14. assignment topics with materials unit-i...

14. ASSIGNMENT TOPICS WITH MATERIALS

UNIT-I Fundamentals of CAD/CAM

1. THE PRODUCT CYCLE AND CAD/CAM

Diagram showing the various steps in the product cycle is presented in Figure.

The cycle is driven by customers and markets which demand the product. It is realistic to think of

these as a large collection of diverse industrial and consumer markets rather than one monolithic

market. Depending on the particular customer group, there will be differences in the way the product

cycle is activated. In some cases, the design functions are performed by the customer and the product

is manufactured by a different firm. In other cases, design and manufacturing is accomplished by the

same firm. Whatever the case, the product cycle begins with a concept, an idea for a product. This

concept is cultivated, refined, analyzed, improved, and translated into a plan for the product through

the design engineering process. The plan is documented by drafting Ii set of engineering drawings

showing how the product is made and providing a set of specifications indicating how the product

should perform.

The impact of CAD/CAM is manifest in all of the different activities in the product cycle, as

indicated in Figure. Computer-aided design and automated drafting are utilized in the

conceptualization, design, and documentation of the product. Computers are used in process planning

and scheduling to perform these functions more efficiently. Computers are used in production to

monitor and control the manufacturing operations. In quality control, computers are used to perform

inspections and performance tests on the product and its components.

As illustrated in Figure, CAD/CAM is overlaid on virtually all of the activities and functions of the

product cycle. In the design and production operations of a modem manufacturing firm, the computer

has become a pervasive, useful, and indispensable tool. It is strategically important and competitively

imperative that manufacturing firms and the people who are employed by them understand

CAD/CAM.

1. AUTOMATION AND CAD/CAM Automation is defined as the technology concerned with the application of complex mechanical,

electronic, and computer-based systems in the operation and control of production. It is the purpose

of this section to establish the relationship between CAD/CAM and automation

Production activity can be divided into four main categories:

l. Continuous-flow processes 2. Mass production of discrete products

3. Batch production 4. Job shop production

Category Description

l. Continuous-flow processes Continuous dedicated production of large amounts of bulk product. Examples include continuous chemical plants and oil refineries

2.Mass products

production of discrete Dedicated production of large quantities of one product (with perhaps limited model variations). Examples include automobiles, appliances, and engine blocks.

3. Batch production Production of medium lot sizes of the same product or component. The lots may be produced once or repeated periodically. Examples include books, clothing, and certain industrial machinery.

4. Job shop production Production of low quantities, often one of a kind, of specialized products. The products are often customized and technologically complex. Examples include prototypes, aircraft, machine tools, and other equipment.

Category Automation achievements

l. Continuous-flow processes

Flow process from beginning to end

Sensor technology available to measure important process variables

Use of sophisticated control and optimization strategies Fully computer-automated plants

2. Mass production of discrete products

Automated transfer machines Dial indexing machines

Partially and fully automated assembly lines Industrial robots for spot welding, parts handling, machine loading, spray painting, etc.

3. Batch production Numerical control (NC), direct numerical control (DNC), computer numerical control (CNC)

Adaptive control machining

4. Job shop production Numerical control, computer numerical control

2. THE DESIGN PROCESS

Before examining the several facets of computer-aided design, let us first consider the

general design process. The process of designing something is characterized by Shigley as an iterative

procedure, which consists of six identifiable steps or phases:-

l. Recognition of need 2. Definition of problem 3. Synthesis 4. Analysis and optimization 5. Evaluation 6. Presentation

Synthesis and analysis are closely related and highly interactive in the design process. A

certain component or subsystem of the overall system is conceptualized by the designer, subjected to

analysis, improved through this analysis procedure, and redesigned. The process is repeated until the

design has been optimized within the constraints imposed on the designer. The components and

subsystems are synthesized into the final overall system in a similar interactive manner.

Evaluation is concerned with measuring the design against the specifications established in

the problem definition phase. This evaluation often requires the fabrication and testing of a prototype

model to assess operating performance, quality, reliability, and other criteria. The final phase in the

design process is the presentation of the design. This includes documentation of the design by means

of drawings, material specifications, assembly lists, and so on. Essentially, the documentation requires

that a design database be created. Figure illustrates the basic steps in the design process, indicating its

iterative nature.

The general design process as defined by Shigley

3. THE APPLICATION OF COMPUTERS FOR DESIGN The various design-related tasks which are performed by a modem computer-aided design-

system can be grouped into four functional areas:

l. Geometric modeling 2. Engineering analysis 3. Design review and evaluation 4. Automated drafting

These four areas correspond to the final four phases in Shigley's general design process, illustrated

in Figure. Geometric modeling corresponds to the synthesis phase in which the physical design project

takes form on the ICG system. Engineering analysis corresponds to phase 4, dealing with analysis and

optimization. Design review and evaluation is the fifth step in the general design procedure.

Automated drafting involves a procedure for converting the design image data residing in computer

memory into a hard-copy document. It represents an important method for presentation (phase 6) of

the design. The following four sections explore each of these four CAD functions.

5. BENEFITS OF CAD l. Improved engineering productivity

2. Shorter lead times

3. Reduced engineering personnel requirements

4. Customer modifications are easier to make

5. Faster response to requests for quotations

6. Avoidance of subcontracting to meet schedules

7. Minimized transcription errors

8. Improved accuracy of design

9. In analysis, easier recognition of component interactions

10. Provides better functional analysis to reduce prototype testing

11. Assistance in preparation of documentation

l2. Designs have more standardization

l3. Better designs provided

l4. Improved productivity in tool design

l5. Better knowledge of costs provided

l6. Reduced training time for routine drafting tasks and NC part programming

l7. Fewer errors in NC part programming

l8. Provides the potential for using more existing parts and tooling

l9. Helps ensure designs are appropriate to existing manufacturing techniques

20. Saves materials and machining time by optimization algorithms

2l. Provides operational results on the status of work in progress

22. Makes the management of design personnel on projects more effective

23. Assistance in inspection of complicated parts

24. Better communication interfaces and greater understanding among engineers, designers,

drafters, management, and different project groups.

UNIT-II SURFACE MODELING

1.SURFACE MODELING Surface model is an extension of wireframe but has advantages: less ambiguous, provide realism for display with hidden lines, mesh, and shading

Surface Entities Plane surface

Surface model is an extension of wireframe but has advantages: less ambiguous, provide realism for display with hidden lines, mesh, and shading

2. Solid model

Solid Model is based on informationally complete (or spatial addressability), valid, and

unambiguous representation of objects and stores geometric data as well as topological

information of associated objects.

This representation permits automation and integration of tasks such as interference analysis,

mass property calculation, finite element modeling, CAPP (computer-aided process planning),

machine vision, and NC machining.

It is very easy to define an object with a solid model than other two previous modeling

techniques (curves and surfaces) because solid models do not need individual locations as with

wireframe models.

The above figure illustrates the difference between geometry and topology. The geometry that

defines the object is the lengths of lines, areas of surfaces, the angles between the lines, and the radius

and the center of the cylinder and the height. On the other hand, topology (sometimes called

combinatorial structure), is the connectivity and associativity of the object entities. It has to do with

the notion of neighborhood and determines the relational information between object entities. From a

user point of view, geometry is visible and topology is considered to be non-graphical relational

information that is stored in solid model databases and are not visible to users.

There are various basic building blocks, so called, primitives that can be combined in certain

boolean operations to construct complex models. They include This representation permits automation

and integration of tasks such as interference analysis, mass property calculation, finite element

modeling, CAPP (computer-aided process planning), machine vision, and NC machining. It is very

easy to define an object with a solid model than other two previous modeling techniques (curves and

surfaces) because solid models do not need individual locations as with wireframe models.

3.GEOMETRY AND TOPOLOGY

The geometry that defines the object is the lengths of lines, areas of surfaces, the angles between

the lines, and the radius and the center of the cylinder and the height. On the other hand, topology

(sometimes called combinatorial structure), is the connectivity and associativity of the object entities.

It has to do with the notion of neighborhood and determines the relational information between object

entities. From a user point of view, geometry is visible and topology is considered to be non-graphical

relational information that is stored in solid model databases and are not visible to users.

There are various basic building blocks, so called, primitives that can be combined in certain

boolean operations to construct complex models. They include

Block Cylinder Cone Sphere Wedge Torus

Constructive Solid Geometry (CSG): This is based on the topological notion that a

physical object can be divided into a set of primitives that can be combined in a certain order

following a set of rules (i.e. Boolean operations) to form the object. The basic elements are

block, cylinder, cone, sphere, wedge, and torus and building operations are Boolean

operations. The following bearing support was constructed with various primitives in a certain

sequence by CSG technique.

Sweep Representation: This is especially useful for two-and-half dimensional objects used

most frequently for extruded solids and revolved solids. This is based on sweeping of a section

along a path that may be linear, nonlinear, and hybrid operations. When the path is s

simple extrusion and when it is axisymmetric, it becomes the revolution. For nonlinear path, the

sweeping is done along a nonlinear curve in space. Cutting tool path simulation is one good

applications of this technique.The section may vary along the sweeping path. The following shows

suchan example with variable section.

4.Hermite bicubic surface

Bezier surface

UNIT-III NC CONTROL PRODUCTION SYSTEMS

1. NC PROCEDURE

To utilize numerical control in manufacturing, the following steps must be accomplished.

Process Planning. The engineering drawing of the workpart must be interpreted in terms of the

manufacturing processes to be used. this step is referred to as process planning and it is concerned

with the preparation of a route sheet. The route sheet is a listing of the sequence of operations

which must be performed on the workpart. It is called a route sheet because it also lists the

machines through which the part must be routed in order to accomplish the sequence of operations.

We assume that some of the operations will be performed on one or more NC machines.

Part programming. A part programmer plans the process for the portions of the job to be

accomplished by NC. Part programmers are knowledgeable about the machining process and they

have been trained to program for numerical control. They are responsible for planning the

sequence of machining steps to be performed by NC and to document these in a special format.

There are two ways to program for NC:

Manual part programming

Computer-assisted part programming

In manual programming, the machining instructions are prepared on a form called a part

program manuscript. The manuscript is a listing of the relative cutter/work piece positions which

must be followed to machine the part. In computer-assisted part programming, much of the tedious

computational work required in manual part programming is transferred to the computer. This is

especially appropriate for complex work piece geometries and jobs with many machining steps.

Use of the computer in thesea). Attendance & other issues

NC procedure


l. Process Planning. The engineering drawing of the workpart must be interpreted in terms of

the manufacturing processes to be used. this step is referred to as process planning and it is concerned

with the preparation of a route sheet. The route sheet is a listing of the sequence of operations which

must be performed on the work part. It is called a route sheet because it also lists the machines

through which the part must be routed in order to accomplish the sequence of operations. We assume

that some of the operations will be performed on one or more NC machines.

Part programming. A part programmer plans the process for the portions of the job to be





Manual part programming Computer-assisted part programming


program manuscript. The manuscript is a listing of the relative cutter/work piece positions which must

be followed to machine the part. In computer-assisted part programming, much of the tedious


especially appropriate for complex work piece geometries and jobs with many machining steps. Use

of the computer in these situations results in significant savings in part programming time.

Tape preparation. A punched tape is prepared from the part

manual part programming, the punched tape is prepared directly from the part program manuscript on

a typewriter like device equipped with tape punching capability. In computer-assisted part

programming, the computer interprets the list of part programming instructions, performs the

necessary calculations to convert this into a detailed set of machine tool motion commands, and then

controls a tape punch device to prepare the tape for the specific NC machine.

Tape verification. After the punched tape has been prepared, a method isusually provided for

checking the accuracy of the tape. Some times the tape is checked by running it through a computer

program which plots the various tool movements (or table movements) on paper. In this way, major

errors in the tape can be discovered. The "acid test" of the tape involves trying it out on the machine

tool to make the part. A foam or plastic material is sometimes used for this tryout. Programming

errors are not uncommon, and it may require about three attempts before the tape is correct and

ready to use.

Production. The final step in the NC procedure to use the NC tape in production. This involves

ordering the raw workparts specifying and preparing the tooling and any special fixturing that may be

required, and setting up The NC machine tool for the job. The machine tool operator's function during

production is to load the raw workpart in the machine and establish the starting position of the cutting

tool relative to the workpiece. The NC system then takes over and machines the part according to the

instructions on tape. When the part is completed, the operator removes it from the machine and loads

the next part.

2. Fixed zero and floating zero

The programmer must determine the position of the tool relative to the origin (zero point) of

the coordinate system. NC machines have either of two methods for specifying the zero point. The

first possibility is for the machine to have a fixed zero. In this case, the origin is always located at the

same position on the machine. Usually, that position is the southwest comer (lower left-hand comer)of

the table and all tool locations will be defined by positive x and y coordinates.

The second and more common feature on modern NC machines allows the machine operator to set the

zero point at any position on the machine table. This feature is called floating zero. The part

programmer is the one who decides where the zero point

should be located. The decision is based on part programming convenience. For example, the

work part may be symmetrical and the zero point should be established at the center of symmetry.

Absolute versus incremental positioning


Another option sometimes available to the part programmer is to use either an absolute

system of tool positioning or an incremental system. Absolute positioning means that the tool

locations are always defined in relation to the zero point. If a hole is to be drilled at a spot that is 8 in.

above the x axis and 6in. to the right of the y axis, the coordinate location of the bole would be

specified as x = +6.OOO and y = +8.OOO. By contrast, incremental positioning means that the next

tool location must be defined with reference to the previous tool location. If in our drilling example,

suppose that the previous hole had been drilled at an absolute position of x = +4.OOO and y =

+5.OOO. Accordingly, the incremental position instructions would be specified as x = +2.OOO and y

= +3.OOO in order to move the drill to the desired spot. Figure illustrates the difference between

absolute and incremental positioning.

NC MOTION CONTROL SYSTEMS In order to accomplish the machining process, the cutting tool and workpiece must be moved

relative to each other. In NC, there are three basic types of motion control systems.

Absolute positioning and incremental positioning system NC motion control systems.

3.Absolute versus incremental positioning






The second and more common feature on modern NC machines allows the machine operator

to set the zero point at any position on the machine table. This feature is called floating zero. The part

programmer is the one who decides where the zero point should be located. The decision is based on

part programming convenience. For example, the work part may be symmetrical and the zero point

should be established at the center of symmetry.













NC MOTION CONTROL SYSTEMS In order to accomplish the machining process, the cutting tool and workpiece must be moved

relative to each other. In NC, there are three basic types of motion control systems: -

l. Point-to-point

2. Straight cut

3. Contouring

Point-to-point NC Point-to-point (PTP) is also sometimes called a positioning system. In PTP, the objective of

the machine tool control system is to move the cutting tool to a predefined location. The speed or path

by which this movement is accomplished is not import in point-to-point NC. Once the tool reaches the

desired location, the machining operation is performed at that position.

NC drill presses are a good example of PTP systems. The spindle must first be positioned at a

particular location on the work piece. This is done under PTP control. Then the drilling of the hole is

performed at the location, and so forth. Since no cutting is performed between holes, there is no need

for controlling the relative motion of the tool and work piece between hole locations. Figure illustrates

the point-to-point type of control.

Positioning systems are the simplest machine tool control systems and are therefore the least

expensive of the three types. However, for certain processes, such as drilling operations and spot

welding, PIP is perfectly suited to the task and any higher level of control would be unnecessary.

Straight-cut NC Straight-cut control systems are capable of moving the cutting tool parallel to one of the major axes at

a controlled rate suitable for machining. It is therefore appropriate for performing milling operations

to fabricate workpieces of rectangular configurations. With this type of NC system it is not possible to

combine movements in more than a Single axis direction. Therefore, angular cuts on the workpiece

would not be possible. An example of a straight-cut operation is shown in Figure

Straight-cut system

Contouring NC Contouring is the most complex, the most flexible, and the most expensive type of machine

tool control. It is capable of performing both PTP and straight-cut operations. In addition, the

distinguishing feature of contouring NC systems is their capacity for simultaneous control of more

than one axis movement of the machine tool. The path of the cutter is continuously controlled to

generate the desired geometry of the workpiece. For this reason, contouring systems are also called

continuous-path NC systems.

Straight or plane surfaces at any orientation, circular paths, conical shapes, or most any other

mathematically definable form are possible under contouring control. Figure illustrates the versatility

of continuous path NC. Milling and turning operations are common examples of the use of contouring

control. In order to machine a curved path in a numerical control contouring system, the direction of

the feed rate must continuously be changed so as to follow the path. This is accomplished by breaking

the curved path into very short straight-line segments that approximate the curve. Then the tool is

commanded to machine each segment in succession

4.APPLICATIONS OF NUMERICAL CONTROL

Numerical control systems are widely used in industry today, especially in the metalworking

industry. By far the most common application of NC is for metal cutting machine tools. Within this

category, numerically controlled equipment has been built to perform virtually the entire range of

material removal processes, including:

Milling, Drilling and related processes Boring, Turning, Grinding, Sawing Within the machining category, NC machine tools are appropriate for certain jobs and

inappropriate for others. Following are the general characteristics of production jobs in metal

machining for which numerical control would be most appropriate:

l. Parts are processed frequently and in small lot sizes.

2. The part geometry is complex.

3. Many operations must be performed on the part in its processing.

4. Much metal needs to be removed.

5. Engineering design changes are likely.

6. Close tolerances must be held on the workpart.

7. It is an expensive part where mistakes in processing would be costly.

8. The parts require lOO% inspection

It has been estimated that most manufactured parts are produced in lot sizes of 5O or fewer.

Small-lot and batch production jobs represent the ideal situations for the application of NC. This is

made possible by the capability to program the NC machine and to save that program for subsequent

use in future orders. If the NC programs are long and complicated (complex part geometry, many

operations, much metal removed), this makes NC all the more appropriate when compared to manual

methods of production. If engineering design changes or shifts in the production schedule are likely,

the use of tape control provides the flexibility needed to adapt to these changes. Finally, if quality and

inspection are important issues (close tolerances, high part cost, lOO% inspection required), NC

would be most suitable, owing to its high accuracy and repeatability.

In order to justify that a job be processed by numerical control methods, it is not necessary that

the job possess every one of these attributes. However, the more of these characteristics that are

present, the more likely it is that the part is a good candidate for NC.

In addition to metal machining, numerical control has been applied to a variety of other

operations. The following, although not a complete list, will give the reader an idea of the wide range

of potential applications of NC:

Pressworking machine tools Welding machines Inspection machines Automatic drafting Assembly

machines

Tube bending Flame cutting Plasma arc cutting

Laser beam processes Automated knitting machines Cloth cutting

Automatic riveting Wire-wrap machines

Advantages of NC Following are the advantages of numerical control when it is utilized in the type of

production jobs described.

l. Reduced nonproductive time. Numerical control has little or no effect on the basic metal,

cutting (or other manufacturing) process. However; NC can increase the proportion of time the

machine is engaged in the actual process. It accomplishes this by means of fewer setups, less time in

setting up, reduced work piece handling time, automatic tool changes on some machines, and so on.

In a University of Michigan survey reported by Smith and Evans, a comparison was made

between the machining cycle times for conventional machine tools versus the cycle times for NC

machines. NC cycle times, as a percentage of their conventional counterparts, ranged from 35% for

five-axis machining centers to 65% for presswork punching. The advantage for numerical control

tends to increase with the more complex processes.

Reduced fixturing. NC requires fixtures which are simpler and less costly to fabricate

because the positioning is done by the NC tape rather than the jig or fixture

Reduced manufacturing lead time. Because jobs can be set up more quickly with NC and

fewer setups are generally required with NC, the lead time to deliver a job to the customer is reduced.

Greater manufacturing flexibility. With numerical control it is less difficult to adapt to

engineering design changes alterations of the production schedule, changeovers in jobs for rush

orders, and so on.

Improved quality control. NC is ideal for complicated workparts where the chances of human

mistakes are high. Numerical control produces parts with greater accuracy, reduced scrap, and lower

inspection requirements.

Reduced inventory. Owing to fewer setups and shorter lead times with numerical control, the

amount of inventory carried by the company is reduced.

Reduced floor space requirements. Since one NC machining center can often accomplish the

production of several conventional machines, the amount of floor space required in an NC shop is

usually less than in a conventional shop.

Disadvantages of NC Along with the advantages of NC, there are several features about NC which must be

considered disadvantages:

Higher investment cost. Numerical control machine tools represent a more sophisticated and

complex technology. This technology costs more to buy than its non-NC counterpart. The higher cost

requires manufacturing managements to use these machines more aggressively than ordinary

equipment. High machine utilizationis essential on order to get reasonable returns on investment.

Machine shops must operate their NC machines two or three sifts per day to achieve this high machine

utilization.

Higher maintenance cost. Because NC is a more complex technology and because NC

machines are used harder, the maintenance problem becomes more acute. Although the reliability of

NC systems has been improved over the years, maintenance costs for NC machines will generally be

higher than for conventional machine tools.

Finding and/or training NC personnel. Certain aspects of numerical control shop

operations require a higher skill level than conventional operations. Part programmers and NC

maintenance personnel are two skill areas where available personnel are in short supply. The problems

of finding, hiring, and training these people must be considered a disadvantage to the NC shop

5.NC PART PROGRAMMING

Following is a list of the different types of words in the formation of a block. Not very NC

machine uses all the words. Also, the manner in which the words are expressed will differ between

machines. By convention, the words in a block are given in the following order:

SEQUENCE NUMBER (n-words): This is used to identify the block. PREPARATORY WORD (g-words): This word is used to prepare the controller for instructions that

are to follow. For example, the word gO2 is used to prepare the C controller unit for circular

interpolation along an arc in the clockwise direction. The preparatory word l& needed S9 that the

controller can correctly interpret the data that follow it in the block.

COORDINATES (x-, y-, and z-words): These give the coordinate positions of the tool. In a two-axis

system, only two of the words would be used. In a four- or five- axis machine, additional a-words and

V or b-words would specify the angular positions.

Although different NC systems use different formats for expressing a coordinate, we will

adopt the convention of expressing it in the familiar decimal form: For example, x + 7.235 ory-O.5ao.

Some formats do not use the decimal point in writing the coordinate. The + sign to define a positive

coordinate location is optional. The negative sign is, of course, mandatory.

FEED RATE (f-word): This specifies the feed in a machining operation. Units are inches per minute

(ipm) by convention.

CUTTING SPEED (s-word): This specifies the cutting speed of the process, the rate at which the

spindle rotates.

TOOL SELECTION (t-word): This word would be needed only for machines with a tool turret or

automatic tool changer. The t-word specifies which tool is to be used in the operation. For example,

tO5 might be the designation of a l/2-in. drill bit in turret position 5 on an NC turret drill.

MSCELLANEOUS FUNCTION (m-word): The m-word is used to specify certain miscellaneous or auxiliary functions which may be available on the machine tool.

The work part of Example was relatively simple. It was a suitable application for manual

programming. Most parts machined on NC systems are considerably more complex. In the more

complicated point-to-point jobs and in contouring applications, manual part programming becomes an

extremely tedious task and subject to errors. In these instances it is much more appropriate to employ

the high-speed digital computer to assist in the part programming process. Many part programming

language systems have been developed to perform automatically cost of the calculations which the

programmer would otherwise be forced to do. This saves time and results in a more accurate and more

efficient part program.

UNIT-IV GROUP TECHNOLOGY

1. Group technology

Group technology (abbreviated GT) 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.

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.

Advantage derived from grouping workparts into families can be explained with reference to

Figures.

Figure shows a process-type layout for batch production in a machine shop. 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 workpiece 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, long

manufacturing lead times, and high cost. Figure shows a production shop of supposedly equivalent

capacity, but with the machines arranged into cells. Each cell is organized to specialize in the

manufacture of a particular part family.

Group technology (abbreviated GT) 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.

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.

Advantage derived from grouping work parts into families can be explained with reference to

Figures. Figure shows a process-type layout for batch production in a machine shop. 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 workpiece 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, long

manufacturing lead times, and high cost. Figure shows a production shop of supposedly equivalent

capacity, but with the machines arranged into cells. Each cell is organized to specialize in the

manufacture of a particular part family.

Group technology layout:

The set of similar components can be called as a part family. Since all family members require similar

processes, a machine cell can be built to manufacture the family. This makes production planning and

control much easier because only similar components are considered for each cell. Such a cell-

oriented layout is called a group-technology layout or cellular layout.

Advantages are gained in group-technology layout

Reduced workpiece handling

Lower setup times.

Less in-process 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.

The three methods for grouping parts into families are:

1.Visual inspection method.

2.Production flow analysis (PFA).

3.Parts classification and coding system.

Visual inspection method:

It is the least sophisticated and least expensive method. It involves the classification of parts into

families by looking at either the physical parts or photographs and arranging them into similar

groupings.

This method is generally considered to be the least accurate of the three.

Production flow analysis (PFA):

The second method, production flow analysis, was developed by J. L.

Burbidge. PFA is a method of identifying part families and associated machine tool groupings by

analyzing the route sheets for parts produced in a given shop. It groups together the parts that have

similar operation sequences and machine routings.

The disadvantage of PFA is that it accepts the validity of existing route sheets, with no

consideration given to whether these process plans are logical or consistent. The production flow

analysis approach does not seem to be used much at all in the United States.

Parts 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 a code number. This classification and coding may be carried out on the entire list of active

parts of the firm, or a sampling process may be used to establish the part families.

Many parts classification and coding systems have been developed throughout the world, and

there are several commercially available packages being sold to industrial concerns.

Design and Manufacturing Part Attributes Typically Included in a Group Technology

Classification System

Part design attributes

Basic external shape Major dimensions

Basic internal shape Minor dimensions

Length/diameter ratio Tolerances

Material type Surface finish Part function

Part manufacturing attributes Major process Operation sequence

Minor operations Production time

Major dimensions Batch size

Length/diameter ratio Annual production

Surface finish Fixtures needed

Machine tool Cutting tools

Parts classification and coding systems divide themselves into one of three general categories: l. Systems based on part design attributes 2.Systems based on part manufacturing attributes 3.Systems based on both design and manufacturing attributes

Coding system structure

1.Hierarchical structure 2.Chain-type structure 3.Hybrid structure 2. THE OPITZ CLASSIFICATION SYSTEM The Opitz coding system uses the following digit sequence:

l2345 6789 ABCD

The basic code consists of nine digits, which can be extended by adding four more digits.

The first nine digits are intended to convey both design and manufacturing data. The

general interpretation of the nine digits is indicated in Figure. The first five s, l2345, are called

the "form code" and describe the primary design attributes of the part. The next four digits,

It indicates some of the attributes that would be of use to manufacturing (dimensions, work

material, starting raw workpiece shape and accuracy).

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.

3.THE MICLASS SYSTEM

MICLASS stands for Metal Institute Classification System and was developed by TNO, the

Netherlands Organization for Applied Scientific Research. It was started in Europe about five years

before being introduced in the United States in l974. Today, it is marketed in the United States by the

Organization for Industrial Research in Waltham, Massachussets. 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 drawings 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 from l2 to 3O digits. The first l2 digits are a universal

code that can be applied to any part. Up to l8 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 included in the l8 supplementary digits.

The work part attributes coded in the first l2 digits of the MICLASS number are as follows:

lst digit Main shape

2nd and 3rd digits Shape elements

4th digit Position of shape elements







Standardization of engineering drawings

Retrieval of drawings 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 from l2 to 3O digits. The first l2 digits are a

universal code that can be applied to any part. Up to l8 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


The work part attributes coded in the first l2 digits of the MICLASS number are as follows:

lst digit Main shape

2nd and 3rd digits Shape elements

4th digit Position of shape elements

5th and 6th digits Main dimensions

7th digit Dimension ratio

8th digit Auxiliary dimension

9th and lOth digits Tolerance codes

llth and l2th digits Material codes

The CODE system

The CODE system is a parts classification and coding system developed and marketed by

Manufacturing Data Systems, Inc. (MDSI), of Aim 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.

The CODE number has eight digits. For each digit there are l6 possible values (zero through

9 and A through F) which are used to describe the part's 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 the first digit, but

these remaining digits form a chain-type structure. Hence the CODE system possesses a hybrid

structure.

Benefits of group technology

Product design.

Tooling and setups.

Materials handling.

Production and inventory control.

Employee satisfaction.

Process planning procedures.

4. GENERATIVE PROCESS PLANNING SYSTEMS

RETRIEVAL - TYPE PROCESS PLANNING SYSTEMS

Retrieval-type CAPP systems use parts classification and coding and group technology as a

foundation. In this approach, the parts produced in the plant aregrouped into part families,

distinguished according to their manufacturing characteristics. For each part family, a standard

process plan is established. The standard process plan is stored in computer files and then retrieved for

new workparts which belong to that family. Some form of parts classification and coding system is

required to organize the computer files and to permit efficient retrieval of the appropriate process plan

for a new workpart. For some new parts, editing of the existing process plan may be required. This is

done when the manufacturing requirements of the new part are slightly different from the standard.

The machine routing may be the same for the new part, but the specific operations required at each

machine may be different. The complete process plan must document the operations as well as the

sequence of machines through which the part must be routed. Because of the alterations that are made

in the retrieved process plan, these CAPP systems are sometimes also called by the name' 'variant

system."

Figure will help to explain the procedure used in a retrieval process planning system. The

user would initiate the procedure by entering the part code number at a computer terminal. The CAPP

program then searches the part family matrix file to determine if a match exists. If the file contains an

identical code number, the standard machine routing and operation sequence are retrieved from the

respective computer files for display to the user. The standard process plan is examined by the user to

permit any necessary editing of the plan to make it compatible with the new part design. After editing,

the process plan formatter prepares the paper document in the proper form.

If an exact match cannot be found between the code numbers in the computer file and the

code number for the new part, the user may search the machine routing file and the operation

sequence file for similar parts that could be used to develop the plan for the new part. Once the

process plan for a new part code number has been entered, it becomes the standard process for future

parts of the same classification.

GENERATIVE PROCESS PLANNING SYSTEMS

Information flow in a retrieval-type computer-aided process planning system.

Generative process planning involves the use of the computer to create an individual process

plan from scratch, automatically and without human assistance. The computer would employ a set of

algorithms to progress through the various technical and logical decisions toward a final plan for

manufacturing. Inputs to the ~ tern would include a comprehensive description of the work part. This

may involve the use of some form of part code number to summarize the work part data, but does not

involve the retrieval of existing standard plans. Instead, the general CAPP system synthesizes the

design of the optimum process sequence, based an analysis of part geometry, material, and other

factors which would influence manufacturing decisions.

In the ideal generative process planning package, any part design could presented to the

system for creation of the optimal plan. In practice, cu generative- type systems are far from universal

in their applicability. They ter fall short of a truly generative capability, and they are developed for a

some limited range of manufacturing processes.

We will illustrate the generative process planning approach by means system called

GENPLAN developed at Lockheed-Georgia Company

5. MATERIAL REQUIREMENTS PLANNING:

Material Requirements Planning (MRP) is a computational technique that converts the master

schedule for end products into a detailed schedule for the raw materials & components used in the end

products. The detailed schedule identifies the quantities of each raw material & component item. It

also indicates when each item must be ordered & delivered to meet the master schedule for final

products. MRP is often thought of as a method of inventory control. It is both an effective tool for

minimizing unnecessary inventory investment & a useful method in production scheduling &

purchasing of materials.

The MRP processor operates on data contained in the MPS, the BOM file, and the inventory

record file. The master schedule specifies the period-by period list of final products required. The

BOM define what material and components are needed for each Product and inventory record files

gives the current and future inventory status of each product, component, and material. The MRP

processor computers how many of each component and raw material

Several complicating factors must be considered during the MRP computations. First the

quantities of component and subassemblies listed in the solution of Example 25.1 do not account for

any of those items that may already be stocked in inventory or are expected to be received as future

order. Accordingly, the computed quantities must be adjusted for any inventories on hand or on order,

a procedure called netting. For each time bucket, net requirements = gross requirements less on hand

inventories and less quantities on order.

Second, quantities of common use items must be combined during parts explosion to

determine the total quantities required for each component and raw material in the schedule. Common

use items are raw materials and components that are used on more than one product. MRP collects

these common use items from different products to achieve economics in ordering the raw materials

and producing the components.

Third, lead times for each item must be taken into account, The lead time for a job is the time

that must be allowed to complete the job from start to finish. There are two kinds of lead times in

MRP: ordering lead timed and manufacturing lead times. Ordering lead time for an item is the time

required from initiation of the purchase requisition to receipt of the item from the vendor. If the item is

raw material that is stocked by the vendor, the ordering lead time should be relatively short, perhaps a

few days or a few weeks. If the items is fabricated, the lead time may be substantial, perhaps several

form order release to completion, once the raw material for the item are available. The scheduled

delivery of end product must be translated into time-phased requirements for components and

materials by factoring in the ordering and manufacturing lead time.

UNIT-V FLEXIBLE MANUFACTURING SYSTEM

1.Flexible manufacturing systems

Group of processing stations inter connected by means of a automated material handling and storage

system, and controlled by an integrated computer system.

The guided vehicles are used as the materials handling system in the FMS. The vehicles deliver

work from the staging area (where work is placed on pallet fixtures, usually manually) to the

individual workstations in the system. The vehicles also move work between stations in the

manufacturing system. At a workstation, the work is transferred from the vehicle platform into the work

area of the station (usually, the table of a machine tool) for processing. At the completion of processing

by that station a vehicle returns to pick up the work and transport it to the next area. AGV systems

provide a versatile material handling system to complement the flexibility of the FMS operation.

Hardware components

Workstations - CNC machines in a machining type system

Material handling system - means by which parts are moved between stations

Central control computer - to coordinate the activities of the components so as to achieve a

smooth overall operation of the system

Software and control functions

Human labor

(a) in-line Lay out Key: Aut = automated station;

L/UL = load/unload station;

Insp = inspection station;

AGV = automated guided vehicle; AGVS = automated guided vehicle system

(b) Ladder layout

Key: Aut = automated station;

L/UL = load/unload station;

Insp = inspection station;

AGV = automated guided vehicle; AGVS = automated guided vehicle system (c) open field

Key: Aut = automated station; L/UL = load/unload station;

2. INSPECTION

Inspection has become an essential part of any manufacturing system. It is the means of

rejecting nonconformities and assuring good quality products. The advent of technologically updated

inspection equipment helped to overcome the problems associated with traditional approaches.

Traditional approach used labor -intensive methods that resulted in the increase of manufacturing lead

time and production cost. Moreover, there is a significant delay in detecting an out of control limit.

Thus the products that are not conforming to the specified standards accrue to the additional cost of

scrap and rework.

New approach to quality control laid down conditions under which inspection should be carried out.

The new approach includes :

(i) Manual inspection method surrogated by 100% automated inspection.

(ii) Offline inspection performed later is replaced with online sensor systems to accomplish inspection

during or immediately after the manufacturing process.

(iii) Feedback control of the manufacturing operation in which process variable that determines

product quality are monitored rather than the product itself.

(iv) Statistical process control is ensured using software tools to track and analyze the sensor

measurement over time.

(v) Advanced inspection and sensor technologies, interfaced with computer based systems to automate

the operations of the sensor systems

The term inspection can be defined as the activity of examining the products, its components,

sub-assemblies, or materials out of which it is made, and to determine whether they adhere to design

specifications. The design specifications are prescribed by the product designer.

Inspection vs Testing

Quality control (QC) utilizes both inspection and testing procedures that are equally important

functional aspects of product whereas inspection is used to assess the quality and its design

specifications. The item tested in the QC testing is observed during actual operation or under

conditions that might be present during operation. For example, to know whether the product is

functioning properly, it is tested, by running it for a certain period of time.

Sometimes, testing procedures are of destructive nature, in which limited numbers of items are

sacrificed to ensure the quality of majority of items. Efforts are made to devise methods known as

nondestructive testing (NDT) and nondestructive evaluation (NDE) to save the expenses incurred

during destructive testing.

Automated inspection

In present scenario, manual inspection is largely replaced by automated inspection as errors are

reduced to great extent by automation of the process. Economic justification of an automated

inspection system depends on whether the savings in labour cost and improvement in accuracy

will be more than the investment and or development costs of the system.

Automated inspection is defined as the automation of one or more steps involved in the

inspection procedure. Automated or semi-automated inspection can be implemented in the

number of alternative ways.

Automated presentation of parts by an automatic handling system with manual examination

and decision steps.

Machine with manual loading parts into the machine doing, automated examination and

decision making.

Completely automated inspection system in which parts presentation, examination and

decisions are performed automatically.

3.Timing of Inspection

An important consideration in quality control is the determination of timings of the inspection

procedure. Three different options can be identified which are :

(a) off-line inspection,

(b) on-line/in-process, and

(c) on-line/post process inspection.

Off-line Inspection Methods

In off-line inspection, the inspection equipment is usually dedicated and does not make any physical

contact with machine tools. There is always a time delay between production and inspection. Manual

inspection is common that tend to promote the use of offline inspection that include:

(i) variability of the process is well within the design tolerance,

(ii) processing conditions are stable and the risk of significant deviation in the process is small, and

(iii) cost incurred during inspection is high in comparison to the cost of few defective parts.

The disadvantage of offline inspection is that the parts have already been made by the time

poor quality is detected. Sometimes by default a defective part may not be included into the

sample. A coordinate measuring machine (CMM) is an example of off-line inspection. CMM is

discussed in detail in the next section.

On-line/In-process and On-line/Post-process Inspection Methods

If the task of inspection is done as the parts are manufactured, then it is called as online inspection.

There are two variations of on-line inspection. If the inspection is performed during the manufacturing

operation, it is called on-line/in-process inspection. If the inspection is performed immediately

following the production process, it is called on-line/post-process inspection

4.CONSTRUCTIONAL DETAILS OF CMM

The construction of CMM can best be described with the help of its two basic components:

(1) Probe and (2) Mechanical structure.

Probe

The contact probe is an important component of CMM. The probe is fastened to mechanical

structure that allows movement of probe relative to the part. When contact has been made with part

surface during measurement. The tip of the probe is made of ruby ball. Ruby is a form of Corundum

(aluminum oxide). High hardness for wear resistance and low density for minimum inertia are the

required characteristics for the application of ruby in probe. Probe is of two types (1) single tip , and

(2) multiple tips .

Touch trigger probes are most widely used probes. The probe actuates when the contact is

made with part surface.

The various triggering mechanism, which are used commercially are discussed as follows.

(i) The trigger is based on the principle that, when the tip of the probe is deflected from neutral

position then the highly sensitive electrical contact switch starts emitting signal.

(ii) The trigger actuates when there is an electrical contact between probe and metallic part

surface.

(iii) The trigger uses a piezoelectric sensor that generates a signal based on tension or

compression loading of the probe.

As contact exists between the probe and the surface of the object then with the help of

displacement transducer the coordinate position of the probe are accurately measured. Various

displacement transducers such as optical scales, rotary encoding, and magnetic scales etc are used in

CMM. Probe

On the basis of operating and controlling of CMM, it can be classified in the four following ways :

(i) manual drive,

(ii) manual drive with computer-assisted data processing,

(iii) motor drive with computer-assisted data processing, and

(iv) DCC with computer-assisted data processing.

contact with the part and the measurements are recorded in manual drive CMM. The three orthogonal

slides are designed to be nearly frictionless to permit the probe to be free floating in the x, y, and z-

directions. A digital readout provides the measurements that the operator can record either manually or

with paper printout. Only operator is allowed to carry out calculations on the data that includes the

enumeration of the center and hole diameter.

Data processing and computational capability for performing the calculations that are required

to evaluate a given part feature are provided by a CMM with manual drive CMM with computer-

assisted data processing. The different types of data processing and computations are ranging from

simple conversions between US customary units and metric to more complicated geometry

calculations, such as determining the angle between two planes. The probe is free floating and permits

the operator to bring it into contact with the desired part surfaces.

Electric motors are used in a motor driven CMM with the computer-assisted data processing to

drive the probe along the machine axes under the operator control. The motion is controlled by

joystick or similar devices. The collisions between the probe and the part are reduced by low-power

stepping motor and friction clutches.

CMM with direct computer control (DCC) operates just like a CNC machine tool. It is power

driven and the movements of the coordinate axes are controlled by a dedicated computer under

program control. Various data processing is performed by the computer and it also keeps record of the

measurements made during inspection. DCC CMM requires a part programming facility.

5.INTRODUCTION TO COMPUTER INTEGRATED MANUFACTURING (CIM) 1. Flexible Manufacturing System (FMS)

2. Variable Mission Mfg. (VMM)

3. Computerized Mfg. System (CMS)

Four Plan Concept CIM System discussed:

Computer Numerical Control (CNC)

Direct Numerical Control (DNC)

Computer Process Control

Computer Integrated Production Management

Automated Inspection Methods

Industrial Robots etc.

A CIM System consists of the following basic components:

Machine tools and related equipment

Material Handling System (MHS)

Computer Control System

Human factor/labor

15. Tutorial topics and Questions 16. Unit wise-Question bank

UNIT-I Two marks of questions with answers

1. Define Product cycle.

Two marks Question and Answer Product cycle is the process of managing the entire

lifecycle of a product from starting, through design and manufacture, to repair and removal of

manufactured products.

2. What is conceptualization in design process?

A Concept Study is the stage of project planning that includes developing ideas and

taking into account the all features of executing those ideas. This stage of a project is done to

reduce the likelihood of assess risks, error and evaluate the potential success of the planned

project.

3. Describe Computer Aided Design.

CAD is the function of computer systems to support in the creation, modification,

analysis, or optimization of a design. CAD software is used to raise the productivity of the

designer, progress the quality of design, progress communications through documentation, and

to generate a database for manufacturing.

4.

Rendering is the making of a two dimensional image from a three dimensional model

by means of computer programs. A picture file has objects in a strictly defined data structure; it

would have information of geometry, lighting, viewpoint, texture, and shading as a description

of the scene.

5. Write down the eccentricity value for ellipse, parabola and hyperbola.

The value of eccentricity less than one is ellipses, those with eccentricity equal to one

are parabolas, and those with eccentricity greater than one is hyperbolas.

Three marks of questions with answers

1. List our the tasks for the managers in effective management:

The following six tasks for the managers of CIM:

1. Develop a business model to understand the problem environment

2. Develop a functional model for the processes, functions, and activities to describe

both "as is" and "to be".

3. Develop an information model that identifies system interfaces, information

exchange patterns, database requirements and applicable technologies.

4. Develop a network model to identify communication and networking requirements

5. Develop an organizational model to investigate the implications of integrating the

various islands of automation on the existing organization structure and culture, and how to

safeguard against detrimental effects.

6. Finally, develop the implementation plan which should take into account special

features of the business and operations.

2. Explain Automation?

Automation is defined as the technology concerned with the application of complex

mechanical, electronic, and computer-based systems in the operation and control of production. It is

the purpose of this section to establish the relationship between

CAD/CAM and automation

Production activity can be divided into four main categories:

l. Continuous-flow processes 2. Mass production of discrete products

3. Batch production 4. Job shop production

Category Description

l. Continuous-flow processes Continuous dedicated production of large amounts of bulk product. Examples include continuous chemical plants and oil refineries

2.Mass products

production of discrete Dedicated production of large quantities of one product (with perhaps limited model variations). Examples include automobiles, appliances, and engine blocks.

3. Batch production Production of medium lot sizes of the same product or component. The lots may be produced once or repeated periodically. Examples include books, clothing, and certain industrial machinery.

4. Job shop production Production of low quantities, often one of a kind, of specialized products. The products are often customized and technologically complex. Examples include prototypes, aircraft, machine tools, and other equipment.

3. What are steps in the design process ?

Before examining the several facets of computer-aided design, let us first consider the

general design process. The process of designing something is characterized by Shigley as an iterative

procedure, which consists of six identifiable steps or phases:-

Recognition of need Definition of problem Synthesis Analysis and optimization Evaluation Presentation

Synthesis and analysis are closely related and highly interactive in the design process. A

certain component or subsystem of the overall system is conceptualized by the designer, subjected to

analysis, improved through this analysis procedure, and redesigned. The process is repeated until the

design has been optimized within the constraints imposed on the designer. The components and

subsystems are synthesized into the final overall system in a similar interactive manner.

Evaluation is concerned with measuring the design against the specifications established in

the problem definition phase. This evaluation often requires the fabrication and testing of a prototype

model to assess operating performance, quality, reliability, and other criteria. The final phase in the

design process is the presentation of the design. This includes documentation of the design by means

of drawings, material specifications, assembly lists, and so on. Essentially, the documentation requires

that a design database be created. Figure illustrates the basic steps in the design process, indicating its

iterative nature.

4. Benfits of CAD?

l. Improved engineering productivity

2. Shorter lead times

3. Reduced engineering personnel requirements

4. Customer modifications are easier to make

5. Faster response to requests for quotations

6. Avoidance of subcontracting to meet schedules

7. Minimized transcription errors

8. Improved accuracy of design

9. In analysis, easier recognition of component interactions

10. Provides better functional analysis to reduce prototype testing

5. Give short notes on stroke writing and raster scan system?

The stroke-writing system

The stroke-writing system uses an electron beam which operates like a pencil to create

a line image on the CRT screen. The image is constructed out of a sequence of straight-line

segments. Each line segment is drawn on the screen by directing the beam to move from one

point on the screen to the next, where each point is defined by its x and y coordinates. The

process is portrayed in Figure . Although the procedure results in images composed of only

straight lines, smooth curves can be approximated by making the connecting line segments

short enough.

Raster scan system.

In the raster scan approach, the viewing screen is divided into a large number of

discrete phosphor picture elements, called pixels. The matrix of pixels constitutes the raster.

The number of separate pixels in the raster display might typically range from 256 ×256 (a

total of over 65,(OO) to lO24 × lO24 (a total of over l,OOO,OOO points). Each pixel on the

screen can be made to glow with a different brightness. Color screens provide for the pixels to

have different colors as well as brightness. During operation, an electron beam creates the

image by sweeping along a horizontal line on the screen from left to right and energizing the

pixels in that line during the sweep. When the sweep of one line is completed, the electron

beam moves to the next line below and proceeds in a fixed pattern as indicated in Figure. After

sweeping the entire screen the process is repeated at a rate of 3O to 6O entire scans of the

screen per second

Five marks of questions with answers

1. Explain Manufacturing support applications.

These are the indirect applications in which the computer is used in support of the production operations in the plant, but there is no direct interface between the computer and the manufacturing process. The distinction between the two categories is fundamental to an understanding of computer-aided manufacturing. It seems appropriate to elaborate on our brief definitions of the two types. Computer monitoring and control can be separated into monitoring applications and control applications. Computer process monitoring involves a direct computer interface with the manufacturing process for the purpose of observing the process and associated equipment and collecting data from the process. The computer is not used to control the operation directly. The control of the process remains in the hands of human operators, who may be guided by the information compiled by the computer. Computer process control goes one step further than monitoring by not only observing the process but also controlling it based on the observations. The distinction between monitoring and control is displayed in Figure. With computer monitoring the flow of data between the process and the computer is in one direction only, from the process to the computer. In control, the computer interface allows for a two-way flow of data. Signals are transmitted from the process to the computer, just as in the case of computer monitoring. In addition, the computer issues command signals directly to the manufacturing process based on control algorithms contained in its software. In addition to the applications involving a direct computer-process interface for the purpose of process monitoring and control, computer-aided manufacturing also includes indirect applications in which the computer serves a support role in the manufacturing operations of the plant. In these applications, the computer is not linked directly to the manufacturing process.

2. Explain the steps in Design Process

Before examining the several facets of computer-aided design, let us first consider the general design process. The process of designing something is characterized by Shigley as an iterative procedure, which consists of six identifiable steps or phases:- l. Recognition of need 2. Definition of problem 3. Synthesis

4. Analysis and optimization 5. Evaluation 6. Presentation

Recognition of need involves the realization by someone that a problem exists for which some corrective action should be taken. This might be the identification of some defect in a current machine design by an engineer or the perception of a new product marketing opportunity by a salesperson. Definition of the problem involves a thorough specification of the item to be designed. This specification includes physical and functional characteristics, cost, quality, and operating performance. Synthesis and analysis are closely related and highly interactive in the design process. A certain component or subsystem of the overall system is conceptualized by the designer, subjected to analysis, improved through this analysis procedure, and redesigned. The process is repeated until the design has been optimized within the constraints imposed on the designer. The components and subsystems are synthesized into the final overall system in a similar interactive manner. Evaluation is concerned with measuring the design against the specifications established in the problem definition phase. This evaluation often requires the fabrication and testing of a prototype model to assess operating performance, quality,reliability, and other criteria. The final phase in the design process is the presentation of the design. This includes documentation of the design by means of drawings, material specifications, assembly lists, and so on. Essentially, the documentation requires that a design database be created. Figure illustrates the basic steps in the design process, indicating its iterative nature.

3. Explain detailly Design review and evaluation:

Checking the accuracy of the design can be accomplished conveniently on the graphics terminal. Semiautomatic dimensioning and tolerancing routines which assign size specifications to surfaces indicated by the user help to reduce the possibility of dimensioning errors. The designer can zoom in on part design details and magnify the image on the graphics screen for close scrutiny. A procedure called layering is often helpful in design review. For example, a good application of layering involves overlaying the geometric image of the final shape of the machined part on top of the image of the rough casting. This ensures that sufficient material is available on the casting to acccomplish the final machined dimensions. This procedure can be performed in stages to check each successive step in the processing of the part. Another related procedure for design review is interference checking. This involves the analysis of an assembled structure in which there is a risk that the components of the assembly may occupy the same space. This risk occurs in the design of large

chemical plants, air-separation cold boxes, and other complicated piping structures. One of the most interesting evaluation features available on some computer aided design systems is kinematics. The available kinematics packages provide the capability to animate the motion of simple designed mechanisms such avisualization of the operation of the mechanism and helps to ensure against interference with other components. Without graphical kinematics on a CAD system, designers must often resort to the use of pin-and-cardboard models to represent the mechanism. commercial software packages are available to perform kinematic analysis. Among these are programs such as ADAMS (Automatic Dynamic Analysis of Mechanical Systems), developed at the University of Michigan. This type of program can be very useful to the designer in constructing the required mechanism to accomplish a specified motion and/or force. Automated drafting

Automated drafting involves the creation of hard-copy engineering drawings directly from the CAD data base. In some early computer-aided design departments, automation of the drafting process represented the principal justification for investing in the CAD system. Indeed, CAD systems can increase productivity in the drafting function by roughly five times over manual drafting. selves especially well to the drafting process. These features include automatic dimensioning, generation of crosshatched areas, scaling of the drawing, and the capability to develop sectional views and enlarged views of particular path details. The ability to rotate the part or to perform other transformations of the image (e.g., oblique, isometric, or perspective views), as illustrated in Figure, can be of significant assistance in drafting. Most CAD systems are capable of generating as many as six views of the part. Engineering drawings can be made to adhere to company drafting standards by programming the standards into the CAD system. Figure shows an engineering drawing with four views displayed. This drawing was produced automatically by a CAD system. Note how much the isometric view promotes a higher level of understanding of the object for the user than the three orthographic views. Parts classification and coding

In addition to the four CAD functions described above, another feature of the CAD data base is that it can be used to develop a parts classification and coding system. Parts classification and coding involves the grouping of similar part designs into classes, and relating the similarities by mean of a coding scheme. Designers can use the classification and coding system to retrieve existing part designs rather than always redesigning new parts.

4. How to create the manufacturing data base

Another important reason for using a CAD system is that it offers the opportunity to develop the data base needed to manufacture the product. In the conventional manufacturing cycle practiced for so many years in industry, engineering drawings were prepared by design draftsmen and then used by manufacturing engineers to develop the process plan (i.e., the "route sheets"). The activities involved in designing the product were separated from the activities associated with process planning. Essentially, a two-step procedure was employed. This was both time consuming and involved duplication of effort by design and manufacturing personnel.

In an integrated CAD/CAM system, a direct link is established between product design and manufacturing: It" is the goal of CAD/CAM not only to automate certain phases of design and certain phases of manufacturing, but also to automate the transition from design to manufacturing. Computer-based systems have been developed which create much of the data and documentation required to plan and manage the manufacturing operations for the product.

The manufacturing data base is an integrated CAD/CAM data base. It includes all the data on the product generated during design (geometry data, bill of materials and parts lists, material specifications, etc.) as well as additional data required for manufacturing much of which is based Oll the product design. Figure 4.lO shows how the CAD/CAM data base is related to design and manufacturing in a typical production-oriented company.

5. Write the steps involved Productivity improvement in design.

Increased productivity translates into a more competitive position for the firm because it will

reduce staff requirements on a given project. This leads to lower costs in addition to improving

response time on projects with tight schedules. Surveying some of the larger CAD/CAM vendors, one

finds that the Productivity improvement ratio for a designer/draftsman is usually given as a range,

typically from a low end of 3: l to a high end in excess of lO: l (often far in excess of that figure).

There are individual cases in which productivity has been increased by a factor of lOO, but it would

be inaccurate to represent that figure as typical. TABLE Potential Benefits That May Result from

implementing CAD as Part of an Integrated CAD/CAM System.

1. Improved engineering productivity 2. Shorter lead times 3. Reduced engineering personnel requirements 4. Customer modifications are easier to make 5. Faster response to requests for quotations 6. Avoidance of subcontracting to meet schedules

7. Minimized transcription errors 8. Improved accuracy of design 9. In analysis, easier recognition of component interactions 10. Provides better functional analysis to reduce prototype testing 11. Assistance in preparation of documentation 12. Designs have more standardization 13. Better designs provided 14. Improved productivity in tool design 15. Better knowledge of costs provided 16. Reduced training time for routine drafting tasks and NC part programming 17. Fewer errors in NC part programming 18. Provides the potential for using more existing parts and tooling 19. Helps ensure designs are appropriate to existing manufacturing techniques 20. Saves materials and machining time by optimization algorithms

Multiple choice questions with answers

1. The Press-Pull tool will ________ the face of a solid model in the direction it faces. A. taper B. extrude C. spiral D. none of the above

Answer: Option B

2. The View toolbar will position the view of the 3-D solid toward the ________.

A. front B. left side C. SE isometric D. all of the above

Answer: Option D

3. The Free Orbit tool is found on the ____ toolbar.

A. rotate B. move C. modify D. 3-D Move

Answer: Option C 4. The MASSPROP shortcut will provide the following information.

A. mass B. volume C. bounding box D. all of the above

Answer: Option D

5. The 3-D commands on the Modeling toolbar include ________.

A. box B. sphere C. extrude D. all of the above

Answer: Option D

6. CAD programs which incorporate parametric modeling utilize a system in which the dimensions

control the ________. A. size and shape of the model features B. perspective of the model C. shading used to render the model D. all of the above

Answer: Option A

7. In order to create one solid model from two or more separate solid shapes the drafter will need to

position them and then ________. A. use Union to join them B. use the Join command C. use the Add Parts tool D. none of the above

Answer: Option A

8. The Conceptual Visual Style tool is located on the ________ toolbar. A. Visual Styles

B. Modify C. 3-D Modeling D. All of the above

Answer: Option A 9. When using SolidWorks, once an entity has been defined, it can only be changed by:

A. deleting it and starting over B. changing the input value C. editing D. using the Cut Extrusion function

10. The _________________ function will create a pocket in a SolidWorks model.

A. Extruded Cut B. Extruded Boss/Base C. Fillet D. Arc

Answers: 1. B 2. D 3. C 4. D 5. D 6. A 7. A 8. A 9. C 10 a Fill in the blanks questions with answers

1. Chain type structure is also known as ---------------- 2. Cluster analysis is used in---------------------- 3. Conveyors are used for transportation of goods along--------------------- 4. CRP takes material requirements from MRP to estimate-------------------- estimate of load 5. Cutter is represented with the following word in APT-------------------- 6. Dead reckoning refers to the _ _ _ _ _ _ _ _ _ _ _ _ _ _ vehicle guidance technology 7. Driverless trains, pallet trucks, unit load carriers are referred to ------------------------ 8. Ease with which the system can be expanded to increase total production quantities is called------------------------------- 9. EIA recommends the spindle speed be programmed in _ _ _ _ _ _ _ _ _ _ _ _ 10. EIA standard feed rate code consists of letter F plus _ _ _ _ _ _ _ _ _ _ digits Answer:

1. poly code 2. PFA 3. Fixed path 4. Overall 5. CUTTER 6. Self-guided 7. AGVS

8. Expansion Flexibility 9. rev/min 10. Five

UNIT-II Two marks of questions with answers

1. What is hidden line removal?

Hidden line removal (HLR) is the method of computing which edges are not hidden by

the faces of parts for a specified view and the display of parts in the projection of a model into

a 2D plane.

2. What is powder shading?

Powder shading is a sketching shading method. In this style, the stumping powder and

paper stumps are used to draw a picture. This can be in color. The stumping powder is smooth

and doesn't have any shiny particles. The poster created with powder shading looks more

beautiful than the original. The paper to be used should have small grains on it so that the

powder remains on the paper.

3. Write down Top-down assembly design.

creation of a component while work in the active part. Hence, the active part will be an

assembly part.

4. Define tolerance stack-up

Tolerance stack-up computations show the collective effect of part tolerance with

tolerances

to obtain total part tolerance, then evaluating that to the existing gap in order to see if the

design will work suitably.

5. Define Interference free matrix.

An interference-free matrix shows interference between two components, when one

component is moved, in a given assembly direction, into an assembled location, with another

component already in an assembled location. Assembly actions that result in interferences are

ferences are


1. Give short notes on surface model?

2. Give an brief account on Hermite Bicubic Surface.

3. Write down the Advantages Surface modelling

Eliminates ambiguity and non-uniqueness present in wireframe models by hiding lines not seen.

Renders the model for better visualization and presentation, objects appear more realistic.

Provides the surface geometry for CNC machining. Provides the geometry needed for mold and die design. Can be used to design and analyze complex free- formed surfaces (ship hulls,

airplane fuselages, car bodies, Surface properties such as roughness, color and reflectivity can be assigned and

demonstrated.

4. What is geometry and topology?

GEOMETRY AND TOPOLOGY

The above figure illustrates the difference between geometry and topology. The

geometry that defines the object is the lengths of lines, areas of surfaces, the angles between

the lines, and the radius and the center of the cylinder and the height. On the other hand,

topology (sometimes called combinatorial structure), is the connectivity and associativity of

the object entities. It has to do with the notion of neighborhood and determines the relational

information between object entities. From a user point of view, geometry is visible and

topology is considered to be non-graphical relational information that is stored in solid model

databases and are not visible to users.

SOLID ENTITIES

There are various basic building blocks, so called, primitives that can be combined in

certain boolean operations to construct complex models. They include

Block Cylinder Cone Sphere Wedge Torus

5. Write short notes on Constructive Solid Geometry (CSG)? This is based on the topological notion that a physical object can be divided into a set

of primitives that can be combined in a certain order following a set of rules (i.e. Boolean

operations) to form the object. The basic elements are block, cylinder, cone, sphere, wedge,

and torus and building operations are Boolean operations. The following bearing support was

constructed with various primitives in a certain sequence by CSG technique.


1. Explain the algebraic geometry of the surface modelling The two fields of algebraic geometry and algorithmic geometry, though closely related, are

traditionally represented by almost disjoint communities. Both fields deal with curves and surfaces but objects are represented in different ways. While algebraic geometry defines objects by the mean of equations, algorithmic geometry use to work with linear models. The current trend is to apply algorithmic geometry algorithms to non linear models such as those found in algebraic geometry. Such algorithms play an important role in many practical fields such as Computer Aided Geometric Design. Their use raises important questions when it comes to developing software featuring such models. First, the manipulation of their representation implies the use of symbolic numeric computations which still represent one major research interest. Second, their visualization and manipulation is not straightforward because of their abstract nature. The first part of this thesis covers the use of algebraic methods in geometric modeling, with an emphasis on topology, intersection and self-intersection for arrangement computation of semi-algebraic sets with either implicit or parametric representation. Special care is given to the genericity of the algorithms which can be specified whatever the context, and then specialized to meet specific representation requirements. The second part of this thesis presents a prototype of an algebraic geometric modeling environment which aim is to provide a generic yet efficient way to model with algebraic geometric objects such as implicit or parametric curves or surfaces, both from a user and developer point of view, by using symbolic numeric computational libraries as a backend for the manipulation of the polynomials defining the geometric objects.

Solid modeling has emerged as a central area of research in such diverse applications as CAD (Computer-Aided Design) and CAM (ComputerAided Manufacturing) in automobile, aeronautic, architecture or movie industries. To specify elaborated shapes, solid modeling mainly has recourse to two families of representations. The first one is a constructive representation called CSG (Constructive Solid Geometry) which consists in assembling elements of simpler geometry such as cubes or spheres by the mean of boolean operations like union, intersection or difference. With this approach, a solid is represented by a tree which leaves are primitive solids and internal nodes are either rigid motions (translation, rotation, scaling) or boolean operations. The second one, called B-Rep (Boundary Representation), describes objects by their boundaries in terms of n-dimensional entities such as vertices (0-dimensional entity), edges (1-dimensional entity), faces (2-dimensional entity), volumes (3-dimensional entity) and so on. The topological model is then a structure gathering these n-dimensional entities together with incidency and adjacency relationships. CSG and B-Rep representations have inherent strength and weaknesses. CSG models are intuitive and offer an easy workflow for design. B-Rep models are more flexible for many operations. As a field, solid modeling spans several disciplines from computer science to mathematics. It is therefore a broad subject that benefits a diversity of viewpoints. In particular it finds its main entities in geometric modeling with curves and surfaces which have brought powerful design possibilities e.g. with freeform surface modeling. Curves and surfaces with algebraic representation feature many advantages which have made of them the representation of choice in CAD. First they provide better accuracy by their exact nature. Second, they yield compact models. Such representations include implicit and parametric ones.

2. Explain the blending function of surface modeling

Smooth curves and surfaces must be generated in many computer graphics applications. Many real-world objects are inherently smooth (fig.1), and much of computer graphics involves modeling the real world. Computer-aided design (CAD), high-quality character fonts, data plots, and artists' sketches all contain smooth curves and surfaces. The path of a camera or object in an animation sequence is almost always smooth; similarly, a path through intensity or color space must often be smooth. The need to represent curves and surfaces arises in two cases: 1. in modeling existing objects (a car, a face, a mountain); 2. in modeling "from scratch" (so-called image synthesis), where no preexisting physical object is being represented. The process of modelling is much easier, if mathematical description of an abject, or at least of part of an object may be applied. In the first case, however, a mathematical description of the object may be unavailable. One way of solution, is to use as a model the coordinates of the infinitely many points of the object, but this is not feasible for a computer with finite storage. More often, the object is merely approximated with pieces (called patches, in the case of surface modelling) of planes, spheres, or other shapes that are easy to describe mathematically, and require that points on the model be close to corresponding points on the object. In the second case, when there is no preexisting object to model, the user creates the object in the modeling process; hence, the object matches its representation exactly, because its only embodiment is the representation. To create the object, the user may sculpt the object interactively, describe it mathematically, or give an approximate description to be "filled in" by some program. In CAD, the computer representation is used later to generate physical realizations of the abstractly designed object.

The general area of surface modeling is quite broad, and only a few most common representations for 3D surfaces are mentioned below: 1. polygon mesh surfaces, 2. parametric surfaces, 3. quadric surfaces, 4. free-form modeling Our goal is to introduce and give an algorithmic description of the process of free-form modelling of surfaces. Nevertheless, to understand all the

concepts needed, we have to introduce polygon mesh surfaces, parametric surfaces, and quadric surfaces. 1.1. Polygon meshes A polygon mesh is a set of connected polygonally bounded planar surfaces. Open boxes, cabinets, and building exteriors can be easily and naturally represented by polygon meshes, as can volumes bounded by planar surfaces. Polygon meshes can be used, although less easily, to represent objects with curved surfaces, as in fig. 2, however, the representation is only approximate. The obvious errors in the representation can be made arbitrarily small by using more and more polygons to create a better piecewise linear approximation, but this increases space requirements and the execution time of algorithms processing the representation. Furthermore, if the image is enlarged, the straight edges again become obvious. The polygon meshes have advantages and disadvantages:

by selecting suitable level of polygon size or representation, the 3D surface may be approximated with a required precision,

if special data structures are employed, the storage of polygon mesh in computer memory may be minimized, but usually there is trade-off between the amount of memory needed and processing time required,

polygon meshes are sensible to many common transformations of 3D objects, like rotation, translation, scaling, perspective transformation, etc., and special reformulation of an algorithm used to maintain the mesh is needed,

enlargement of a picture makes approximation of an object by polygon mesh more inaccurate, and special efforts to fix the presentation are needed, not invariant under basic geometric transforms requires different representations at internal, external, etc. levels There are different ways of presentation polygon meshes in computer memory:

nates, and the vertices are stored in the order in which they would be encountered travelling around the polygon);

indices (or pointers) into the vertex list);

in which each edge occur just once; in turn each edge in the edge list points to the two vertices in the vertex list defining the edge, and also to the one or two polygons to which the edge belongs).

3. Draw and explain surface revolution

Surface of revolution is generated by rotation of a plane curve z = f(x) about an axis Oz called the axis of the surface of revolution. The resulting surface therefore always has azimuthal symmetry. Hence, an explicit equation of a surface of revolution can be presented in the following form: z ¼ f ðrÞ ¼ f ð is the distance a point of the surface from the axis of rotation. Right cylindrical and conical surfaces are examples of surfaces generated by a straight line when the line is coplanar with the axis, as well as hyperboloids of one sheet when the line is skew to the axis. A sphere is a surface of revolution of a circle around an axis which runs through the center of the circle. If the circle is rotated about a coplanar axis, not crossing the circle, then it generates a torus. Meridians are the lines of intersections of a surface of revolution with planes passing through an axis of rotation. All meridians of one surface of revolution are congruent to the rotated curve.Aplane passing through the axis of the surface of revolution is called the meridian plane. It is the plane of symmetry of the surface. Any surface of revolution has the infinite number of planes of symmetry. Parallels are the lines of intersection of the surface with planes orthogonal to an axis of rotation. Meridians and parallels of a

surface of revolution are the lines of principal curvatures. Any normal of surfaces of revolution intersects its axis of rotation.

A surface of revolution having more than one axis of rotation is a sphere or a plane. Tangents to all meridians in the points located on one parallel circle are lines on the tangent conical (or cylindrical) surface of revolution, which is created by the revolution of the tangent about the axis of the rotation. A vertex of the tangent conical surface is located on the axis of revolution. A parallel is called the neck circle, if tangent planes to the surface of revolution in the points on this circle are parallel to the axis of revolution and the tangent cylindrical surface is located inside the surface of revolution. A parallel is called the equator circle, if tangent planes to the surface of revolution in the points on this circle are parallel to the axis of revolution and the tangent cylindrical surface is located outside the surface of revolution. A parallel is called the crater circle, if tangent plane to the surface of revolution in the points on this circle is perpendicular to the axis of revolution and normal to the surface of revolution in the points of this parallel are parallel to the axis of revolution and form the normal cylindrical surface. Umbilical points of a surface of revolution are placed on those latitudes on which a center of curvature of a meridian is located on the axis of rotation. Sphere is umbilical surface. Under Alexis-Claude Clairaut theorem, the product of a radius of a parallel into cosines of an angle of intersection of the geodesic line with the parallel is constant along the geo disincline. A surface of revolution admits bending into another surface of revolution and a net of lines of principal curvatures is remained. Parametrical equations of arbitrary surface of revolution are r ¼ rðr; bÞ ¼ r cos bi þ r sin bj þ f ðrÞk:

4. Explain Bezier curve.

To see why splines are important, lets consider the problem of designing an aircraft wing. Lets assume that the Air Force is designing the latest and greatest jet fighter plane, and the wing is currently being designed according to specifications that include and promote optimal behavior under extreme turbulence due to mach speeds. To even complicate the design further, the wing has to look nice on the rest of the jet so as to promote more military funding and generate recruits into the Air Force. There are many different possible designs for a wing, some that are more optimal than others, and some that are more aesthetically pleasing that others as well. To find a balance between optimizing the air flow around the wing and how the shape looks is quite a task. Assume for a moment that your job as a visualization specialist is to make use of the computer system that utilizes recorded data from an aircraft testing facility.

Their system is able to relate the flow of turbulence around the wing of an aircraft to the shape of the aircrafts wing. You are asked to create a piece of software using their model to allow an efficient way for a designer to specify an optimal and aesthetically pleasing shape for the wing. The relation between shape and turbulence is already completed, so it is your job to give global control to the designer. Mainly, a way of specifying smooth curves on a computer screen is required, and splines

are the natural way of completing the task. In order to effectively represent a smooth curve on a computer screen, we need to somehow approximate it. We come to this realization upon the simple fact that a computer can only draw pixels, which have a predefined width and height.

If you get really close to an LCD screen and observe the tiny squares making up the outline of

at best. Rational Bezier Curves Now that we understand Bezier curves of degree k, we can consider

information than just a point {x, y, z} #3. The problem with just a regular point is that there is no info on how to project it. Homogeneous coordinates exist in order to make the projective transformation easier to work with [5]. The rational form has advantages in that it can represent a wide range of curves, and surfaces (more on surfaces in a little while).

Curves could be in the form of circles, ellipses, parabolas, and hyperbolas; surfaces can be in the form of spheres, ellipsiods, cylinders, cones, paraboloids, hyperboloids, and hyperbolic paraboloids [1]. The only difference in Rational Bezier curves is that the coordinates that specify the curve are in one dimension higher than their nonrational counterpart. For example, if we wish to

for the transition between regular and homogeneous coordinate space. Let h be a map from homogenous coordinate space to regular space, then we define h as h(x, y, x, w)=(x/w, y/w, z/w)

5.Draw and explain CSG OpenMOC uses constructive solid geometry (CSG) to represent complex reactor models in

software. The constructive solid geometry formulation is the method of choice for many advanced modeling software packages, including some Computer-aided Design (CAD) implementations. CSG allows complex spatial models to be built using boolean operations - such as intersections and unions - of simple surfaces and building blocks termed primitives, as illustrated in Figure 1 [Wikipedia]. The constructive solid geometry approach is well suited for reactor models which typically are highly structured and contain repeating patterns. This is the case for commercial PWRs and BWRs whose cores are built out of a rectangular lattice of fuel assemblies, each of which is a rectangular lattice of fuel pins.

There are a number of benefits to using the CSG formulation. First, CSG enables simulation codes to significantly reduce the memory footprint required to model the geometry. For example, rather than representing each fuel pin explicitly in memory, a fuel pin primitive is represented by a single data structure. A second major benefit to the CSG formulation is that it is a general and extensible approach which allows for ray tracing routines to be written in an abstract fashion that is independent of the primitives themselves. The constructive solid geometry formulation in OpenMOC is predicated upon the use of several key objects which allow one to construct a spatial model from simple primitives in a hierarchical fashion. The following sections describe each of these fundamental objects in order of increasing complexity. The reader should note that the CSG formulation in

OpenMOC is presently only capable of describing the 2D -plane, though an extension to 3D would be straightforward.

Section 4.1.1 develops the formulation for surfaces which are used to divide space into separate unique halfspaces. Section 4.1.2 describes universes which represent the entirety of 2D (or

ure of cells. Section 4.1.3 describes cells which contain one or more surfaces that bound a subset of space filled by either a material or a universe. Section 4.1.4 describes lattices which are used to create a bounded union of universes through a series of coordinate transformations. A typical hierarchy for the way in which surfaces, universes, cells and lattices are constructed to represent a reactor model in OpenMOC

.

Multiple choice questions with answers 1. When using SolidWorks, once an entity has been defined, it can only be changed by: a. deleting it and starting over b. changing the input value c. editing d. using the Cut Extrusion function 2. The _________________ function will create a pocket in a SolidWorks model. a. Extruded Cut b. Extruded Boss/Base c. Fillet d. Feature Manager 3. Solid models can be modified by: a. adding volume using Boss Extrusion b. removing volume using Extrusion Cut c. adding a fillet to a feature d. all of these are correct 4. In SolidWorks, material is assigned to a solid in the: a. Feature Manager b. Sketch mode c. Solid Creation mode d. none of these are correct 5. All of the following are processes (as opposed to input or output) in a manufacturing business a. Material b. Planning c. Documenting d. Designing 6. All of the following operations can make use of the CAD database a. Designing b. Marketing c. Producing d. None of the above 7. All of the following are part of the refinement process a. Modeling b. Design analysis c. Problem identification d. Design visualization

8. Which type of model is likely to be created with a rapid prototyping system? a. Mathematical model b. Wireframe model c. Surface model d. Scale model 9. Which of the following is considered a type of mechanism analysis? a. Functional analysis b. Kinematic analysis c. Finite Element analysis d. Human Factors analysis

10. Which of the following would be used to help determine the spacing between earpiece and mouthpiece on a phone? a. Dynamic analysis b. Kinematic analysis c. Finite Element analysis d. Human Factors analysis

Answers:

1. C 2.a 3.b 4.a 5.a 6.d 7.c 8.d 9.b 10.d Fill in the blanks questions with answers

1. Ability to change product composition while maintaining the same total production quantity is called --------------------------------------:-> 2. Ability to economically produce parts in high and low quantities is called--------------------------------------------- :-> 3. Acceptance sampling is most frequently used in--------------------------------- :-> 4. Acceptance sampling is not followed in------------------------------------ :-> 5. Agile manufacturing is implemented at the-------------------------------- :-> 6. Among the following which one is based on route sheet? ------------------------------------:-> 7. An alternative form of loop layout is _ _ _ _ _ _ _ _ _ _ _ _ layout :-> 8. Another form of Lean manufacturing is------------------------------------------- :-> 9. APT is a _ _ _ _ _ _ _ _ _ _ _ language for CNC machines :->

10. Automated guided vehicles are frequently used in----------------------------- :-> Answers 1. Product Mix Flexibility 2. Volume Flexibility 3. Mass production 4. Japanese industries 5. Enterprise level 6. PFA 7. Rectangular 8.Agile manufacturing 9. Higher level language 10. Mass production

UNIT-III Two marks of questions with answers

1. Define NC system? NC is defined as a form of programmable automation in which the process iscontrolled

by alphanumeric data. 2. What is MCU?

MCU is a hardware system which reads, interprets and translates the programof instructions into mechanical action of machine tool.

3. Define CNC? CNC is defined as a NC system that utilizes a dedicated, stored computer program to

perform some or the entire basic NC functions. 4. Write any four application of NC system?

Application are in aero equipment; printed circuit boards; coil winding; automobile parts; and blue print of complex shapes.

5. Define DNC? Direct numerical control system is defined as a manufacturing system in which a

number of machine tools are controlled by a computer through direct connection and in real time.


1. Write short notes on NC procedure To utilize numerical control in manufacturing, the following steps must be

accomplished. Process Planning. The engineering drawing of the workpart must be interpreted in terms of the manufacturing processes to be used. this step is referred to as process planning and it is concerned with the preparation of a route sheet. The route sheet is a listing of the sequence of operations which must be performed on the workpart. It is called a route sheet because it also lists the machines through which the part must be routed in order to accomplish the sequence of operations. We assume that some of the operations will be performed on one or more NC machines.

Part programming. A part programmer plans the process for the portions of the job to be accomplished by NC. Part programmers are knowledgeable about the machining process and they have been trained to program for numerical control. They are responsible for planning the sequence of machining steps to be performed by NC and to document these in a special format. There are two ways to program for NC.


In manual programming, the machining instructions are prepared on a form called a

part program manuscript. The manuscript is a listing of the relative cutter/work piece positions which must be followed to machine the part. In computer-assisted part programming, much of the tedious computational work required in manual part programming is transferred to the computer. This is especially appropriate for complex work piece geometries and jobs with many machining steps. Use of the computer in these situations results in significant savings in part programming time.

2. Answer in brief about Fixed zero and floating zero:

The programmer must determine the position of the tool relative to the origin (zero point) of the coordinate system. NC machines have either of two methods for specifying the zero point. The first possibility is for the machine to have a fixed zero. In this case, the origin is always located at the same position on the machine. Usually, that position is the southwest comer (lower left-hand comer)of the table and all tool locations will be defined by positive x and y coordinates.

The second and more common feature on modern NC machines allows the machine operator to set the zero point at any position on the machine table. This feature is called floating zero. The part programmer is the one who decides where the zero point should be located. The decision is based on part programming convenience. For example, the work part may be symmetrical and the zero point should be established at the center of symmetry. Absolute versus incremental positioning

3. Give an brief notes on Straight-cut NC

Straight-cut control systems are capable of moving the cutting tool parallel to one of the major axes at a controlled rate suitable for machining. It is therefore appropriate for performing

milling operations to fabricate workpieces of rectangular configurations. With this type of NC system it is not possible to combine movements in more than a Single axis direction. Therefore, angular cuts on the workpiece would not be possible. An example of a straight-cut operation is shown in Figure

4. Write down the application of Numerical control systems.

Numerical control systems are widely used in industry today, especially in the metalworking industry. By far the most common application of NC is for metal cutting machine tools. Within this category, numerically controlled equipment has been built to perform virtually the entire range of material removal processes, including: Milling, Drilling and related processes Boring, Turning, Grinding, Sawing

Within the machining category, NC machine tools are appropriate for certain jobs and inappropriate for others. Following are the general characteristics of production jobs in metal machining for which numerical control would be most appropriate:

Parts are processed frequently and in small lot sizes.

The part geometry is complex.

Many operations must be performed on the part in its processing.

Much metal needs to be removed.

Engineering design changes are likely.

Close tolerances must be held on the workpart.

It is an expensive part where mistakes in processing would be costly.

The parts require lOO% inspection

5. Write a short notes on Contouring motions.

Contouring commands are somewhat more complicated because the tool's position must be continuously controlled throughout the move. To accomplish this control, the tool is directed along two intersecting surfaces as shown in Figure 8.lO. These surfaces have very specific names in APT:

l. Drive surface. This is the surface (it is pictured as a plane in Figure 8.lO) that guides the side of the cutter.

Part surface. This is the surface (again shown as a plane in the figure) on which the bottom of the cutter rides. The reader should note that the "part surface" mayor may not be an actual surface of the workpart. The part programmer must define this plus the drive surface for the purpose of maintaining continuous path control of the tool.

There is one additional surface that must be defined for APT contouring motions:

Three surfaces in APT contouring motions which guide the cutting tool. Five marks of questions with answers

1. What are the steps involved in NC procedure. NC procedure


l. Process Planning. The engineering drawing of the work part must be interpreted in terms

of the manufacturing processes to be used. this step is referred to as process planning and it is

concerned with the preparation of a route sheet. The route sheet is a listing of the sequence of

operations which must be performed on the workpart. It is called a route sheet because it also lists the

machines through which the part must be routed in order to accomplish the sequence of operations.

We assume that some of the operations will be performed on one or more NC machines.

2. Part programming. A part programmer plans the process for the portions of the job to be






Computer-assisted part programming


program manuscript. The manuscript is a listing of the relative cutter/work piece positions which must

be followed to machine the part. In computer-assisted part programming, much of the tedious


especially appropriate for complex work piece geometries and jobs with many machining steps. Use

of the computer in these situations results in significant savings in part programming time.

Tape preparation

manual part programming, the punched tape is prepared directly from the part program manuscript on

a typewriter like device equipped with tape punching capability. In computer-assisted part

programming, the computer interprets the list of part programming instructions, performs the

necessary calculations to convert this into a detailed set of machine tool motion commands, and then

controls a tape punch device to prepare the tape for the specific NC machine.

Tape verification. After the punched tape has been prepared, a method isusually provided for

checking the accuracy of the tape. Some times the tape is checked by running it through a computer

program which plots the various tool movements (or table movements) on paper. In this way, major

errors in the tape can be discovered. The "acid test" of the tape involves trying it out on the machine

tool to make the part. A foam or plastic material is sometimes used for this tryout. Programming errors

are not uncommon, and it may require about three attempts before the tape is correct and ready to use.

Production. The final step in the NC procedure to use the NC tape in production. This involves

ordering the raw workparts specifying and preparing the tooling and any special fixturing that may be

required, and setting up The NC machine tool for the job. The machine tool operator's function during

production is to load the raw workpart in the machine and establish the starting position of the cutting

tool relative to the workpiece. The NC system then takes over and machines the part according to the

instructions on tape. When the part is completed, the operator removes it from the machine and loads

the next part.

2.With neat diagram draw and explain

NC COORDINATE SYSTEMS






The second and more common feature on modern NC machines allows the machine operator

to set the zero point at any position on the machine table. This feature is called floating zero. The part

programmer is the one who decides where the zero point should be located. The decision is based on

part programming convenience. For example, the work part may be symmetrical and the zero point

should be established at the center of symmetry.











3. What are the various types of motion control system In order to accomplish the machining process, the cutting tool and workpiece must be moved

relative to each other. In NC, there are three basic types of motion control systems: -

l. Point-to-point

4. Straight cut

5. Contouring

Point-to-point NC Point-to-point (PTP) is also sometimes called a positioning system. In PTP, the objective of

the machine tool control system is to move the cutting tool to a predefined location. The speed or path

by which this movement is accomplished is not import in point-to-point NC. Once the tool reaches the

desired location, the machining operation is performed at that position.

NC drill presses are a good example of PTP systems. The spindle must first be positioned at a

particular location on the work piece. This is done under PTP control. Then the drilling of the hole is

performed at the location, and so forth. Since no cutting is performed between holes, there is no need

for controlling the relative motion of the tool and work piece between hole locations. Figure illustrates

the point-to-point type of control.

Positioning systems are the simplest machine tool control systems and are therefore the least

expensive of the three types. However, for certain processes, such as drilling operations and spot

welding, PIP is perfectly suited to the task and any higher level of control would be unnecessary.

Straight-cut NC Straight-cut control systems are capable of moving the cutting tool parallel to one of the major axes at

a controlled rate suitable for machining. It is therefore appropriate for performing milling operations

to fabricate workpieces of rectangular configurations. With this type of NC system it is not possible to

combine movements in more than a Single axis direction. Therefore, angular cuts on the workpiece

would not be possible. An example of a straight-cut operation is shown in Figure

Straight-cut system

Contouring NC Contouring is the most complex, the most flexible, and the most expensive type of machine

tool control. It is capable of performing both PTP and straight-cut operations. In addition, the

distinguishing feature of contouring NC systems is their capacity for simultaneous control of more

than one axis movement of the machine tool. The path of the cutter is continuously controlled to

generate the desired geometry of the workpiece. For this reason, contouring systems are also called

continuous-path NC systems.

Straight or plane surfaces at any orientation, circular paths, conical shapes, or most any other mathematically definable form are possible under contouring control. Figure illustrates the versatility of continuous path NC.

4. Write down the application of the numerical control APPLICATIONS OF NUMERICAL CONTROL

Numerical control systems are widely used in industry today, especially in the metalworking

industry. By far the most common application of NC is for metal cutting machine tools. Within this

category, numerically controlled equipment has been built to perform virtually the entire range of

material removal processes, including:

Milling, Drilling and related processes Boring, Turning, Grinding, Sawing Within the machining category, NC machine tools are appropriate for certain jobs and

inappropriate for others. Following are the general characteristics of production jobs in metal

machining for which numerical control would be most appropriate:

Parts are processed frequently and in small lot sizes.

The part geometry is complex.

Many operations must be performed on the part in its processing.

Much metal needs to be removed.

Engineering design changes are likely.

Close tolerances must be held on the workpart.

It is an expensive part where mistakes in processing would be costly.

The parts require lOO% inspection

It has been estimated that most manufactured parts are produced in lot sizes of 5O or fewer. Small-lot

and batch production jobs represent the ideal situations for the application of NC. This is made

possible by the capability to program the NC machine and to save that program for subsequent use in

future orders. If the NC programs are long and complicated (complex part geometry, many operations,

much metal removed), this makes NC all the more appropriate when compared to manual methods of

production. If engineering design changes or shifts in the production schedule are likely, the use of

tape control provides the flexibility needed to adapt to these changes. Finally, if quality and inspection

are important issues (close tolerances, high part cost, lOO% inspection required), NC would be most

suitable, owing to its high accuracy and repeatability.

In order to justify that a job be processed by numerical control methods, it is not necessary that

the job possess every one of these attributes. However, the more of these characteristics that are

present, the more likely it is that the part is a good candidate for NC.

In addition to metal machining, numerical control has been applied to a variety of other operations.

The following, although not a complete list, will give the reader an idea of the wide range of potential

applications of NC Press working machine tools Welding machines Inspection machines Automatic

drafting Assembly machines

Tube bending Flame cutting Plasma arc cutting

Laser beam processes Automated knitting machines Cloth cutting

Automatic riveting Wire-wrap machines

Advantages of NC Following are the advantages of numerical control when it is utilized in the type of

production jobs described.

l. Reduced nonproductive time. Numerical control has little or no effect on the basic metal,

cutting (or other manufacturing) process. However; NC can increase the proportion of time the

machine is engaged in the actual process. It accomplishes this by means of fewer setups, less time in

setting up, reduced work piece handling time, automatic tool changes on some machines, and so on.

In a University of Michigan survey reported by Smith and Evans, a comparison was made

between the machining cycle times for conventional machine tools versus the cycle times for NC

machines. NC cycle times, as a percentage of their conventional counterparts, ranged from 35% for

five-axis machining centers to 65% for presswork punching. The advantage for numerical control

tends to increase with the more complex processes.

Reduced fixturing. NC requires fixtures which are simpler and less costly to fabricate because the

positioning is done by the NC tape rather than the jig or fixture

Reduced manufacturing lead time. Because jobs can be set up more quickly with NC and fewer setups

are generally required with NC, the lead time to deliver a job to the customer is reduced.

Greater manufacturing flexibility. With numerical control it is less difficult to adapt to engineering

design changes alterations of the production schedule, changeovers in jobs for rush orders, and so on.

Improved quality control. NC is ideal for complicated workparts where the chances of human mistakes

are high. Numerical control produces parts with greater accuracy, reduced scrap, and lower inspection

requirements. Reduced inventory. Owing to fewer setups and shorter lead times with numerical control,

the amount of inventory carried by the company is reduced.

Reduced floor space requirements. Since one NC machining center can often accomplish the

production of several conventional machines, the amount of floor space required in an NC shop is

usually less than in a conventional shop.

Disadvantages of NC Along with the advantages of NC, there are several features about NC which must be

considered disadvantages:

Higher investment cost. Numerical control machine tools represent a more sophisticated

and complex technology. This technology costs more to buy than its non-NC counterpart. The higher

cost requires manufacturing managements to use these machines more aggressively than ordinary

equipment.

High machine utilization is essential on order to get reasonable returns on investment. Machine shops

must operate their NC machines two or three sifts per day to achieve this high machine utilization.

Higher maintenance cost. Because NC is a more complex technology and because NC machines are

used harder, the maintenance problem becomes more acute. Although the reliability of NC systems

has been improved over the years, maintenance costs for NC machines will generally be higher than

for conventional machine tools.

Finding and/or training NC personnel. Certain aspects of numerical control shop operations

require a higher skill level than conventional operations. Part programmers and NC maintenance

personnel are two skill areas where available personnel are in short supply. The problems of finding,

hiring, and training these people must be considered a disadvantage to the NC shop

5.Explain detailly about NC part programming methods

Following is a list of the different types of words in the formation of a block. Not very NC

machine uses all the words. Also, the manner in which the words are expressed will differ between

machines. By convention, the words in a block are given in the following order:

SEQUENCE NUMBER (n-words): This is used to identify the block. PREPARATORY WORD (g-words): This word is used to prepare the controller for

instructions that are to follow. For example, the word gO2 is used to prepare the C controller unit for

circular interpolation along an arc in the clockwise direction. The preparatory word l& needed S9 that

the controller can correctly interpret the data that follow it in the block.

COORDINATES (x-, y-, and z-words): These give the coordinate positions of the tool. In a

two-axis system, only two of the words would be used. In a four- or five- axis machine, additional a-

words and V or b-words would specify the angular positions.

Although different NC systems use different formats for expressing a coordinate, we will adopt the

convention of expressing it in the familiar decimal form: For example, x + 7.235 ory-O.5ao. Some

formats do not use the decimal point in writing the coordinate. The + sign to define a positive

coordinate location is optional. The negative sign is, of FEED RATE (f-word): This specifies the feed

in a machining operation. Units are inches per minute (ipm) by convention.

CUTTING SPEED (s-word): This specifies the cutting speed of the process, the rate at which the

spindle rotates.

TOOL SELECTION (t-word): This word would be needed only for machines with a tool turret or

automatic tool changer. The t-word specifies which tool is to be used in the operation. For example,

tO5 might be the designation of a l/2-in. drill bit in turret position 5 on an NC turret drill.

MSCELLANEOUS FUNCTION (m-word): The m-word is used to specify certain miscellaneous or auxiliary functions which may be available on the machine tool.


1) Arrange the below operations in operator controlled machine tool in correct order. (A) Operator (B) Process planing (C) Machine tool (D) Component drawing (E) Completed component

a. (A) (D) (B) (C) (E) b. (D) (B) (C) (A) (E) c. (B) (D) (C) (A) (E) d. (D) (B) (A) (C) (E) ANSWER: Option d. (D) (B) (A) (C) (E)

2) The device, fed to the control unit of NC machine tool which sends the position command signals to sideway transmission elements of the machine, is called as

a. controller b. tape c. feedback unit d. none of the above

3) In NC (Numerical Control) machine tool, the position feedback package is connected between

a. control unit and programmer b. programmer and machine tool c. control unit and machine tool d. programmer and process planning

4) Which of the following options is correct for the control unit and panel of NC (Numerical Control) and CNC (Computer Numerical Control) machine tools?

a. The control unit of NC machine tool works in ON-line mode and the control unit of CNC machine tool works in batch processing mode b. The control unit of NC machine tool works in batch processing mode and the control unit of CNC

machine tool works in ON-line mode c. The control units of both NC and CNC machines work in ON-line mode d. The control units of both NC and CNC machines work in batch processing mode

5) In CNC machine tool, the part program entered into the computer memory

a. can be used only once b. can be used again and again c. can be used again but it has to be modified every time d. cannot say

6) Which of the following statements are correct for CNC machine tool? 1. CNC control unit does not allow compensation for any changes in the dimensions of cutting tool 2. CNC machine tool are suitable for long run applications 3. It is possible to obtain information on machine utilization which is useful to management in CNC machine tool 4. CNC machine tool has greater flexibility 5. CNC machine can diagnose program and can detect the machine defects even before the part is produced

a. (1), (2) and (3) b. (2), (4) and (5) c. (3), (4) and (5) d. (2), (3), (4) and (5)

7) Several machine tools can be controlled by a central computer in

a. NC (Numerical Control) machine tool b. CNC (Computer Numerical Control) machine tool c. DNC (Direct Numerical Control) machine tool d. CCNC (Central-Computer Numerical Control) machine tool

8) Part-programming mistakes can be avoided in

a. NC (Numerical Control) machine tool b. CNC (Computer Numerical Control) machine tool c. Both a. and b. d. None of the above

9) The machine tool, in which calculation and setting of the operating conditions like depth of cut, feed, speed are done during the machining by the control system itself, is called

a. Computer Numerical Control System b. Direct Numerical Control System c. Machining Centre System d. Adaptive Control System

10) Which machine tool reduces the number of set-ups in machining operation, time spent in

setting machine tools and transportation between sections of machines?

a. Computer Numerical Control machine tool b. Direct Numerical Control machine tool c. Adaptive Control Systems d. Machining centre

Answers: 1.d 2.b 3.c 4.b 5.b 6.c 7.c 8.b 9.d 10.d

Fill in the blanks questions with answers 1. Hierarchical structure is known as-------------------------- 2. In _ _ _ _ _ _ _ _ _ _ _ _ _ _ type code, interpretation of symbol does not depend on value of preceding :-> 3. In an APT program which is the last statement _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 4. In CIM the computer is used for------------------------------ 5. In Contouring motion statement the tool always moves along _ _ _ _ _ _ _ _ _ _ _ _ _ _ 6. In FMS, the tools are identified by means of -------------------------------- 7. In G42 G01 X 100 Y40 D05, D05 indicates ----------------------------------: 8. In Kanban, there will be------------------------------------- 9. In OPITZ code 4th digit refers to--------------------------------- 10. In OPITZ code form code is an example of ---------------------------------------

Answers: 1. Mono code 2. Chain type code symbol 3. FINI 4. Controlling throughout enterprise. 5. Drive Surface 6. Bar code 7. Cutter radius 8. Minimum inventory 9. Plain surfaces Mixed Code

UNIT-IV Two marks of questions with answers

1. What are the activities of CAM?

A CAM activity includes process planning, NC part programming, production scheduling, and

computer production monitoring and computer process control.

2. In what way CIM differs from CAD/CAM?

A CIM includes all of the engineering function

business functions that are related to manufacturing.

3. What is group technology?

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

together to get the advantages of similarities in both design and manufacturing attributes.

4. What is meant by part family?

Part family is a collection of parts which are similar either because ofgeometric shape or

because of similar steps that are required in their manufacture.

5. What is meant by PFA method? Production flow analysis is a method for identifying part families and associated machine groupings that uses the information contained on production route sheets rather than on part drawings.

Three marks of questions with answers 1. Give an brief account on part family:

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 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 workpiece 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, long manufacturing lead times, and high cost. Figure shows a production shop of supposedly equivalent capacity, but with the machines arranged into cells. Each cell is organized to specialize in the manufacture of a particular part family.

2. Describe Automated process planning

Because of the problems encountered with manual process planning, attempts have been made in recent years to capture the logic, judgment, and experience required for this important function and incorporate them into computer programs. Based on the characteristics of a given part, the program automatically generates the manufacturing operation sequence. A computer-aided process planning (CAPP) system offers the potential for reducing the routine clerical work of manufacturing engineers. At the same time, it provides the opportunity to generate production routings which are rational, consistent, and perhaps even optimal. Two alternative approaches to computer-aided process planning have been developed. These are:

Retrieval-type CAPP systems (also called variant systems)

Generative CAPP systems

3. What are theBENEFITS OF CAPP ?

Whether it is a retrieval system or a generative system, computer-aided process planning offers a number of potential advantages over manually oriented process planning.

Process rationalization. Computer-automated preparation of operation routings is more likely to be consistent, logical, and optimal than its manual counterpart. The process plans will be consistent because the same computer software is being used by all planners. The process plans tend to be more logical and optimal because the company has presumably incorporated the experience and judgment of its best manufacturing people into the process planning computer software.

Increased productivity of process planners. With computer-aided process planning, there is reduced clerical effort, fewer errors are made, and the planners have immediate access to the process planning data base. These benefits translate into higher productivity of the process planners. One system was reported to increase productivity by 6OO% in the process planning function .

Reduced turnaround time. Working with the CAPP system, the process planner is able to prepare a route sheet for a new part in less time compared to manual preparation. "Ibis leads to an overall reduction in manufacturing lead time.

Improved legibility. The computer-prepared document is neater and easier to read than manually written route sheets. CAPP systems employ standard text, which facilitates interpretation of the process plan in the factory.

Incorporation of other application programs. The process planning system can be designed to operate in conjunction with other software packages to automate many of the time-consuming manufacturing support functions.

4. Write a short notes onAggregate planning: It is a high-level corporate planning activity. The aggregate production plan indicates

production output levels for the major product lines of the company. The aggregate plan must be coordinated with the plans of the sales & marketing departments. Because the aggregate production plan includes products that are currently in production, it must also consider the present & future inventory levels of those products & their component parts. Because new products currently being developed will also be included in the aggregate plan, the marketing plans & promotions for current products & new products must be reconciled against the total capacity resources available to the company.

The production quantities of the major product lines listed in the aggregate plan must be converted into a very specific schedule of individual products, known as the master production schedule (MPS). It is a list of products to be manufactured, when they should be completed & delivered, & it what quantities. A hypothetical MPS for a narrow product set is presented in the table, showing how it is derived from the corresponding aggregate plan in the 2nd table. The master schedule must be based on an accurate estimate of demand & a realistic assessment of the c

5. How MRP Works The MRP processor operates on data contained in the MPS, the BOM file, and the

inventory record file. The master schedule specifies the period-by period list of final products required. The BOM define what material and components are needed for each Product and inventory record files gives the current and future inventory status of each product, component, and material. The MRP processor computers how many of each component and raw material are needed each period levels in the product structure.

Several complicating factors must be considered during the MRP computations. First the quantities of component and subassemblies listed in the solution of Example 25.1 do not account for any of those items that may already be stocked in inventory or are expected to be received as future order. Accordingly, the computed quantities must be adjusted for any inventories on hand or on order, a procedure called netting. For each time bucket, net requirements = gross requirements less on hand inventories and less quantities on order.

Second, quantities of common use items must be combined during parts explosion to

determine the total quantities required for each component and raw material in the schedule. Common use items are raw materials and components that are used on more than one product. MRP collects these common use items from different products to achieve economics in ordering the raw materials and producing the components.


1. Give an detail account on Group technology layout.

The set of similar components can be called as a part family. Since all family members require

similar processes, a machine cell can be built to manufacture the family. This makes

production planning and control much easier because only similar components are considered

for each cell. Such a cell-oriented layout is called a group-technology layout or cellular

layout.

Advantages are gained in group-technology layout

Reduced workpiece handling

Lower setup times.

Less in-process 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.

The three methods for grouping parts into families are:

1.Visual inspection method.

2.Production flow analysis (PFA).

3.Parts classification and coding system.

Visual inspection method:

It is the least sophisticated and least expensive method. It involves the classification of parts

into families by looking at either the physical parts or photographs and arranging them into similar

groupings.

This method is generally considered to be the least accurate of the three.

Production flow analysis (PFA):

The second method, production flow analysis, was developed by J. L.

Burbidge. PFA is a method of identifying part families and associated machine tool groupings by

analyzing the route sheets for parts produced in a given shop. It groups together the parts that have

similar operation sequences and machine routings.

The disadvantage of PFA is that it accepts the validity of existing route sheets, with no

consideration given to whether these process plans are logical or consistent. The production flow

analysis approach does not seem to be used much at all in the United States.

Parts 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 a code number. This classification and coding may be carried out on the entire list of active

parts of the firm, or a sampling process may be used to establish the part families.

Many parts classification and coding systems have been developed throughout the world, and

there are several commercially available packages being sold to industrial concerns.

2. Explain the MICLASS System?







Standardization of engineering drawings Retrieval of drawings 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 from l2 to 3O digits. The first l2 digits are a universal

code that can be applied to any part. Up to l8 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


The CODE system

The CODE system is a parts classification and coding system developed and marketed by

Manufacturing Data Systems, Inc. (MDSI), of Aim 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.

The CODE number has eight digits. For each digit there are l6 possible values (zero through

9 and A through F) which are used to describe the part's 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 the first digit, but

these remaining digits form a chain-type structure. Hence the CODE system possesses a hybrid

structure.

3. Explain various types of planning function? Process planning is concerned with determining the sequence of individual

manufacturing operations needed to produce a given part or product. The resulting operation

sequence is documented on a form typically referred to as a route sheet. The route sheet is a

listing of the production operations and associated machine tools for a work part or assembly.

Traditional process planning

There are variations in the level of detail found in route sheets among different companies

and industries. In the one extreme, process planning is accomplished by releasing the part print to the

steps describing each operation and identifying each work center. In any case, it is traditionally the

task of the manufacturing engineers or industrial engineers in an organization to write these process

plans for new part designs to be produced by the shop. The process planning procedure is very much

dependent on the experience and judgment of the planner. It is the manufacturing engineer's

responsibility to determine an optimal routing for each new part design. However, individual

engineers each have their own opinions about what constitutes the best routing. Accordingly, there are

differences among the operation sequences developed by various planners. We can illustrate rather

dramatically these differences by means of an example.

In one case cited, a total of 42 different routings were developed for various sizes of a

relatively simple part called an "expander sleeve." There were a total of 64 different sizes and styles,

each with its own part number. The 42 routings included 2O different machine tools in the shop.

The reason for this absence of process standardization was that many different individuals

had worked on the parts: 8 or 9 manufacturing engineers, 2 planners, and 25 NC part programmers.

Upon analysis, it was determined that only two different routings through four machines were needed

to process the 64 part numbers. It is clear that there are potentially great differences in the perceptions

among process planners as to what constitutes the "optimal" method of production.

In addition to this problem of variability among planners, there are often difficulties in the

conventional process planning procedure. New machine tools in the factory render old routings less

than optimal. Machine breakdowns force shop personnel to use temporary routings, and these become

the documented routings even after the machine is repaired. For these reasons and others, a significant

proportion of the total number of process plans used in manufacturing are not optimal.

Automated process planning Because of the problems encountered with manual process planning, attempts have been

made in recent years to capture the logic, judgment, and experience required for this important

function and incorporate them into computer programs. Based on the characteristics of a given part,

the program automatically generates the manufacturing operation sequence. A computer-aided process

planning (CAPP) system offers the potential for reducing the routine clerical work of manufacturing

engineers. At the same time, it provides the opportunity to generate production routings which are

rational, consistent, and perhaps even optimal. Two alternative approaches to computer-aided process

planning have been developed. These are:

l. Retrieval-type CAPP systems (also called variant systems) 2. Generative CAPP systems

4. Draw and explain Retrieval type CAPP system and Generative CAPP system? RETRIEVAL - TYPE PROCESS PLANNING SYSTEMS

Retrieval-type CAPP systems use parts classification and coding and group technology as a

foundation. In this approach, the parts produced in the plant aregrouped into part families,

distinguished according to their manufacturing characteristics. For each part family, a standard

process plan is established. The standard process plan is stored in computer files and then retrieved for

new workparts which belong to that family. Some form of parts classification and coding system is

required to organize the computer files and to permit efficient retrieval of the appropriate process plan

for a new workpart. For some new parts, editing of the existing process plan may be required. This is

done when the manufacturing requirements of the new part are slightly different from the standard.

The machine routing may be the same for the new part, but the specific operations required at each

machine may be different. The complete process plan must document the operations as well as the

sequence of machines through which the part must be routed. Because of the alterations that are made

in the retrieved process plan, these CAPP systems are sometimes also called by the name' 'variant

system."

Figure will help to explain the procedure used in a retrieval process planning system. The

user would initiate the procedure by entering the part code number at a computer terminal. The CAPP

program then searches the part family matrix file to determine if a match exists. If the file contains an

identical code number, the standard machine routing and operation sequence are retrieved from the

respective computer files for display to the user. The standard process plan is examined by the user to

permit any necessary editing of the plan to make it compatible with the new part design. After editing,

the process plan formatter prepares the paper document in the proper form.

If an exact match cannot be found between the code numbers in the computer file and the

code number for the new part, the user may search the machine routing file and the operation

sequence file for similar parts that could be used to develop the plan for the new part. Once the

process plan for a new part code number has been entered, it becomes the standard process for future

parts of the same classification.

GENERATIVE PROCESS PLANNING SYSTEMS

Information flow in a retrieval-type computer-aided process planningsystem.

Generative process planning involves the use of the computer to create an individual process

plan from scratch, automatically and without human assistance. The computer would employ a set of

algorithms to progress through the various technical and logical decisions toward a final plan for

manufacturing. Inputs to the ~ tern would include a comprehensive description of the work part. This

may involve the use of some form of part code number to summarize the work part data, but does not

involve the retrieval of existing standard plans. Instead, the general CAPP system synthesizes the

design of the optimum process sequence, based an analysis of part geometry, material, and other

factors which would influence manufacturing decisions.

In the ideal generative process planning package, any part design could presented to the

system for creation of the optimal plan. In practice, cu generative- type systems are far from universal

in their applicability. They after fall short of a truly generative capability, and they are developed for a

some limited range of manufacturing processes.

5. Explain machinability data system?

A machinability data base system, which forms a part of the common manufacturing data base and is

also capable of adapting and optimizing the machining data, is an important component of automated

manufacturing systems. A generative type machinability data base system is proposed for automating

the adaptation and optimization of the machining data. A typical machining problem is formulated and

analyzed to illustrate the proposed adaptive optimization methodology.

Aggregate planning: It is a high-level corporate planning activity. The aggregate production

plan indicates production output levels for the major product lines of the company. The aggregate plan

must be coordinated with the plans of the sales & marketing departments. Because the aggregate

production plan includes products that are currently in production, it must also consider the present &

future inventory levels of those products & their component parts. Because new products currently

being developed will also be included in the aggregate plan, the marketing plans & promotions for

current products & new products must be reconciled against the total capacity resources available to

the company.

The production quantities of the major product lines listed in the aggregate plan must be

converted into a very specific schedule of individual products, known as the master production

schedule (MPS). It is a list of products to be manufactured, when they should be completed &

delivered, & it what quantities. A hypothetical MPS for a narrow product set is presented in the table,

showing how it is derived from the corresponding aggregate plan in the 2nd table. The master

production capacity.

Master Production Schedule

Products included in the MPS divide into 3 categories: (1) firm customer orders, (2) forecasted

demand, & (3) spare parts. Proportions in each category vary for different companies, & in some cases

one or more categories are omitted. Companies producing assembled products will generally have to

handle all three types. In the case of customer orders for specific products, the company is usually

obligated to deliver the item by a particular date that has been promised by the sales department. In

the second category, production output quantities are based on statistical forecasting techniques

applied to previous demand patterns, estimates by the sales staff, & other sources. For many

companies forecasted demand constitutes the largest portion of the master schedule. The third

category consists of repair parts that e

sent directly to the customer. Some companies exclude this third category from the master schedule

since it does not represent end products.

The MPS is generally considered to be a medium-range plan since it must take into account the

lead times to order raw materials & components, produce parts in the factory, & then assemble the end

products. Depending on the product, the lead times can range from several weeks to many months; in

some cases, more than a year. The MPS is usually considered to be fixed in the near term. This means

that changes are not allowed within about a six week horizon because of the difficulty in adjusting

production schedules within such a short period. However, schedule adjustments are allowed beyond

six weeks to cope with changing demand patterns or the introduction of new products. Accordingly,

we should note that the aggregate production plan is not the only input to the master schedule. Other

inputs that may cause the master schedule to depart from the aggregate plan include new customer

orders & changes in sales forecast over the near term.


1.Process of operations with little or no human labour, using specialized equipment a) Interfacing b) Automation c) Autonomation d) Processing 2. Mass Production produces the Quantity a) Minimum b) Less than 100

c) More than 10000 d) As per order 3. The main goal of the lean production is a) More Resources b) More Customer Satisfaction c) More Inventory d) More workers 4. Benefit of CAPP a.Minimum error b. Cost Reduction c. Time Reduction d. All 5.MRP leads a. Planning b. Scheduling c. Planning and scheduling d. None 6If a part is large & heavy _______ layout is suitable a) Process b) Fixed c) Product d)Cellular 7 Batch Production produces the Quantity a) Minimum b) Less than 100 c) More than 10000 d) As per order 8 Automation with little human touch is known as a) Automation b)Autonomation c)Semi worker d)Manual work 9 Retrieval is also known as a.Recovery b. Get back c. Variant d. All 10Process planning is necessary for a. Planning b. Scheduling c. Planning and scheduling d. None

Answers: 1.c 2.c 3.b 4.d 5.c 6.b 7.d 8.b 9.a 10.c

Fill in the blanks questions with answers

1. _ _ _ _ _ _ _ _ can be defined as computer based system for planning, scheduling and controlling materials resources and supporting activities needed to meet the MPS :->Manufacturing resource planning 2. _ _ _ _ _ _ _ is a computational technique that converts the Master schedule for end products intoa detailed schedule for raw materials and components used in end products. :->Material Requirement planning 3. _ _ _ _ _ _ is an approach to part family identification and machine cell formation :-> 4. _ _ _ _ contains data on current and future inventory status of each component. :->Inventory record file 5. 2nd and 3rd digits in MICLASS indicate :-> 6. 34 is represented with the following code in binary coded decimal system for NC programming :-> 7. 54 is represented with the following code in binary coded decimal system in NC programming :-> 8. A _ _ _ _ _ _ _ _ _ _ _ _ is a combination of machine moves resulting in a particular machiningfunction :-> 9. A hypothetical part for a given family which includes all of the design and manufacturingattributes of family is called :-> 10. A process plan that can be used by a family of component is called _ _ _ _ _ _ _ _ _ _ :->

Answers:

1. Manufacturing resource planning 2. Material Requirement planning 3. PFA 4. Inventory record file 5. Shape elements 6. 00110100 7. 01010100 8. Canned cycle 9. Composite part 10. Standard plan

UNIT-V Two marks of questions with answers

1. What is FMS?

FMS is a manufacturing system based on multi-operation machine tools, incorporating

(automatic part handling and storage).

2. What is Process planning?

Process planning consists of preparing a set of instructions that describe how to

fabricate a part or build an assembly which will satisfy engineering design specifications.

Process planning is the systematic determination of the methods by which product is to be

manufactured, economically and competitively.

3. Which is ideal state in computer based manufacturing applications?

Computer Integrated Manufacturing (CIM) is an ideal state in which computer based

manufacturing applications communicate information to coordinate design, planning and

manufacturing processes.

4. What is the role of process planning in CIM architecture?

The process planning function can ensure the profitability or non profitability of a part

being manufactured because of the myriad ways in which apart can be produced.

5. List the applications of FMSs.

Applications of FMS installations are in the following areas.

Machining

Assembly

Sheet-metal press-working

Forging

Plastic injection molding


1. Flexible manufacturing systems:

Group of processing stations inter connected by means of a automated material handling and

storage system, and controlled by an integrated computer system. The guided vehicles are used as

the materials handling system in the FMS. The vehicles deliver work from the staging area

(where work is placed on pallet fixtures, usually manually) to the individual workstations in the

system.

The vehicles also move work between stations in the manufacturing system. At a

workstation, the work is transferred from the vehicle platform into the work area of the station

(usually, the table of a machine tool) for processing. At the completion of processing by that

station a vehicle returns to pick up the work and transport it to the next area. AGV systems

provide a versatile material handling system to complement the flexibility of the FMS operation.

2. Typical Computer Functions in a FMS

NC part programming - development of NC programs for new parts introduced into the system

Production control - product mix, machine scheduling, and other planning

functions

NC program download - part program commands must be downloaded to

individual stations

Machine control - individual workstations require controls, usually CNC

Workpart control - monitor status of each workpart in the system, status of pallet

fixtures, orders on loading/unloading pallet fixtures

Tool management - tool inventory control, tool status relative to expected tool life,

tool changing and resharpening, and transport to and from tool grinding

Transport control - scheduling and control of work handling system

System management - compiles management reports on performance (utilization,

piece counts, production rates, etc.)

3. What are the steps followed for quality control

(i) Manual inspection method surrogated by 100% automated inspection.

(ii) Offline inspection performed later is replaced with online sensor systems to

accomplish inspection during or immediately after the manufacturing process.

(iii) Feedback control of the manufacturing operation in which process variable that

determines product quality are monitored rather than the product itself.

(iv) Statistical process control is ensured using software tools to track and analyze

the sensor measurement over time.

(v) Advanced inspection and sensor technologies, interfaced with computer based

systems to automate the operations of the sensor systems

(vi) The term inspection can be defined as the activity of examining the products,

its components, sub-assemblies, or materials out of which it is made, and to

determine whether they adhere to design specifications. The design

specifications are prescribed by the product designer.

4. Give short notes on CMM:

contact with the part and the measurements are recorded in manual drive CMM. The three

orthogonal slides are designed to be nearly frictionless to permit the probe to be free floating in

the x, y, and z-directions. A digital readout provides the measurements that the operator can

record either manually or with paper printout. Only operator is allowed to carry out

calculations on the data that includes the enumeration of the center and hole diameter.

Data processing and computational capability for performing the calculations that are

required to evaluate a given part feature are provided by a CMM with manual drive CMM with

computer-assisted data processing. The different types of data processing and computations

are ranging from simple conversions between US customary units and metric to more

complicated geometry calculations, such as determining the angle between two planes. The

probe is free floating and permits the operator to bring it into contact with the desired part

surfaces.

5. Write down the benefits of CIM:

1. Increased machine utilization

2. Reduced direct and indirect labor

3. Reduce mfg. lead time

4. Lower in process inventory

5. Scheduling flexibility

CIM refers to a production system that consists of:

1. A group of NC machines connected together by

2. An automated materials handling system

3. And operating under computer control


1. Give an detail account of Flexible manufacturing system and FMS components. Group of processing stations inter connected by means of a automated material handling

and storage system, and controlled by an integrated computer system.

The guided vehicles are used as the materials handling system in the FMS. The

vehicles deliver work from the staging area (where work is placed on pallet fixtures, usually

manually) to the individual workstations in the system. The vehicles also move work between

stations in the manufacturing system. At a workstation, the work is transferred from the vehicle

platform into the work area of the station (usually, the table of a machine tool) for processing. At

the completion of processing by that station a vehicle returns to pick up the work and transport

it to the next area. AGV systems provide a versatile material handling system to complement

the flexibility of the FMS operation.

A flexible manufacturing system is a configuration of processing workstations

interconnected with computer terminals that process the end-to-end manufacturing of a

product, from loading/unloading functions to machining and assembly to storing to quality

testing and data processing. The system can be programmed to run a batch of one set of

products in a particular quantity and then automatically switch over to another set of products.

The main benefit is the enhancement of production efficiency, whereby downtime is reduced

because the need to shut down the production line to set up for a different product is

eliminated. One disadvantage of FMS is its higher up-front cost and the time required to

carefully preplan the system specifications. Another possible drawback is the higher cost

associated with the need for specialized labor to run, monitor and maintain the FMS; however,

since the FMS is meant to increase production automation (i.e., reduce labor input), the result

is typically a net benefit in terms of cost. Common FMS layouts take the form of line, loop,

ladder, and open field.

FMScomponents

BASIC COMPONENTS OF FMS Workstations- They are typically CNC machine tools that perform machining operation on families of parts. Automated Material Handling and Storage system- They are used to transport work parts and subassembly partsbetween the processing stations, sometimes incorporating storage into function. The processing or assembly equipment used in an FMS depends on the type of work accomplished by the system.

In a system designed for machining operations, the principle types of processing station are CNC machine tools. However, the FMS concept is also applicable to various other processes as well. Following are the types of workstations typically found in an FMS.

Load/Unload Stations. The load/unload station is the physical interface between the FMS and the rest of the factory. Raw work-parts enter the system at this point, and finished parts exit the system from here. Loading and unloading can be accomplished either manually or by automated handling systems. Manual loading and unloading is prevalent in most FMSs today. The load/unload station should be ergonomically designed to permit convenient and safe movement of work parts. For parts that are too heavy to lift by the operator, mechanized cranes and other handling devices are installed to assist the operator.

A certain level of cleanliness must be maintained at the workplace. and air hoses or other washing facilities are often required to flush away chips and ensure clean mounting and locating points. The station is often raised slightly above floor level using an open-grid platform to permit chips and cutting fluid to drop through the openings for subsequent recycling or disposal

2. Write and explain types of FMS.

TYPES OF FMS

DEPENDING UPON KINDS OF OPERATION

Processing operation. It performs some activities on a given job. Such activities

convert the job from one shape to another continuous up to the final product. It enhances significance by altering the geometry, features or appearance of the initial materia

comprises an assembly of two or more parts to make a new component which is called an assembly/subassembly. The subassemblies which are joined permanently use processes like welding, brazing, soldering , adhesive bonding, ri BASED ON NUMBER OF MACHINES

performing unattended operations within a time period lengthier than one complete machine cycle. It is skilful of dispensing various part mix, reacting to fluctuations in manufacture plan, and inviting introduction of a part as a new entry. It is a sequence dependent production manufacturing cell (FMC). It entails two or three dispensing workstations and a material handling system. The material handling system is linked to a load/unload station. It is a simultaneous production

(typically CNC machining centers or turning centers) connected mechanically by a common part handling system and automatically by a distributed computer system. It also includes non-processing work stations that support production but do not directly participate in it e.g., part / pallet washing stations, co-ordinate measuring machines. These features significantly differentiate it from Flexible

3. What is Computer Aided Quality Control or CAQC? The use of the computers for quality control of the product is called as the computer aided

quality control or CAQC. The two major parts of quality control are inspection and testing, which are traditionally performed manually with the help of gages, measuring devices and the testing apparatus. The two major parts of computer aided quality control are computer aided inspection (CAI) and computer aided testing (CAT). CAI and CAT are performed by using the latest computer automation and sensor technology. CAI and CAT are the standalone systems and without them the full potential of CAQC cannot be achieved.

The main objectives of the CAQC are to improve the quality of the product, increase the productivity in the inspection process and reduce the lead times in manufacturing. The implementation of CAQC in the company results in the major change in the way the process of quality control is carried out in the company.

Traditionally, quality control is carried out using manual inspection methods. It is a system in which standards are maintained on manufactured products through testing a sample of the items made against the original specification. Because of the fact it is manual, quality control can be a time-consuming and precise procedure that is open to human error. On occasion it can cause delays to the

-letter acronym essentially stands for - CAQ.

Computer-aided quality assurance is when computers are used to inspect and test products that are being manufactured. It is an engineering application that can oversee the operations of machinery and ensure everything is being produced as required.

It allows for a digital inspection of the quality of the products being produced. This includes measuring the equipment and its management/handling, producing a vendor rating, conducting a goods inward inspection, creating an attribute chart, putting in place statistical process control (SPC) and producing necessary documentation.Computer-aided quality assurance can also ensure a failure mode and effects analysis, otherwise known as FMEA, is put into action. Additionally, it can allow for advanced product quality planning and a dimensional tolerance stack-up analysis on computer-aided design models using the product and manufacturing information.

On top of this, it also encompasses a computer-aided inspection with coordinate-measuring machines and can compare data that has been gathered through the 3D scanning of the physical elements of computer-aided design (CAD) models.

4. Draw and explain working of CMM. In the world of digital manufacturing, where machines are capable of making parts to micron accuracies, being able to measure precisely and reliably is essential to qualifying every part that we make. take a closer look at one of our important measurement tools, the CMM, and how it works for you. At its most basic a coordinate is a point, a fixed singular location in three-dimensional space. A series of points can be used to define the parameters of a complex shape. Therefore a coordinate measuring machine (CMM) is any device that is able to collect this set of points for a given object and to do so with an acceptable degree of accuracy and repeatability. The foundation of the system is just that: a heavy base plate or table which serves as the foundation for an object placed on it to be measured. This is often a massive slab of granite or some other dense material that is stable, rigid, immune to fluctuations caused by the environment, and ground with a very flat top face.

To this table is mounted a moveable bridge or gantry. Vertical posts support a horizontal beam, and on this beam will be suspended another vertical column that holds the measuring probe. The bridge or gantry is able to move along the X-axis. The vertical spindle can move along the bridge thus defining the Y axis. And the probe on the vertical column can move up and down which defines the Z-axis over the table.

At the end of the spindle is the probe. There are different technologies available that can be used as a probe, partly depending on the objects to be measured and the degree of accuracy required. In our case, a precise sphere of ruby is mounted on the tip of the stylus.

Finally, the tip of the probe communicates its information to a computer which interprets the data with specialized software to create a 3D map of the part in question from the cumulative set of points.The exact size and position of the tip must be precisely known in advance to establish the

ce it is a hard substance that does not fluctuate in size due to temperature or humidity. The tip is mounted on a spring-loaded stylus. That stylus in turn has an angular rotation of 105° and a circular rotation of 360°.

As a result, the entire machine is considered a 5-axis CMM. The stylus is connected to exquisitely sensitive electronics that detect even the slightest deviation in electrical resistance coming from the probe. Each time the spherical tip contacts a solid object and is forced to deflect, that generates an electrical pulse which is sent to the computer which maps out a point on our imaginary X-Y-Z space. Hundreds or thousands of such points are collected, depending on the geometry and size of the part.

5. Draw and explain CIM Computer-integrated manufacturing (CIM) is themanufacturing approach of using computers to control the entire production process. This integration allows individual processes to exchange information with each other and initiate actions.

he integration of the total manufacturing enterprise through the use of

integrated systems and data communications coupled with new managerial philosophies that improve organizational -integrated manufacturing (CIM)is the manufacturing approach of using computers to control the entire production process. This integration allows individual processes to exchange information with each other and initiate actions. It is a way of thinking and solving problems. CIM is not a product that can be purchased and installed. It is the use of integrated systems and data communications coupled with new managerial philosophies. CIM is the integration of all enterprise operations and activities around a common corporate data repository. What is CIM?

Decrease in work-in process inventory Increase in manufacturing productivity Shorter customer lead time Lower total cost Improved competitiveness Greater flexibility and responsiveness Improved schedule performance Reduced inventory levels Shorter vendor lead time Shorter flow time Shorter time to market with new products Improved quality Improved customer service Potential Benefits of CIM

Better product quality, reduction of scrap 20-50%. Increase of productivity by 40-70%; Reduction of the in-shop time of a part by 30-60%; Reduction of design costs by 15-30%; Role of Computer in Manufacturing The computer has had a substantial impact on almost all activities of a factory.The operation of a CIM system gives the user substantial benefits: CIM is an example of the implementation of Information and Communication Technologies(ICTs)in manufacturing. Algorithms for uniting the data processing component with the sensor/modification component. Mechanisms for sensing state and modifying processes; Means for data storage, retrieval, manipulation and presentation; Manufacturing Method As a method of manufacturing, three components distinguish CIM from other manufacturing methodologies: CIM & Production Control System Process control: 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. Data integrity: 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. 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 (automated guided vehicles), even differing lengths of time for charging the batteries may cause problems. Key challenges There are three major challenges for the development of a smoothly operating computer-integrated manufacturing system: CAPP (Computer-Aided Process Planning) is the use of computer technology to aid in the process planning of apart or product, in manufacturing. CAM (Computer-Aided Manufacturing) is the use of computer software to control machine tools and related machinery in the manufacturing of work pieces. CAE (Computer-Aided Engineering) is the broad usage of computer software to aid in engineering tasks . CAD (Computer-Aided Design) involves the use of computers to create design drawings and product models. Subsystems in computer-integrated manufacturing

Multiple choice questions with answers 1 Flexible manufacturing systems (FMS) are reported to have a number of benefits. Which is NOT a reported benefit of FMS?

a) More flexible than the manufacturing systems they replace b) Lead time and throughput time reduction c) Increased quality d) Increased utilisation

2. Which materials-processing technology gives the advantage of precision, accuracy and optimum use of cutting tools, which maximise their life and higher labour productivity?

a) Computer-integrated manufacturing (CIM) b) Flexible manufacturing systems (FMS) c) Industrial robots d) NC (and CNC) machine tools

3. Before automating solely in search of cost savings, which one of the following is NOT a valid consideration:

a) Is it worth getting rid of the human potential along with its cost? b) Can the technology perform the task better (in a broader sense) or safer than a human? c) What support activities does the technology need in order to function effectively? d) Which is the most appropriate technology?

4. What do Flexible Manufacturing systems (FMS) do?

a) Co-ordinates the whole process of manufacturing and manufactures a part, component or product

b) Completely manufactures a range of components without significant human intervention during the processing

c) Moves materials between operations d) Moves and manipulates products, parts or tolls

5. Technology that is peripheral to the actual creation of goods and services is sometimes called:

a) Complementary process technology b) Indirect process technology c) Focused process technology d) Direct process technology

6. Which of the following is not true of computer numerically controlled (CNC) machines?

a) They give more accuracy and precision to the process. b) They can give better productivity to the process. c) They can eliminate operator error. d)

7. What classification is given to robots which grip tools, for example, in various types of metalworking operations, joining of materials, and surface treatment.

a) Process robots b) Assembly robots c) Tooling robots d) Handling robots

8. What is the name of a system which brings together several technologies into a coherent system?

a) Portable manufacturing systems b) Focused integration systems c) Automated integration systems d) Flexible manufacturing systems

9. Which of the following process technologies is associated with low volume and high variety?

a) Dedicated systems b) Flexible transfer lines c) CNC Machines

d) Flexible manufacturing systems 10.Which of the following is not an advantage of industrial robots?

a) Can be used in hazardous conditions. b) Gives greater accuracy and repeatability. c) Can be used in hazardous conditions. d) Flexibility in routing.

Answers:

1) a 2)d 3)d 4)b 5)b 6)d 7)a 8)d 9)c 10)d

Fill in the blanks questions with answers

1. _ _ _ _ _ _ _ _ _ _ involves the automatic generation of process plan or (route sheet) tomanufacture the part

2. _ _ _ _ _ _ _ _ _ _ _ _ _ _ is designed to produce a limited variety of parts 3. _ _ _ _ _ _ _ _ _ _ _ _ _ is a method for identifying part families and associated machine groupingsthat uses information continued on production route sheets 4. _ _ _ _ _ _ _ _ _ _ _ _ _systems are designed to fill the gap between high production transfer linesand low production NC Machines 5. _ _ _ _ _ _ layout type is generally appropriate for processing a large family of parts 6. _ _ _ _ _ _ _ _ _ _ _ _ is a collection of parts which are similar either because of geometric shapeand similar manufacturing operations 7. _ _ _ _ _ _ _ _ _ _ _ _ is used to compute the raw material and component requirements for endproducts listed in Master schedule 8. _ _ _ _ _ _ _ _ _ _ _ _ storage system used for batch and job shop production 9. _ _ _ _ _ _ _ _ _ _ _ _file contains the list of work stations through which each work part must beprocessed in CIM. 10. _ _ _ _ _ _ _ _ _ _ _ station is, where loads are transferred into and out of AS/RS

Answers 1) CAPP 2) FMS 3) Production flow Analysis 4) FMS 5) Open Field 6) Part family 7) Bill of materials file 8) WIP 9) Routing File 10) Pick-and-deposit

14. assignment topics with materials unit-i...

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