal and vertical speed of the storage/ retrieval machine are constant

Simultaneous horizontal and vertical travel

For single command cycle, the transaction time is given by,

Tsc = T(Q2 /3 + 1) +2 Tpd

For dual command cycle , the transaction time is given by,

Tds = T ( 4/3 + 0.5 Q2-Q3/30) +4Tpd

Where, Ls = Length of aisle

Hs = Height of aisle

Vh = Average horizontal speed of SR machine

Tpd = shuttle time to perform pickup and deposit.

The time required for horizontal and vertical travel in full length of the storage system are

given by

Th = Ls / Vh and

Tv = Hs / Vv

Using these travel times, the following parameters are defined,

T = max (th,tv)


84

Q min = min (th/T, tv/T)

QUANTITATIVE ANALYSIS:

The size and capacity of a storage carousel can be determined with reference to the given fig.

The individual bins are hung on carriers that revolve around the carousel track. The

circumference of the carousel track is given by

C = 2 ( Ls – Ws) + piWs

Consider the spacing between carriers around the track be given by Sc and the number of

carriers be symbolized as nc.

Hence nc, sc = C

If the number of separate bins hung from a carrier is nb, the total number of bins that is

storage compartments on the carousel = nc nb

Assumption made to derive the time to perform a transaction are

Transaction cycle consists of either a storage or retrieval, but not both that is single

command transactions can be performed.

Speed of the carousel is constant.

Random storage is used in the carousel .

Let us consider a retrieval cycle and the storage transaction is performed under the same

assumption of random storage would be equivalent to retrieval transaction.

The average distance that the carousel has to travel to move randomly located bin to the

unload station at the end of the carousel depends on whether the carousel revolves in only

one or both directions.

For the single direction, the average travel distance is given by


85

Lr = 0.5C

And corresponding time complete a retrieval transaction

Tr = (0.5C/Vc) + Th

Where Th – handling time of the picker to remove the item or items from the bin. For the

carousel capable of bi-directional travel, the corresponding average travel distance and

retrieval transaction time are

Lr = 0.25C

Tr = (0.25C/Vc) + Tc


87

AIM: TO STUDY ABOUT NC, CNC, DNC AND VNC MACHINE TOOLS

ALONG WITH ITS SPECIFICATION AND MODERN FEATURES.

COMPUTER NUMERICAL CONTROL:

Computer numerical control is a NC system that utilizes a dedicated, stored program

computer to perform some or all of the basic numerical control functions. Because of the

trend toward downsizing in computers, most of the CNC systems sold today use a

microcomputer based controller unit. Over the years, minicomputers have also been used in

CNC controls.

In CNC, the program is entered once and then stored in the computer memory. Thus unlike

NC, tape reader is used only for the original loading of the part program and data. Compared

to regular NC, CNC offers additional flexibility and computational capability. New system

options can be incorporated into the CNC controller simply by reprogramming the unit.

Because of this reprogramming capacity, both in terms of part programs and system control

options, CNC is often referred to by the term ―soft-wired‖ NC .

GANPAT UNIVERSITY




M. T .

EXPERIMENT NO: DATE: ..../..../........

ECH CAD- CAM


6


88

FUNCTIONS OF CNC:

There are a number of functions which CNC is designed to perform. Several of these

functions would be either impossible or very difficult to accomplish with conventional NC.

The principal functions of CNC are:

1. Machine tool control

2. In-process compensation

3. Improved programming and operating features

4. Diagnostics

MACHINE TOOL CONTROL:

The primary function of the CNC system is control of the machine tool. This involves

conversion of the part program instructions into machine tool motions through the

computer interface and servo system. The capability to conveniently incorporate a variety of

control features into the soft wired controller unit is the main advantage of CNC. Some of

the control functions, wired circuits than with the computer. This fact has lead to

development of two alternative controller designs in CNC:

1. Hybrid CNC

2. Straight CNC

In the hybrid CNC system, the controller consists of the soft wired plus hard wired

circuits. The hard wired components perform those functions which they do best, such as

feed rate generation and circular interpolation. There are several reasons for the popularity of

the hybrid CNC configuration. As mentioned previously, certain NC functions can be

performed more efficiently with the hard wired circuits. These are functions which are

common to most NC systems. Therefore, the circuits that perform these functions can be

produced in large quantities at relatively low cost. Use of these hard wired circuits saves the

computer from performing these calculation chores. Hence a less expensive computer is

required in the hybrid CNC controller.

The straight CNC system uses a computer to perform all the NC functions. The

only hard wired elements are those required to interface the computer with the machine tool


89

and operator‘s console. Interpolation, tool position feedback, and all the other functions are

performed by computer software. It is possible to make changes in the interpolation

programs, whereas the logic contained in the hard wired circuits of the hybrid CNC cannot

be altered.

IN PROCESS COMPENSATION

A function closely related to machine tool control is in process compensation. This

involves the dynamic correction of the machine tool motions for changes or errors which

occur during processing. Some of the options included within the category of CNC in

process compensation are:

Adjustments for errors sensed by in process inspection probes and gauges.

Recomputation of axis positions when an inspection probe is used to locate a

datum reference on a work parts.

Offset adjustments for tool radius and length.

Adaptive control adjustments to speed and/or feed.

Computation of predicted tool life and selection of alternative tooling when

indicated.

IMPROVED PROGRAMMING AND OPERATING FEATURES

The flexibility of the soft wired control has permitted the introduction of many

convenient programming and operating features. Included among these are the following:

Editing of part programs at the machine. This permits correction or

optimization of the program.

Graphic display of the tool path to verify the tape.

Various types of interpolation circular, parabolic and cubic interpolation.

Use of specially written subroutines.

Local storage of more than one part program.


90

DIAGNOSTICS

NC machine tools are complex and expensive systems. The complexity increases the

risk of components failures which lead to system downtime. It also requires that the

maintenance personnel be trained to a higher level of proficiency in order to make repairs. A

possible function which goes beyond the normal diagnostics capability is for the CNC

systems to contain a certain amount of redundancy of components which are considered

unreliable. When one of these components fails, the diagnostics subsystems would

automatically disconnect the faulty components and activate the redundant component.

Repairs could thus be accomplished without any breaks in normal operations.

ADVANTAGES OF CNC

Computer numerical control possesses a number of inherent advantages over

conventional NC. The following list of benefits will serve also as a summary of our

preceding discussion:

1. The part program tape and tape reader are used only once to enter the

program into computer memory. These results in improved reliability, since

the tape reader is commonly considered the least reliable component of a

conventional NC system.

2. Tape editing at the machine site. The NC tape can be corrected and even

optimized during tape tryout at the site of the machine tool.

3. Metric conversion. CNC can accommodate conversion of tapes prepared in

units of inches into the International system of units.

4. Greater flexibility. One of the more significant advantages of the CNC over

conventional NC is its flexibility. This flexibility provides the opportunity to

introduce new control options with relative ease at low cost. The risk of

obsolescence of the CNC system is thereby reduced.

5. User written programs. One of the possibilities not originally anticipated for

CNC was the generation of specialized programs by the user. These

programs generally take the form of MACRO subroutines stored in the CNC

memory which can be called by the part program to execute frequently used

cutting sequences.


91

6. Total manufacturing system. CNC is more compatible with the use of a

computerized factory wide manufacturing system. One of the stepping stones

toward such a system is the concept of direct numerical control.

VOICE NC PROGRAMMING

Voice programming of NC machines involves vocal communication of the

machining procedure to a voice input NC tape preparation system. VNC allows the

programmer to avoid steps such as writing the program by hand, keypunching or typing, and

manual verification. One of the principal companies specializing in voice input systems is

Threshold Technology, INC, of Delran, New Jersey.

To perform the part programming process with VNC, the operator speaks into a

headband microphone designed to reduce background acoustical noise. Communication of

the programming instructions is in shop language with such terms as ―turn‖, ―thread‖, and

―mill line‖, together with numbers to provide dimensional and coordina te data. Before the

voice input system can be used, it must be ―trained‖ to recognize and accept the individual

programmer‘s voice pattern. This is accomplished by repeating each word of the vocabulary

about five times to provide a reference set which can subsequently be compared to voice

commands given during actual programming. The entire vocabulary for the threshold system

contains about 100 words. Most NC programming jobs can be completed by using about 30

of these vocabulary words.

In talking to the system, the programmer must isolate each word by pausing before

and after the word. The pause must be only one tenth of a second or longer. This allows the

speech recognition system to identify boundaries for the uttered command so that its wave

characteristics can be compared with words in the reference set for that programmer. Typical

word input rates under this restriction are claimed to be about 70 per minute. As the words

are spoken, a CRT terminal in front of the operator verifies each command and prompts the

operator for the next command.


92

DIRECT NUMERICAL CONTROL

It can be defined as a manufacturing system in which a number of machines are

controlled by a computer through direct connections & in real time. The tape reader is

omitted in DNC. The part program is transmitted to the machine tool directly from the

computer memory. One large computer can be used to control more than 100 separate

machines.

COMPONENT OF DNC SYSTEM

It has four basic components.

1. Central computer

2. Bulk memory, which stores the NC part program

3. Telecommunication line

4. Machine tools

Computer calls the part program instruction from bulk storage and sends them to the

individual machine as need arises. It also receives data back from the machines.


93

Satellites are minicomputers, and they serve to take some of the burden off the

central computer. Each satellite controls several machines. Group of part programs inst are

received from the central computer & stored in buffers. Feedback data from the machines

are also stored in the satellite buffer before being collected at central computer.

TYPES OF DNC

1. Behind the tape reader (BTR) system.

Here the computer is linked directly to the regular NC controller unit. Tape

reader is replaced by telecommunication lines to DNC computer. There are 2

temporary storage buffers. One buffer is receiving a block of data; the other is

providing control instructions to the machine tool.

2. Special machine control unit.

NC controller is replaced by special machine control unit. Special MCU

facilitate communication between the machine tool & the computer special machine

MCU configuration achieves a superior balance between accuracy of the

interpolation & fast metal removal rates.


94

FUNCTIONS OF DNC

1. NC without punched tape

Several problems of NC are related to the use of punched tape. There is also

the expense associated with the equipment that produces the punched tape.

2. NC part program storage

Purposes of program storage subsystem structuring are:

a) The Programs must be made available for downloading to the NC machine

tools.

b) The subsystem must allow for new programs to entered, old programs to be

deleted & edited.

c) The DNC software must accomplish the post processing function.

d) The storage subsystem must be structures to perform certain data processing

& management function. The storage for NC programs not frequently used.

3. Data Collection, Processing & Reporting

The transfer of data from the machine tools back to the central computer.

The basic purpose is to monitor production in the factory. Data must be processed

by DNC computer & reports are prepared to provide management with information

necessary for running the plant.

4. Communication

Essential communication links in DNC are between the following:

a) Central computer & machine tools

b) Central computer & NC part programmer terminal

c) Central computer & bulk memory

Optional communication links may also be established between the DNC system

and,

a) Computer aided design (CAD) system

b) Shop floor control system

c) Corporate data processing computer

d) Remote maintenance diagnostics system


95

ADVANTAGE OF DNC

1. Elimination of punched tapes & tape readers.

2. Greater computational capability & flexibility because computation & data processing

function are implemented with software rather than hard wired devices.

3. Convenient storage of NC part programs in computer files.

4. Program stored as CLFILE – part program is stored as cutter path data rather than

post processed programs for specific machine tools. It provides flexibility of

production scheduling.

5. Reporting of shop performance is done easily by DNC system.

6. Establishes the framework for the evolution of the future computer automated

factory.

ADAPTIVE CONTROL MACHINING SYSTEM

Adaptive control denotes a control system that measures certain output process

variables & use these to control speed &/or feed. Nearly all the metal cutting variables that

can be measured have been tried in experimental adaptive control system.

Although NC has signification effect on downtime, it can do relatively little to reduce

the in process time compared to a conventional machine tool. NC guides the sequence of

tool positions or the path of tool during machine, adaptive control determines proper speeds

&/or feeds during machining as a functioning of variations in such factors as material

hardness, depth of cut.

Source of variability in machining where adaptive control can be most

advantageously applied,

a) Variable geometry of cut in the form of changing depth or width of cut.

b) Variable work piece hardness & variable machinability.

c) Variable work piece rigidity.

d) Tool wear.

e) Air gaps during cutting.


96

TYPES OF ADAPTIVE CONTROL MACHINING SYSTEM

1. Adaptive control with optimization (ACO)

Here the performance is optimized accuracy to the given prescribed index of

performance. The index of performance is usually an economic function. It is most

delicate closed loop control system which optimizes the conditions automatically.

The system attempts to maximize the ratio of work material removal rate to

tool wear rate known as index of performance.

IP = MRR/TWR

Where,

IP = Index of performance

MRR = Material removal rate

TWR = Tool wear rate

2. Adaptive control with constrains (ACC)

In this system the machining conditions such as feed rate or/and speed are

maximized within given limits of machine & tool constrains.

The adaptive controls are feed by signals of following two sensors,

a) Tool vibration sensor measuring vibrations of tool by accelerometer

mounted on the machine spindle housing.

b) Spindle torque sensor which measure strain gauges mounted on machine

spindle.

Important constraints for ACC system:

1. Max. & Min. spindle speed.

2. Max. allowed torque.


97

3. Max. & Min. allowed chip load.

4. Max. permitted feed rate.

5. Impact chip load.

6. Max. Allowed vibrations.

Advantages of ACM system

1. Increased production rate:

On line adjustments to allow for variations in work geometry, material & tool

wear provide the machine with the capacity to achieve highest metal removal rates

that are consistent with existing cutting conditions.

2. Increased tool life:

Because adjustments are made in the feed rate to prevent severe loading of

the tool, fewer cutters will be broken.

3. Greater part protection:

Instead of setting cutter force constraint limit on the basis of max. Allowable

cutter & spindle deflection, the force limit can be established on the basis of work

size tolerance.

4. Less operator invention:

Transfer of control over the process into the hands of management via the

part programs.

5. Easier part programming:

The selection of feed is left to the controller unit rather that to the part

programmer. The programmer can afford to, take less conservative approach. Less

time is needed to generate the program for the job & fewer layouts are required.


98

SPECIFICATION AND FEATURES OF CNC MACHINE

JYOTI CNC TURNING CENTER (DX-350)

Key Features

In today's competitive market, you need to produce world class products quickly, accurately and

with the minimum of non-productive time.

You can find a range of high technology CNC Lathes that deliver the fastest throughput you need

in DX series manufactured by JYOTI. These machines are a result of continuous developments

and innovations we have made in the field of machine tool ever since we started manufacturing

CNC Lathes, compiling and considering the customer feedbacks and incorporating our own

innovations.

Technical Specifications

Capacity

Swing Over Bed 700 mm

Maximum Turning Length 1500 mm

Std. Turning Dia 400 mm

Max.Turning Dia. 500 mm

Slides

X axis Travel 250 mm

Longitudinal (Z axis) Travel 1700 mm

Rapid Feed (X & Z axis) 24 M/min

Main Spindle

Spindle Motor Power 18.5 / 25.5 kW


99

(Continuous rating/30 min. rating)

Spindle Bore 80 mm

Spindle Nose A28

Max. Bar Capacity 65 mm

Speed Range 50-2500 rpm

Full Power Speed Range 500-2500 rpm

Turret

No. of Stations 8

Max. Boring Bar DIa 50 mm

Tool Size (Cross Sectional) 25 x 25 mm

Accuracy (asper VDI/DGQ 3441)

Positioning Uncertainty 0.010 mm.

Tail Stock

Quill Diameter 130 mm

Quill Stroke 150 mm

Thrust (adjustable) (max) 500 kgf

Other

Weight (Approx.) 10000 Kg

Dimension (Approx.) (LxWxH) 4615 x 2081 x 2060 mm

Standard Features

› AC Spindle Drive

› Monoblock Structure


100

› L. M. Guideways (Roller Type)

› 8 Station Bi-directional Turret

› Tailstock with hydraulic quill

Controller System

› SINUMERIK - 802D

Productivity Improvement Options

› Chip Conveyor

› Bar Feeder

› Bar Puller

› Tool Life Management

› Live Tool Turret

› 12 Station Bi-Directional Turret

› A211 Spindle Nose

› FANUC

› Live Center

› Slant rigid monoblock structure to absorb torsion and vibration enables hard part machining.


101

JYOTI CNC MACHINING CENTER (VMC1260):

Key Features

To match the demand of greater accuracy and total reliability at higher speeds JYOTI has

developed special performance series Vertical Machining Centers. These rigid machines are broad

based C type structure machines, with a moving table for easy access. The high dynamic structure

supports rapid axes take-offs 2 with an acceleration of 5m/s . Hi-tech features like linear scale

feedback and through coolant, high speed motorized spindle are incorporated in these machines as

available options.

Technical Specifications

Table

Table Size 1400 x 630 mm

T-slot-dimension 5 x 18 x 125 mm

Distance from Floor to Table 1075 mm

Max. load on table 1200 kgf

Capacity

X axis travel 1220 mm

Y axis travel 600 mm

Z axis travel 610 mm

Dist. from Spindle Face to table top 150-760 mm

Main Spindle

Spindle Speed 0 - 8000 rpm

10.5 kw / 13.5 kw (Con./30min.)


102

Spindle Power

Front Bearing Bore 70 mm

Spindle Nose BT-40

Accuracy (as per VDI/DGQ 3441)

Positioning Uncertainty 0.010 mm.

Feed

Rapid Traverse (X, Y & Z) 24 m/min

Cutting Feed 10 m/min

Automatic Tool Changer

Number of Tools 20

Tool Dia. Max. 80 mm

Tool Weight Max. 7 kg

Tool Length Max. 250 mm

Other Data

Weight (Approx.) 10,200 Kg

Dimension (Approx.) (LxWxH) 2830 x 3140 x 2990 mm

Standard Features

› CNC SIEMENS SINUMERIK 810D

› AC Spindle Drive

› AC SERVO Axis Drive

› L.M.Guide Ways

› Auto & Manual Coolant System

› Centralized & Programmable Lubrication


103

› Laser Calibrated axis for high precise positing accuracy and Repeatability

› Electricals with quality devices & panel with A.C.

› Work Light

Options

› Fully tooled up solutions to meet the customer needs & Tool life management

› Chip Conveyor

› APC

› 4 & 5 axis option

› High speed spindle upto 12000 rpm with chiller

› Flood Coolant System

› Collant through Spindle

› CNC System Fanuc 0iMC


104

AIM: MANUAL PART-PROGRAMMING FOR CNC TURNING CENTER AND

MACHINING CENTER.

FUNDAMENTALS OF CNC PROGRAMMING:

PROGRAM NAMES:

When creating a program, the program name can be freely selected if the following

conventions are used.

First two characters must be letters.

The remaining character may be letters, digits or underscore.

Do not use any separators (space) between two characters.

Maximum 16 or more characters are permitted depending upon the control unit.

PROGRAM STRUCTURE:

The NC program consists of a sequence of blocks. Each block constitutes a

machining step.

Statements in block are written in the form of words. The last block on the order of

execution of blocks contains a special word for the program end.

Program structure

Block Word Word Word ….. :Comment

Block N10 G00 X30 .......... 1st Block

Block N20 G01 Z58 .......... 2nd Block

Block N30 G91 .......... .......... 3rd Block

Block N40 M2 .......... :End of program

GANPAT UNIVERSITY




M. T .


ECH CAD- CAM



105

A word is a block element and mainly constitutes a control command. The word

consists of address character and numerical value consists of a sequence of digits.

Block Word Word Word

Address Value Address Value Address Value

Example of block G01 X -23.8 F400

Explanation Transverse using

linear interpolation

Travel or limit

position for the X

axis -23.8 mm

Feed : 400 mm/min

BLOCK STRUCTURE:

A block structure contains all data required to execute a step of machining. Block

generally consists of several words and we are always completed with the end-of-block

character “Lf”. This character is automatically generated when pressing the line space key or

the input key on writing.

The block may contain any or all the following:

Sequence or block number (N)

Preparatory functions (G)

These are the codes which prepare the machine to perform a particular

function like Positioning, contouring, thread cutting and canned cycling.

Dimensional information (X, Y, Z, etc)

Decimal point (.)

Feed rate (F)

The rate at which the cutter travels through the material is specified in

mm/min or mm/rev.

Spindle speed (S)

This may indicate either the spindle rpm or the constant cutting speed in

m/min

Tool number (T)


106

For machines having automatic tool changers or turrets, the T word calls a

particular toll that has to be used for cutting.

Tool offset function (D)

This word activates the cutter radius and length compensations.

Miscellaneous functions (M, H, etc)

End of block (EOB)

If a block contains several statements, the following order is recommended for them.

N… G… X… Z… F… S… T… D… M… H…

Block number should be selected in steps of 5 or 10 in ascending order.

BLOCK SKIP:

Block of a program, which are not to be executed with each program run, can be

marked by a slash ― / ‖ in front of the block number. If block skip is active during program

execution, all blocks marked with ― / ‖ are skipped. The program is continued with the next

block without marking.

PREPARATORY FUNCTIONS (G CODES):

G00 – Linear interpolation at rapid transverse

G01 – Linear interpolation at given feed rate

G02 – Circular interpolation in clockwise direction

G03 – Circular interpolation in counter clockwise direction

G25 – Lower spindle speed limiting or lower work area limiting

G26 – Upper spindle speed limiting or upper work area limiting

G33 – Thread cutting with constant lead

G40 – Tool radius compensation OFF

G41 – Tool radius compensation left to contour

G42 – Tool radius compensation right to contour

G54 – Select zero offset 1


107




G60 – Exact stop

G64 – Continuous path mode control mode

G70 – Input data system in inch

G71 – Input data system in metric

G700- Inch data input also for feed F

G710- Metric data input also for feed F

G74 – Reference point approach

G75 – Fixed point approach

G90 – Absolute dimension programming

G91 – Incremental dimension programming

G94 – Feed rate F in mm/min

G95 – Feed rate F in mm/spindle revolutions

G96 – Constant cutting speed ON

G97 – Constant cutting speed OFF

MISCELLANEOUS FUNCTION ( M-CODES ):

M00 – Unconditional program stop

M01 – Conditional program stop

M02 – End of program with return to program start

M03 – Spindle rotation, in clockwise direction

M04 – Spindle rotation, counter clockwise direction

M05 – Spindle stop

M06 – Tool change at reference point

M16 – Tool change at current location

M08 – Coolant ON

M09 – Coolant OFF

M30 – End of program


108

ABSOLUTE INCREMENTAL DATA INPUT WITH G90, G91, AC, IC

G90 – Absolute data input modal

G91 – Incremental data input modal

Z=AC(..) Absolute data input for certain axis(here Z-axis) non-modal

Z=IC(..) Incremental data input for certain axis(here Z-axis), non-modal

With absolute data input the dimensions are specified with reference to the zero

point of the currently active coordinate system. With program start, G90 is active for all axes

and remain active until it is canceled in a later block by G91.

With incremental data input, the numerical value of the positional information

corresponds to the distance to be traversed by the axis. The sign specifies the traversing

direction. G91 is active for all axes and remains active until it is canceled in a later block by

G90.

G90 – Absolute dimension G91 – Incremental dimension

PROGRAMMING EXAMPLE:

N10 X18 Z32 : By default absolute data input

N20 X60 Z=IC(38) : X dim. Still remain absolute, Z incremental dimension

N30 G91 X23 Z23 : Switch over to incremental data input for both X and Z

N40 X=AC(-44) Z12 : X dim. Absolute Z dim. Still remains incremental

N50 G90 : Switch over to absolute data input for all axis.


109

METRIC AND INCH DIMENSIONS: G71, G70, G710, G700

If the work piece dimensions are other than the basic system of the control system

(inch or mm). You can enter the dimension directly into the program. The required

conversion into the basic system is carried out by the control system.

Programming:-

G70 : inch dimensions

G71 : metric dimensions

G700 : inch dimensions, also for feed F

G710 : metric dimension, also for feed F

Programming example:-

N10 G70 X12 Z35 : inch dimension for both X and Z

N20 X44 Z55 : G70 still active

…..

N80 G71 X21 Z20.5 : metric dimension from here

Depending on the basic scaling setting, the control system interprets all geometrical

values as metric or inch dimensions. Tool offsets and settable zero offsets including the

corresponding displayed values are also to be understood as geometrical values; this also

applies to the feed F specified in mm/min.

G70 or G71 interprets all geometrical data specified directly with reference to the

work piece in inches of metrically, e..: X, Y, Z, G01, G02, G03, G33, CIP, CT

RADIUS DIAMETER PROGRAMMING: DIAMOF, DIAON

When parts are machines on turning machines, the positional data for the x axis are

usually programmed with diameter dimensions. If necessary it is possible to switch over to

radius programming DIAMOF and DIAMON will evaluate the specification for the X axis

as radius or diameter input.

Programming:-

DIAMON : Diameter input

DIAMOF : Radius input


110

Programming Example:-

N10 DIAMON X35 Z35 : For X axis – Diameter input

N20 X40 Z25 : DIAMON is still active

N30 DIAMOF : Switchover to radius input for X axis

N40 X20 Z35 : DIAMOF is still active

LINEAR INTERPOLATION AT RAPID TRAVERSE: G00

The Rapid traverse movement G00 is used for quick positioning of the tool, not for

direct work piece machining. All axes can be traversed at the same time, resulting in a straight

path.

The maximum speed (rapid traverse) for each axis is defined in machine data. If only

one axis traverse, it will traverse as its rapid traverse. If two axes simultaneously traverse, the

tool path federate (e.g. resulting speed at the tool tip) will be selected such that the maximum

possible tool path feedrate results, with consideration of all axes involved.

A programmed feed (F word) is not relevant for G00. G00 is effective until it is

canceled by another statement from this group (G01, G02, G03, …..).


N 10 G00 X110 Z60

LINEAR INTERPOLATION WITH FEED: G01

The tool moves from the starting point to be end of point along a straight path. For

the tool path federate, the programmed F word is decisive.

All axes can be traversed at the same time.

G01 is effective until it is cancelled by another statement from the G group (G00, G02, G03,

…..).


111


N10 G54 G00 G90 X45 Z190 S400 M3 : Tool traverse at rapid traverse spindle

speed-500 rpm, CW rotation

N20 G01 Z110 F0.2 : linear interpolation with feed 0.2

mm/rev

N30 X50 Z100

N40 Z85

N50 G00 X 110 : Clearance at rapid traverse

N60 M02 : end of program

CIRCULAR INTERPOLATION:

With G02 and G03 the tool moves from the starting point to the end point on

circular path. The direction is determined by the G function.

The description of the desired circle can be specified in different ways.

G02/G03 is active until it is canceled by another statement of this G group (G00, G01, …..).

For tool path velocity the programmed F word is decisive.

The different ways to define a circle are shown below.

Center and end point specification for circle:-


112


N10 G90 Z30 X40 : Start point of circle for block N20

N20 G02 Z50 X40 K10 : End point and centre point

End point and radius specification for circle:-


N10 G90 G01 Z30 X40 F1.4 : Start point of circle for block N20

N20 G02 Z50 X40 CR=12.207 : End point and circle radius

Negative sign for the value of CR will select a circle segment greater then a semi circle.

End point and aperture angle specification for circle:-


113



N20 G02 Z50 X40 AR=105 : End point and aperture angle

Centre point and aperture angle specification for circle:-



N20 G02 I-7 K10 AR=105 : Centre point and aperture angle

Circular interpolation via intermediate point:-


114

With CIP, the direction of the circle results from the position of the intermediate

point. CIP is effective until it is canceled by another statement from this group (G00, G01,

G02, …..).


N10 G90 G00 X40 Z30 : Starting point of circle for N20

N20 CIP X40 Z0 K1=40 II=45 : End and intermediate points

THE CUTTING WITH CONSTANT LEAD: G33

The function G33 can be used to machine threads with constant lead of the following type.

Thread on cylindrical bodies

Thread on taper bodies

External and internal threads

Single and multiple threads

This requires a spindle with position measuring system. G33 is effective until it is

canceled by another statement of this group (G00, G01, G02, …..).

RH or LH threads are defined with the direction of rotation of spindle

M03 – CW rotation M04 – CCW rotation

For thread length, the run-in and run-out travels should be taken into account.

For G33 threads, the velocity of the axis is decided by the set spindle speed and programmed

thread lead.


115

STOCK REMOVAL CYCLES:

Turning Stock Removal Cycle: CYCLE95

Name of Contour Subroutine

In-feed Depth with out sign

Finishing allowances along longitudinal axis

Finishing allowances along Facing axis

Finishing allowances Suitable for Contour

Feed Rate for Roughing

Feed Rate for Finishing

Operation

Dwell time to Chip brake during Roughing

Path for Roughing interrupted

Retract Path from contour, Incremental

Thread Cutting Stock Removal Cycle: CYCLE97

Thread Lead as a Value

Thread Lead as Thread size

Thread Starting Point along longitudinal Axis

Thread End Point along longitudinal Axis

Diameter as thread starting

Diameter at thread end point

Run In Path

Run Out Path

Thread Depth

Finishing Allowances

In-feed Angle


116

Number of roughing Cut

Number of finishing Cut

FIXED-POINT APPROACH: G75

G75 is used to approach a fixed point in the machine, e.g. tool change point. The

position is fixed in the machine data for all axes. No offset is effective. The velocity of each

axis is rapid traverse. In the block following G74 the previous G command of the

interpolation type group is active.

Programming Example:- N10 G75 X1=0 Z1=0

REFERENCE POINT APPROACH: G74

It is used for reference point approach in the NC program. Direction and speed are

stored in machine data. Both G74 and G75 requires separate block and are effective block by

block.

Programming Example:- N10 G74 X1=0 Z1=0

FEED F:

The feed F is the tool path feed rate and represents the amount of geometrical total

of the speed component of all axes involved.

The feed F is active for the interpolation types G1 G2 G3 CIP CT and remains

stored until a new F word is programmed.

The unit of F is determined by G functions.

G94 : F as feed in mm/min G95 : F as feed in mm/rev of the spindle

It is only active if spindle is rotating


N10 G94 F25 : Feed in mm/min


117

N20 S200 M03 : Spindle Rotation

N30 G95 F10.5 : Fees in mm/rev

SPINDLE SPEED S:

The speed of the spindle is programmed in revolutions per minute under the address

S provided the machine has a controlled spindle.

` The direction of rotation and the beginning or the end of the movement are defined

using M commands.

M03 : CW rotation of the spindle

M04 : CCW rotation of the spindle

M05 : Spindle Stop

The axis movements start only if the controlled spindle has accelerated with M03 or M04.

N10 G01 X70 Z20 F1.8 M03 S300 : First the spindle accelerates in CW direction

to 300rpm and then axes X and Z traverse.

N20 S500 : Spindle speed change

N30 X100 M05 : X movement and spindle stop

CONSTANT CUTTING SPEED: G96, G97

Prerequisite:

This function requires a controlled spindle.

With the function G96 enabled, the spindle aped will be adapted to the diameter of

the work-piece currently machined (face axis) such the a programmed cutting speed S at he

tool edge remain constant (spindle speed by diameter = constant).


118

From the block containing G96, the S word will be interpreted as the cutting speed.

G96 is modally active until it is disabled by another G function of the group (G94, G95 and

G97).

G96 S….. LIMS=….. F….. : Constant speed ON

G97 : Constant cutting speed OFF

Where,

S = Cutting speed, unit m/min

LIMS = upper speed limit of spindle

F = Feed in mm/rev. as with G95

When traversing with G00 (Rapid traverse), the spindle speed is not changed.

When machining from larger diameter towards smaller diameter, the spindle speed

may rapidly increase. So it is recommended to specify the upper spindle speed limiting using

LIMS.

The function constant cutting speed-G96 is disabled by G97. With G97 the S word is

treated as spindle speed.


N10 M03

N20 G96 S100 LIMS=2000 : Constant cutting speed ON

100 m/min, Spindle speed limit = 2000

N30 G00 X100 : No speed change because of G00

N40 X60 : Contour approach. New speed automatically be

set such, as required for the start of block N50

N50 G01 X30 F0.5 : Feed 0.5 mm/rev

N60 G97 X100 : Disable constant cutting speed

N70 S1000 : New spindle speed, rpm

Round and Chamfer:-

For chamfer or rounding the corresponding word CHF=….. or RND=….. is

programmed in the block containing axis movements leading to the corner.


119

CHF=….. : Insert chamfer with length of chamfer

RND=….. : Insert rounding with radius of rounding

Programming Example for Chamfer:-

N10 G01 Z10 CHF=5 : Insert chamfer of 5 mm

N20 X20 Z40

Programming Example for Rounding:-

N10 G01 Z10 RND=8 : Insert radius with 8 mm radius

N20 X20 Z40


120

EXAMPLE OF CNC TURNING CENTER PART PROGRAMMING:

20/1

2/20

11


121

20/1

2/20

11


122

AIM: STUDY OF CAD CAM INTEGRATION.

INTRODUCTION TO CAD/CAM INTEGRATION:

Automation of computer -aided design and computer aided manufacturing as

separate entities do not lead to optimum solutions of manufacturing attributes. The

engineering design function has to be integrated with manufacturing operation to ensure

design engineer has knowledge of capabilities of manufacturing to implement specific

designs into finished products. Similarly, the manufacturing engineer needs to know the

requirements of the design in a clear and legible manner.

The biggest change in recent times for the CAD/CAM industry lies with the term

"integration." The CAD model data generated during the design process can be utilized

further by the Computer Aided Manufacturing process. A good CAD/CAM system

eliminates the need to manually calculate tangencies or to do the trigonometry required to

calculate tool paths, saving valuable programming time. It also provides a consistent finish

and predictable results.

Integration plays a very important role in the future of CAD/CAM products. There

have been big workstation-based integrated CAD/CAM systems around for many years.

They provide CAD and CAM integration by providing all pieces from the same company.

But now there is a new group of products touting integration as a key issue. They pursue

integration through other means than single brand products.

What is CAD/CAM integration? Is it good? Do you need it? It all depends on the

type of integration you're thinking about and what your needs are. To understand

CAD/CAM integration today, it makes sense to start with the functions that need to be

integrated.

GANPAT UNIVERSITY




M. T .


ECH CAD- CAM



123

The term CAD (computer-aided design) is widely used to describe any software

capable of defining a mechanical component with geometry, surfaces or solid models. CAM

(computer-aided manufacturing) is software used to develop NC programs. There are other

types of CAD and CAM, but for our purposes here, only mechanical CAD and CAM will be

discussed.

PURPOSES FOR USING CAD/CAM:

Design Modeling:-

A mechanical design engineer uses CAD software to create a part. This definition of

the part can be called its model. This model can be represented as a drawing or a

CAD data file. (See Figure 1.)

Manufacturing Modeling:-

A manufacturing engineer or NC programmer uses CAD software for a

number of important tasks. Perhaps most common is to develop a computer model

of a part that was previously defined only by a drawing. Another common task is to

evaluate and repair existing CAD data so that it is usable for manufacturing functions.

Manufacturing engineers also sometimes create new part models from the original

design to allow for manufacturability. This includes adding draft angles or developing

Fig. 1--This solid model

of a plastic remote

control housing is a

good example of what

design engineers create.


124

models of the part for different steps in multi-process manufacturing. And, of course,

someone on the manufacturing side must design models of fixtures, mold cores and

cavities, mold bases and other tooling. (See Figure 2.)

NC Programming:-

A manufacturing engineer or NC programmer uses CAM software to select

tools, methods and procedures to machine the models defined in the manufacturing

modeling section described above. Note that whoever performs manufacturing

modeling is usually the same person that performs NC programming. (See Figure 3.)

In a perfect world you would select up to three different software products,

each ideally suited to one of these functions, and they would all interact perfectly.

Unfortunately, this is not a perfect world. For these different products to work well

Fig. 2--The core (left) and cavity for the remote

control show what manufacturing modeling needs

to be done before a part can be machined.

Fig. 3--These machining routines for the core

(left) and cavity are examples of what the NC

programmer creates.


125

together, they need to possess a high level of integration. There are three different

types of integration to consider:

DIFFERENT TYPES OF INTEGRATION:

Data integration:-

Data integration is the ability to share part models (common data files or a common

database). This is the most important type of integration for CAD/CAM. A standards-based

surface file such as IGES is a relatively poor means to data integration due to the amount of

manual repair work frequently required when a file is passed from one system to another.

(See Figure 4.) A better means to data integration right now is a proprietary, but widely

available file format, such as a Parasolid file. Because such formats are tightly defined, data

transferred from one Parasolid-based software program to another comes through flawlessly.

(See Figure 5.) Two Parasolid-based software programs sharing one Parasolid data file is

even better, as both model‘s history and associability can be maintained.

Fig. 4--IGES files often come in with many problems that

need to be repaired before the part can be machined.

These pictures show an IGES file for a part with gaps

between the surfaces.


126

Interface integration:-

Interface integration is a common look and feel for different software modules. This

reduces the learning curve for a common user of the different modules.

Application integration:-

Application interface is the way in which different software modules work together for

a single user. This can be achieved by having the different functions physically in the

same computer program ("same" application or "inside" application integration). It can

also be achieved with technology like OLE (object linking and embedding), which

allows two different computer programs to work closely together, appearing seamless

to the user (CAM "beside" CAD).

HOW INTEGRATION STARTED:

In the beginning, there were only CAD systems, and engineers used them to draw

pictures of parts. The first CAM systems helped an NC programmer, machinist or

manufacturing engineer program from these drawings. This making of drawings, and

programming parts from drawings, was (and still is) time consuming and subject to a lot

of human error. Then someone got the bright idea to eliminate this to-and-from drawing

step, and the integrated CAD/CAM system was born.

Until recently, integrated CAD/CAM meant buying the same brand of CAD and CAM

products. A number of software vendors provide such products today, many of which

offer high power and sophistication, but also come at a rather high price and require a

workstation computer to run effectively. These products typically provide data, interface

and application integration. Because of their cost and complexity, however, these

Fig. 5--Solid modeling

is a superior method of

data exchange because,

by definition, parts are

not allowed to contain

problems like gaps,

cracks and overlaps.


127

products do not provide ideal solutions for everyone. In addition, once the customer

picks the CAD product he likes best, he's kind of stuck with whatever CAM product they

have. No mixing and matching of products is allowed if the user wants to retain the

advantages of full integration.

The disadvantages of the traditional integrated workstation-based CAD/CAM system

have contributed to the growth of the stand-alone CAM market as we know it today.

These CAM products focus on NC programming, or both manufacturing modeling and

NC programming. In general they are easier to use and less expensive than their

workstation-based brethren. This class of product has grown in sophistication to rival the

capabilities of the traditional integrated CAD/CAM system, while still maintaining the

advantages of simplicity, efficiency and cost. The only problem stand-alone CAM

systems have suffered from is a lack of integration with the original design modeling

CAD system, and a lack of ability to access the CAD market. Now that is changing.

THE NEW CAD MARKET:

The PC has been home to CAD software for decades. This CAD software has been

primarily 2D drafting and 3D wireframe CAD, with a few surface modeling products

as well. While PC-based CAD has been a success story in its own right, it has never

made the step up to providing significant competition to the workstation-based CAD

market. But things have changed in recent times.

It all started with Windows NT and fast PCs like the Pentium Pro, helped along by

low-priced RAM (random access memory). Then users of workstation-based CAD

began to see the benefits of the PC's low purchase cost, low maintenance cost, ease

of use, ease of networking and performance. While the PC was not faster then a

workstation yet, it did offer an excellent combination of price and performance. And

so it didn't take long before someone realized these PCs were now capable of

running the same solid modeling technology used in the major workstation-based

CAD products.

UNIX-based products held 62 percent of the CAD/CAM market in 1997, down

from 67 percent in 1996. Windows NT was estimated to have 23 percent of the

CAD/CAM market in 1997, up from 17 percent in 1996. The total number of UNIX

seats grew 9 percent in 1997. The total number of Windows seats grew 59 percent in

1997. With such a massive difference in growth rates, it is clear that UNIX is rapidly


128

being overtaken by Windows NT as the dominant CAD/CAM platform.

Another key change in the CAD/CAM market is the advent of the third-party solid

modeler. Solid modeler kernel companies like Spatial Technologies (ACIS),

Unigraphics (Para solid) and Ricoh (Design base) began selling to solution providers

who started focusing on the mid-range CAD market. In 1995, Solid Works and

Intergraph Solid Edge were introduced and a new era of solid modeling CAD began.

They weren't alone for long. New product announcements have become common,

with all major CAD companies jumping into this new market. Bentley introduced

MicroStation Modeler. Parametric Technology renamed their Pro/E Jr. as PT

Modeler to better be perceived as a mid-range CAD player. Computervision

introduced DesignWave, and was purchased by Parametric Technology. SDRC

introduced their Artisan series and purchased Camax to provide more CAM

technology. Dassault (Catia) has announced their intent to field a Windows NT

product and recently purchased SolidWorks.

Not only does solid modeling technology fuel the rapid growth of all of these new

products, it also provides a backbone for seamless data transport between compatible

products.

CAM IN THE NEW CAD MARKET:

CAM products are also moving into this solid modeling CAD world. Some CAM products

have plotted the shortest possible path to a marketing claim of "solids-based solution." In

several cases, this path has lead to an "inside" CAD application version of a product, where

most of the CAM capabilities are actually placed within the CAD software.

There is another alternative. Any CAD or CAM product based on the same modeler (solid

modeling kernel) can exchange data as well as the big workstation systems do, providing a

high level of data integration between different brands of products for the first time. (See

Figures 6, 7 and 8.) Solid model standards include Spatial Technologies' ACIS (.sat file s) and

Parasolid (.x_t and .xmt files) and Ricoh's Designbase. These standards are becoming widely

supported.

http://www.mmsonline.com/dp/showroom/index.cfm?code=SDRC&lcode=ML


129

OLE and OLE for D & M (for design and manufacturing) is another Windows technology

becoming popular. This capability allows a CAM product to directly "ask" a CAD system for

model data without the hassles of saving and opening files, or the technical problems of file

translations. It is another powerful tool for providing data and a level of application

integration.

Fig. 6--A part created in

SolidWorks (a

Parasolid-based CAD

system) is directly read

by Virtual Gibbs (a

Parasolid-based CAM

system). The part file is

courtesy of SolidWorks.

Fig. 8--Here the core is

being machined by

Virtual Gibbs.

Fig. 7--This core was

created from the

SolidWorks part shown

in Figure 6. The data

integration between the

products provides a

high level of

integration.


130

Historically, CAD/CAM solutions have achieved high levels of integration by putting all

functions in the same computer program. This is one reason why some people think that

there are big advantages with same-application integration for CAD/CAM. However, today's

technology provides flexible alternatives to the old same-application approach. Solid models

and OLE provide excellent integration between different applications. Windows NT/95

offers excellent interface integration.

WHO NEEDS AUTOMATION?

A job shop machines other people's designs, created on other people's CAD systems. A job

shop does not have a primary design modeling CAD need and therefore derives little value

from interface or application integration with other people's CAD systems. Data integration

with other people's CAD systems is very valuable, however, and a prime concern. Job shops

have to deal with a wide variety of data types from a variety of sources. The ability to import

and repair data from many sources is vital. A job shop needs manufacturing modeling and

CAM capabilities.

For a small integrated manufacturer—that is, a company where one person is doing the primary

product design modeling, the manufacturing modeling and the NC programming on a single

computer—data integration between CAD and CAM is also the most important issue. In

addition, the user gets advantages from application and interface integration with his CAD

product.

A general manufacturer has separate individuals performing design modeling, manufacturing

modeling and CAM, and in many cases these functions are performed in entirely different

departments. These companies range from job-shop-like departments supporting a wide

range of internal CAD formats to departments that utilize the same CAD as the design

department for maximum integration. Data integration is the common issue.

INTEGRATION BY PROCESS PLANNING:

Process planning is the interface between design and manufacturing process. Process

planning lists a sequence of manufacturing and assembly processes that will be used to

produce a part or assembly. For each operation it describes details such as which material will

be used, which machine will be used, which setting, etc.


131

STEPS:

1. Select raw materials.

2. Identify volumes of material to be removed.

3. Identify the set of machining processes from the available standard machining

processes that can remove the required volumes.

4. Generate the most effective/efficient sequence of machining operations.

EXAMPLE OF PROCESS PLANNING:


132

THREE APPROACHES FOR CAPP:

There are three approaches for computer aided process planning.

1. Manual approach

2. Variant approach

3. Generative approach

MANUAL APPROACH:

Process plan is developed by skilled operator who is familiar with company‘s

manufacturing capabilities. The steps involved are:

1. Study the overall shape of part.

2. Determine what stock material is used.

3. Identify the datum surfaces for setups.

4. Identify part features.

5. Group features into setups.

6. Sequence the operations in setups.


133

7. Select tool for each operations.

8. Determine fixtures for each setup.

9. Final check.

VARIANT APPROACH:

In variant approach computer sore match the existing process plans. In the variant

approach, parts that have similar features are grouped into families. There is a standard

plan for each family. A process plan is found by:

1. Identify the important features of the part.

2. Identify which family the parts belong to.

3. Retrieve the standard plan.

4. Edit the standard plan if required.

Variant approach is advanced manual approach to process planning. Planner‘s workbook

is stored in computer file. Variant approach requires standard database of process

planning for each family of part.

Group Technology simplifies the problem of finding out which family part belongs to. In

GT a code is assigned to part based on features it contains.

GENERATIVE APPROACH:

Generative approach requires the computer to perform the following steps.

Enter the design specifications.

-input/recognize the stock material.

-recognize the machining features.

Generate the process plan.

-determine the optimal setups.

-determine the optimal sequence of operations

-determine the optimal fixtures type and setups.

Generative approach is not widely used because

-requires information (such as tolerances) which are not available in CAD model.


134

-a lot of knowledge must be added to the system to make it capable to handle

different types of parts.

-evaluating all the combination of the possibilities is computationally intense.

HOW TO DECIDE WHAT IS RIGHT FOR YOU ?

The first step in deciding what is right for your shop is to understand that you now have

options. You are no longer trapped into buying a large, expensive, workstation-based

CAD/CAM system if it is not right for your needs. Nor do you have to settle for less than

adequate data translations from stand-alone products. Examine your needs. Do you get most

of your CAD files from a variety of sources? Or do you receive CAD files primarily from a

single source? Then look around for the CAD and CAM products that fit the needs of your

shop best—focusing on ease of use and suitability to the type of work that you do. Armed

with the facts and the new capabilities available to you, you are ready to make an informed

choice.


135

AIM: TO STUDY INTRODUCTION OF NETWORKING AND

COMMUNICATIONS.

INTRODUCTION

Communication is the desire of man. When human voice became inadequate, ancient

civilizations devised drum codes and smoke signals to send information to far off distances.

These primitive methods have given way to sending messages through electronic pulses. A

stand-alone computer communicates very efficiently by connecting it with other computers.

Data in a computer is transmitted to another computer located across continents almost

instantaneously using telephone, microwaves or radio links. The long distance

communication link between a computer and a remote terminal was set up around 1965.

Now networking has become a very important part of computing activity.

NETWORK

A large number of computers are interconnected by copper wire, fiber optic cable,

microwave and infrared or through satellite. A system consisting of connected nodes made

to share data, hardware and software is called a Computer Network.

SOME IMPORTANT REASONS FOR NETWORKING

Sharing of resources: Primary goal of a computer network is to share resources. For

example several PCs can be connected to a single expensive line printer.

Sharing information: Information on a single computer can be accessed by other

computers in the network. Duplication of data file on separate PCs can be avoided.

Communication: When several PCs are connected to each other, messages can be sent and

received. From a remote location, a mobile salesman can relay important messages to the

GANPAT UNIVERSITY




M. T .

EXPERIMENT NO: 9

DATE: ..../..../........

ECH CAD- CAM



136

central office regarding orders. Relevant databases are updated and the business

commitments are fulfilled.

APPLICATIONS OF NETWORK

The following are the areas where computer networks are employed.

Electronic data interchange

Tele-conferencing

Cellular telephone

Cable Television

Financial services, marketing and sales

Reservation of Airlines, trains, Theatres and buses

Telemedicine

ATM

Internet banking

Several educational institutions, businesses and other organizations have discovered

the benefits of computer networks. Users can share data and programmes. They can co-

operate on projects to maximize the usage of available expertise and talent.

BENEFITS OF NETWORK

Effective handling of personal communications

Allowing several users to access simultaneously important programs and data:

Making it easy for the users to keep all critical data on shared storage device and

safeguard the data.

Allowing people to share costly equipment.

The computer communication should ensure safe, secure and reliable data transfer.

Safe: The data received is the same as the data sent Secure : The data being transferred

cannot be damaged either will fully or accidentally.

Reliable: Both the sender and the receiver knows the status of the data sent. Thus the

sender knows whether the receiver got the correct data or not.


137

TYPES OF NETWORK

The following are the general types of networks used today.

Local Area Network (LAN)

Metropolitan Area Network (MAN)

Wide Area Network (WAN)

A network connecting systems and devices inside a single building or buildings close to

each other is called Local Area Network (LAN). Generally LANs do not use the telephone

network. They are connected either by wire or wireless. Wired connection may be using

twisted pairs, coaxial cables or Fiber Optic cables. In a wireless LAN, connections may be

using infrared or radio waves. Wireless networks are useful when computers are portable.

However, wireless network communicates slowly than a wired network.

The number of Computers in the network is between two to several hundreds. LAN

is generally used to share hardware, software and data. A computer sharing software package

and hard disk is called a file server or network server. A Network that spans a geographical

area covering a Metropolitan city is called Metropolitan Area Network (MAN) A WAN is

typically two or more LANs connected together across a wide geographical area. The

individual LANs separated by large distances may be connected by dedicated links, fiberoptic

cables or satellite links.


138

NETWORK TOPOLOGY

The network topology is the structure or layout of the communication channels that

connects the various computers on the network. Each computer in the network is called a

node. There are a number of factors that determine the topology suitable for a given

situation. Some of the important consideration is the type of nodes, the expected

performance, type of wiring (physical link) used and the cost. Network can be laid out in

different ways. The five common topologies are star, ring, bus, hybrid and FDDI.

Star Network : In a star network all computers and other communication devices are

connected to a central hub. Such as a file server or host computer usually by a Unshielded

Twisted Pair (UTP) cables.

Ring Network: In a ring network computers and other communication devices are

connected in a continuous loop Electronic data are passed around the ring in one direction,

with each node serving as a repeater until it reaches the right destination. There is no central

Host computer or server.


139

Bus Network: In a bus network all communication devices are connected to a common

cable called bus There is no central computer or server. The data transmission is

bidirectional.

Hybrid Network: A hybrid network is a combination of the above three networks suited to

the need.

FDDI Network: A FDDI network (pronounced as fiddly short for Fiber Distributed Data

Interface) is a high-speed network using fiber optic cable. It is used for high tech purposes

such as electronic images, high-resolution graphics and digital video. The main disadvantage

is its high cost.

BASIC ELEMENTS IN NETWORKING

All networks require the following three elements

1. Network services

Network services are provided by numerous combinations of computer hardware and

software. Depending upon the task, network services require data, input/output resources

and processing power to accomplish their goal.

2. Transmission media

Transmission media is the pathway for contacting each computer with other. Transmission

media include cables and wireless Technologies that allows networked devices to contact

each other. This provides a message delivery path.

3. Protocols

A protocol can be one rule or a set of rules and standards that allow different devices to hold

conversations.


140

COMMON NETWORK SERVICES

The following common network services are available.

File Services

Those are the primary services offered by the computer networks. This improves the

efficient storage and retrieval of computer data. The service function includes. · File transfer

Rapidly move files from place to place regardless of file size, distance and Local operating

system.

File storage and data migration – Increasing amount of Computer data has caused

the development of several storage devices. Network applications are well suited to control

data storage activity on different storage systems. Some data becomes less used after certain

time. For example higher secondary examination result posted on the web becomes less used

after a week. Such data can be moved from one storage media (say hard disc of the

computer) to another, less expensive media (say an optical disk) is called data migration.

File update synchronization – Network service keeps track of date and time of

intermediate changes of a specific file. Using this information, it automatically updates all file

locations with

the latest version.

File archiving – All organizations create duplicate copies of critical data and files in

the storage device. This practice is called file archiving or file backup. In case of original file

getting damaged, Computer Operator uses the Network to retrieve the duplicate file. File

archiving becomes easier and safe when storage devices are connected in the Network.

Print services

Network application that control manage access to printers and fax equipments. The

print service function includes · Provide multiple access (more than one user, use the

network) – reduce the number of printers required for the organization.

Eliminates distance constraints – take a printout at a different location.

Handle simultaneous requests – queue print jobs reducing the computer time.

Share specialized equipments-Some printers are designed for specific use such as

high-speed output, large size formals or colour prints. Specialised equipments may be costlier

or may not be frequently used by the user, when numerous clients are using the network,

printer use is optimized.


141

Network fax service – Fax service is integrated in the network. The computer in the

network sends the digital document image to any location. This reduces the time and paper

handling.

Message services

Message services include storing, accessing and delivering text, binary, graphic

digitized video and audio data. Unlike file services, message services deal actively with

communication interactions between computer users applications, network applications or

documents.

Application Services

Application services are the network services that run software for network clients.

They are different from file services because they allow computers to share processing power,

not just share data. Data communication is the process of sending data electronically from

one location to another. Linking one computer to another permits the power and resources

of that computer to be apped. It also makes possible the updating and sharing of data at

different locations.

COORDINATING DATA COMMUNICATION

The device that coordinates the data transfer is called Network interface card (NIC).

NIC is fixed in the computer and communication channel is connected to it. Ethernet,

Arcnet and token ring are the examples for the NIC. Protocol specifies the procedures for

establishing maintaining and terminating data transfer. In 1978, the International Standards

organization proposed protocol known as open system interconnection (OSI) . The OSI

provided network architecture with seven layers. The seven layers and the respective

functions. This architecture helps to communicate between Network of dissimilar nodes and

channels.


142

FORMS OF DATA TRANSMISSION

Data is transmitted in two forms

1. Analog data transmission

2. Digital data transmission

Analog data transmission is the transmission of data in a continuous waveform. The

telephone system, for instance, is designed for analog data transmission. Analog signal s are

sometimes modulated or encoded to represent binary data. Digital data transmission is the

widely used communication system in the world. The distinct electrical state of ‗on‘ and ‗off‘

is represented by 1 and 0 respectively. Digital data transmission as shown in Fig.6.6 is faster

and more efficient than analog. All computers understand and work only in digital forms 2

Data link Transmits data to Different networks 7 Application Purpose for communication


143

client/server 5 Session Starts, stops and governs Transmission order. 4 Transport Ensures

delivery of Complete message 6 Presentation Rules for data conversion 3 Network Routes

data to different networks 1 Physical

Passes bits on to Connecting median

MODEM

Computers at different parts of the world are connected by telephone lines. The

telephone converts the voice at one end into an electric signal that can flow through a

telephone cable. The telephone at the receiving end converts this electric signal into voice.

Hence the receiver could hear the voice. The process of converting sound or data into a

signal that can flow through the telephone wire is called modulation. The reverse process is

called demodulation. The telephone instrument contains the necessary circuit to perform

these activities. The device that accomplishes modulation – demodulation process is called a

modem. It is known that the electrical and sound signals are analog - which continuously

vary with time.

Equipments (DTE) are connected through modem and Telephone line. The modems

are the Data Circuit Terminating Equipments (DCE). DTE creates a digital signal and

modulates using the modem. Then the signals relayed through an interface. The second

modem at the receiving end demodulates into a form that the computer can accept. A

modem that has extra functions such as automatic answering and dialing is called intelligent

Modems.


144

Data Transmission Rate

The speed at which data travel over a communication channel is called the

communication rate. The rate at which the data are transferred is expressed in terms of bits

per second (bps)

Transmission Mode

When two computers are in communication, data transmission ay occur in one of the

three modes

Simplex mode

In simplex mode, data can be transmitted in one direction as shown in the figure.

The device using the simplex mode of transmission can either send or receive data, but it

cannot do both. n example is the traditional television broadcast, in which the signal is sent

from the transmitter to the TV. There is no return signal. In other words a TV cannot send a

signal to the transmitter.

Half duplex mode

In Half duplex mode data can be transmitted back and forth between two stations.

But at any point of time data can go in any one direction only. This arrangement resembles

traffic on a onelane bridge. When traffic moves in one direction, traffic on the opposite

direction is to wait and take their turn. The common example is the walky-talky, wherein one

waits for his turn while the other talks .


145

Full duplex mode

In full duplex mode a device can simultaneously send or receive data. This

arrangement resembles traffic on a two-way bridge, traffic moving on both directions

simultaneously. An example is two people on the telephone talking and listening

simultaneously. Communication in full duplex mode is faster. Full duplex transmission is

used in large computer systems. Products like ―Microsoft Net Meeting‘ supports such two

way interaction

INTERNET

Several networks, small and big all over the world, are connected together to form a

Global network called the Internet. Today‘s Internet is a network of about 50 million or

more computers spread across 200 countries. Anyone connected to the Internet can reach,

communicate and access information from any other computer connected to it.

Some of the Internet users are

Students

Faculty members

Scientists

Executives and Corporate members

Government employees.

The Internet protocol (IP) addressing system is used to keep track of the million of

users. Each computer on net is called a host. The IP addressing system uses the letter

addressing system and number addressing systems.

COMMUNICATION PROTOCOL

Internet is a packet-switching network. Here is how packetswitching works: A

sending computer breaks an electronic message into packets. The various packets are sent

through a communication network-often by different routes, at different speeds and

sandwiched in between packets from other messages. Once the packets arrive at the

destination, the receiving computer reassembles the packets in proper sequence. The packet

switching is suitable for data transmission. The software that is responsible for making the


146

Internet function efficiently is TCP/IP. TCP/IP is made up of two components. TCP stands

for transmission control protocol and IP stands for Internet Protocol.

TCP breaks up the data to be sent into little packets. It guarantees that any data sent to the

destination computer reaches intact. It makes the process appear as if one computer is

directly connected to the other providing what appears to be a dedicated connection. IP is a

set of conventions used to pass packets from one host to another. It is responsible for

routing the packets to a desired destination IP address.

COMMUNICATION

Today computer is available in many offices and homes and therefore there is a need

to share data and programs among various computers with the advancement of data

communication facilities. The communication between computers has increased and it thus it

has extended the power of computer beyond the computer room. Now a user sitting at one

place can communicate computers of any remote sites through communication channel. The

aim of this chapter is to introduce you the various aspects of computer network.

OBJECTIVES OF COMMUNICATION

After going through this lesson you will be in a position to:

explain the concept of data communication

understand the use of computer network

identify different components of computer network

identify different types of network

explain communication protocols

understand what is internet and email and its uses in modern communication

appreciate the use of satellite communication.

DATA COMMUNICATION

We all are acquainted with some sorts of communication in our day to day life. For

communication of information and messages we use telephone and postal communication

systems. Similarly data and information from one computer system can be transmitted to


147

other systems across geographical areas. Thus data transmission is the movement of

information using some standard methods. These methods include electrical signals carried

along a conductor, optical signals along an optical fibers and electromagnetic areas.

Suppose a manager has to write several letters to various clients. First he has to use

his PC and Word Processing package to prepare his letter. If the PC is connected to all the

client's PCs through networking, he can send the letters to all the clients within minutes.

Thus irrespective of geographical areas, if PCs are connected through communication

channel, the data and information, computer files and any other program can be transmitted

to other computer systems within seconds. The modern form of communication like e-mail

and Internet is possible only because of computer networking.

BASIC ELEMENTS OF A COMMUNICATION SYSTEM

The following are the basic requirements for working of a communication system.

1. A sender (source) which creates the message to be transmitted.

2. A medium that carries the message.

3. A receiver (sink) which receives the message.

In data communication four basic terms are frequently used. They are

Data: A collection of facts in raw forms that become information after processing.

Signals: Electric or electromagnetic encoding of data.

Signaling: Propagation of signals across a communication medium.

Transmission: Communication of data achieved by the processing of signals.

COMMUNICATION PROTOCOLS

You may be wondering how do the computers send and receive data across

communication links. The answer is data communication software. It is this software that enables

us to communicate with other systems. The data communication software instructs

computer systems and devices as to how exactly data is to be transferred from one place to

another. The procedure of data transformation in the form of software is commonly called

protocol.

The data transmission software or protocols perform the following functions for the efficient

and error free transmission of data.

1. Data sequencing: A long message to be transmitted is broken into smaller packets

of fixed size for error free data transmission.


148

2. Data Routing: It is the process of finding the most efficient route between source

and destination before sending the data.

3. Flow control: All machines are not equally efficient in terms of speed. Hence the

flow control regulates the process of sending data between fast sender and slow

receiver.

4. Error Control: Error detecting and recovering is the one of the main function of

communication software. It ensures that data are transmitted without any error.

DATA TRANSMISSION MODES

There are three ways for transmitting data from one point to another

1. Simplex: In simplex mode the communication can take place in one direction. The

receiver receives the signal from the transmitting device. In this mode the flow of

information is Uni.-directional. Hence it is rarely used for data communication.

2. Half-duplex: In half-duplex mode the communication channel is used in both

directions, but only in one direction at a time. Thus a half-duplex line can alternately

send and receive data.

3. Full-duplex: In full duplex the communication channel is used in both directions at

the same time. Use of full-duplex line improves the efficiency as the line turn-around

time required in half-duplex arrangement is eliminated. Example of this mode of

transmission is the telephone line.

DIGITAL AND ANALOG TRANSMISSION

Data is transmitted from one point to another point by means of electrical signals

that may be in digital and analog form. So one should know the fundamental difference

between analog and digital signals. In analog signal the transmission power varies over a


149

continuous range with respect to sound, light and radio waves. On the other hand a digital

signal may assume only discrete set of values within a given range. Examples are computer

and computer related equipment. Analog signal is measured in Volts and its frequency in

Hertz (Hz). A digital signal is a sequence of voltage represented in binary form. When digital

data are to be sent over an analog form the digital signal must be converted to analog form.

So the technique by which a digital signal is converted to analog form is known as modulation.

And the reverse process, that is the conversion of analog signal to its digital form, is known

as demodulation. The device, which converts digital signal into analog, and the reverse, is

known as modem.

Analog Signal

Digital Signal

ASYNCHRONOUS AND SYNCHRONOUS TRANSMISSION

Data transmission through a medium can be either asynchronous or synchronous. In

asynchronous transmission data is transmitted character by character as you go on typing on

a keyboard. Hence there is irregular gaps between characters. However, it is cheaper to

implement, as you do not have to save the data before sending. On the other hand, in the

synchronous mode, the saved data is transmitted block by block. Each block can contain


150

many characters. Synchronous transmission is well suited for remote communication

between a computer and related devices like card reader and printers.

MICROWAVE: Microwave system uses very high frequency radio signals to transmit data

through space. The transmitter and receiver of a microwave system should be in line-of-sight

because the radio signal cannot bend. With microwave very long distance transmission is not

possible. In order to overcome the problem of line of sight and power amplification of weak

signal, repeaters are used at intervals of 25 to 30 kilometers between the transmitting and

receiving end.

COMMUNICATION SATELLITE: The problem of line-sight and repeaters are overcome

by using satellites which are the most widely used data transmission media in modern days. A

communication satellite is a microwave relay station placed in outer space. INSAT-1B is such

a satellite that can be accessible from anywhere in India. In satellite communication,

microwave signal is transmitted from a transmitter on earth to the satellite at space. The

satellite amplifies the weak signal and transmits it back to the receiver. The main advantage

of satellite communication is that it is a single microwave relay station visible from any point

of a very large area. In microwave the data transmission rate is 16 giga bits per second. They

are mostly used to link big metropolitan cities.

TYPES OF CABLES:

TWISTED PAIR WIRE

The oldest, simplest, and most common type of conducted media is twisted pair

wires. Twisted pair is almost a misnomer, as one rarely encounters a single pair of wires. To

help simplify the numerous varieties, twisted pair can be specified as Category 1 -5 and is

abbreviated as CAT 1-5. While still a little away from being a published specification,

Category 6 twisted pair should support data transmission as high as 200 Mbps for 100

meters while Category 7 twisted pair will support even higher data rates. If you determine

that the twisted pair wire needs to go through walls, rooms, or buildings where there is

sufficient electromagnetic interference to cause substantial noise problems, shielded twisted

pair can provide a higher level of isolation from that interference than unshielded twisted

pair wire, and thus a lower level of errors.


151

COAXIAL CABLE

Coaxial cable, in its simplest form, is a single wire wrapped in a foam insulation,

surrounded by a braided metal shield, then covered in a plastic jacket. The braided metal

shield is very good at blocking electromagnetic signals from entering the cable and

producing noise. Because of its good shielding properties, coaxial cable is very good at

carrying analog signals with a wide range of frequencies. There are two major coaxial cable

technologies, depending on the type of signal each carries: baseband or broadband. Coaxial

cable also comes in two primary physical types: thin coaxial cable and thick coaxial cable.

FIBER OPTIC CABLE

Fiber optic cable (or optical fiber) is a thin glass cable approximately a little thicker

than a human hair surrounded by a plastic coating. A light source, called a photo diode, is

placed at the transmitting end and quickly switched on and off. The light pulses travel down

the glass cable and are detected by an optic sensor called a photo receptor on the receiving

end. Fiber optic cable is capable of transmitting data at over 100 Gbps (that‘s 100 billion bits

per second!) over several kilometers. In addition to having almost errorfree high data

transmission rates, fiber optic cable has a number of other advantages over twisted pair and

coaxial cable. Since fiber optic cable passes electrically nonconducting photons through a

glass medium, it is immune to electromagnetic interference and virtually impossible to

wiretap.

WIRELESS MEDIA

All wireless systems employ radio waves at differing frequencies. The FCC strictly

controls which frequencies are used for each particular type of service. The services covered

in this section will include terrestrial microwave transmissions, satellite transmissions, cellular

radio systems, personal communication systems, pagers, infrared transmissions, and

multichannel multipoint distribution service Terrestrial microwave transmission systems

transmit tightly focused beams of radio signals from one groundbased microwave

transmission antenna to another. Satellite microwave transmission systems are similar to

terrestrial microwave systems except that the signal travels from a ground station on earth to

a satellite and back to another ground station on earth, thus achieving much greater distances

than line-of-sight transmission. Satellites orbit the earth from four possible ranges: low earth


152

orbit (LEO), middle earth orbit (MEO), geosynchronous earth orbit (GEO), and highly

elliptical earth orbit (HEO). Two basic categories of mobile telephone systems currently

exist: cellular telephone and personal communication systems (PCS). Cellular digital packet

data (CDPD) technology supports a wireless connection for the transfer of computer data

from a mobile location to the public telephone network and the Internet. Another wireless

communication technology that has grown immensely in popularity within the last decade is

the pager. Infrared transmission is a special form of radio transmission that uses a focused

ray of light in the infrared frequency range. A broadband wireless system is one of the latest

techniques for delivering Internet services into homes and businesses. Bluetooth

transmissions will support the new short-range personal area networks, and wireless

application protocol will support cellular telephone to Internet connections.

cim manual

Documents