production management report
TRANSCRIPT
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A
REPORT
ON
PRODUCTION MANAGEMENT
SUBMITTED
IN PARTIAL FULFILLMENT
FOR THE AWARD OF THE DEGREE OF
BACHELOR OF TECHNOLOGYIN
DEPARTMENT OF ELECTRONICS & COMMUNICATION
ENGINEERING
Submitted to: - Submitted by: -
Ms. Kiran Raghuvanshi, Dhruvin Shukla,
Lect., CSE Dept. B.Tech. VIII sem.
DEPARTMENT OF ELECTRONICS & COMMUNICATION ENGINEERING
MARUDHAR ENGINEERING COLLEGE, BIKANER
RAJASTHAN TECHNICAL UNIVERSITY2011-12
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PREFACE
Production/operations management is the process, which combines and transforms various
resources used in the production/operations subsystem of the organization into value added
product/services in a controlled manner as per the policies of the organization. Therefore, it is
that part of an organization, which is concerned with the transformation of a range of inputs
into the required (products/services) having the requisite quality level.
The set of interrelated management activities, which are involved in manufacturing certain
products, is called as production management. If the same concept is extended to services
management, then the corresponding set of management activities is called as operations
management.
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Contents
S.No. Chapter Page No.
1. INTRODUCTION 01
2. CONCEPT OF PRODUCTION 03
3. PRODUCTION SYSTEM 05
4. CLASSIFICATION OF PRODUCTION SYSTEM 05
5. PRODUCTION MANAGEMENT 11
6. OPERATING SYSTEM 12
7. OPERATIONS MANAGEMENT 14
8. MANAGING GLOBAL OPERATIONS 18
9. SCOPE OF PRODUCTION AND OPERATIONS 20
10. QUALITY CONTROL 24
11. KANBAN 29
12. JIT 39
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Production management
INTRODUCTION
Production/operations management is the process, which combines and transforms various
resources used in the production/operations subsystem of the organization into value added
product/services in a controlled manner as per the policies of the organization. Therefore, it is
that part of an organization, which is concerned with the transformation of a range of inputs
into the required (products/services) having the requisite quality level.
The set of interrelated management activities, which are involved in manufacturing certain
products, is called as production management. If the same concept is extended to servicesmanagement, then the corresponding set of management activities is called as operations
management.
HISTORICAL EVOLUTION OF PRODUCTION AND OPERATIONS
MANAGEMENT
For over two centuries operations and production management has been recognised as an
important factor in a countrys economic growth.
The traditional view of manufacturing management began in eighteenth century when Adam
Smith recognised the economic benefits of specialisation of labour. He recommended
breaking of jobs down into subtasks and recognises workers to specialised tasks in which
they wouldbecome highly skilled and efficient. In the early twentieth century, F.W. Taylor
implemented Smiths theories and developed scientific management. From then till 1930,
many techniqueswere developed prevailing the traditional view. Brief information about the
contributions tomanufacturing management is shown in the Table 1.1.
TABLE 1.1 Historical summary of operations management
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Date Contribution Contributor
1776 Specialization of labour in manufacturing Adam Smith
1799 Interchangeable parts, cost accounting Eli Whitney and others
1832 Division of labour by skill; assignment of jobs
by skill; basics of time study
Charles Babbage
1900 Scientific management time study and work
study developed; dividing planning and doing
of work
Frederick W. Taylor
1900 Motion of study of jobs Frank B. Gilbreth
1901 Scheduling techniques for employees,
machines jobs in manufacturing
Henry L. Gantt
1915 Economic lot sizes for inventory control F.W. Harris
1927 Human relations; the Hawthorne studies Elton Mayo
1931 Statistical inference applied to product quality:
quality control charts
W.A. Shewart
1935 Statistical sampling applied to quality control:
inspection sampling plans
H.F. Dodge & H.G. Roming
1940 Operations research applications in World WarII
P.M. Blacker and others.
1946 Digital computer John Mauchlly and
J.P. Eckert
1947 Linear programming G.B. Dantzig, Williams &
others
1950 Mathematical programming, on-linear and
stochastic processes
A. Charnes, W.W. Cooper &
others
1951 Commercial digital computer: large-scale
computations available.
Sperry Univac
1960 Organizational behaviour: continued study of
people at work
L. Cummings, L. Porter
1970 Integrating operations into overall strategy and
policy, Computer applications to
manufacturing, Scheduling and control,
Material requirement planning (MRP)
W. Skinner J. Orlicky and G.
Wright
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1980 Quality and productivity applications from
Japan: robotics, CAD-CAM
W.E. Deming and
J. Juran.
Production management becomes the acceptable term from 1930s to 1950s. As F.W.
Taylors works become more widely known, managers developed techniques that focused on
economic efficiency in manufacturing. Workers were studied in great detail to eliminate
wasteful efforts and achieve greater efficiency. At the same time, psychologists, socialists
and other social scientists began to study people and human behaviour in the working
environment. In addition, economists, mathematicians, and computer socialists contributed
newer, more sophisticated analytical approaches.
With the 1970s emerges two distinct changes in our views. The most obvious of these,
reflected in the new name operations management was a shift in the service and
manufacturing sectors of the economy. As service sector became more prominent, the change
from production to operations emphasized the broadening of our field to service
organizations. The second, more suitable change was the beginning of an emphasis on
synthesis, rather than just analysis, in management practices.
CONCEPT OF PRODUCTION
Production function is that part of an organization, which is concerned with the
transformation of a range of inputs into the required outputs (products) having the requisite
quality level.
Production is defined as the step-by-step conversion of one form of material into another
form through chemical or mechanical process to create or enhance the utility of the product
to the user. Thus production is a value addition process. At each stage ofprocessing, there
will be value addition.
Edwood Buffa defines production as a process by which goods and services are created.
Some examples of production are: manufacturing custom-made products like, boilers with a
specific capacity, constructing flats, some structural fabrication works for selected customers,
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etc., and manufacturing standardized products like, car, bus, motor cycle, radio, television,
etc.
PRODUCTION SYSTEM
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The production system of an organization is that part, which produces products of an
organization. It is that activity whereby resources, flowing within a defined system, are
combined and transformed in a controlled manner to add value in accordance with the
policies communicated by management. A simplified production system is shown above.
The production system has the following characteristics:
1. Production is an organized activity, so every production system has an objective.
2. The system transforms the various inputs to useful outputs.
3. It does not operate in isolation from the other organization system.
4. There exists a feedback about the activities, which is essential to control and improve
system performance.
Classification of Production System
Production systems can be classified as Job Shop, Batch, Mass and Continuous Production
systems.
JOB SHOP PRODUCTION
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Job shop production are characterised by manufacturing of one or few quantity of products
designed and produced as per the specification of customers within prefixed time and cost.
The distinguishing feature of this is low volume and high variety of products.
A job shop comprises of general purpose machines arranged into different departments. Each
job demands unique technological requirements, demands processing on machines in a
certain sequence.
Characteristics
The Job-shop production system is followed when there is:
1. High variety of products and low volume.
2. Use of general purpose machines and facilities.
3. Highly skilled operators who can take up each job as a challenge because of uniqueness.
4. Large inventory of materials, tools, parts.
5. Detailed planning is essential for sequencing the requirements of each product, capacities
for each work centre and order priorities.
Advantages
Following are the advantages of job shop production:
1. Because of general purpose machines and facilities variety of products can be produced.
2. Operators will become more skilled and competent, as each job gives them learning
opportunities.
3. Full potential of operators can be utilised.
4. Opportunity exists for creative methods and innovative ideas.
Limitations
Following are the limitations of job shop production:
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1. Higher cost due to frequent set up changes.
2. Higher level of inventory at all levels and hence higher inventory cost.
3. Production planning is complicated.
4. Larger space requirements.
BATCH PRODUCTION
Batch production is defined by American Production and Inventory Control Society (APICS)
as a form of manufacturing in which the job passes through the functional departments in
lots or batches and each lot may have a different routing. It is characterised by themanufacture of limited number of products produced at regular intervals and stocked
awaiting sales.
Characteristics
Batch production system is used under the following circumstances:
1. When there is shorter production runs.
2. When plant and machinery are flexible.
3. When plant and machinery set up is used for the production of item in a batch and change
of set up is required for processing the next batch.
4. When manufacturing lead time and cost are lower as compared to job order production.
Advantages
Following are the advantages of batch production:
1. Better utilisation of plant and machinery.
2. Promotes functional specialisation.
3. Cost per unit is lower as compared to job order production.
4. Lower investment in plant and machinery.5. Flexibility to accommodate and process number of products.
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6. Job satisfaction exists for operators.
Limitations
Following are the limitations of batch production:
1. Material handling is complex because of irregular and longer flows.
2. Production planning and control is complex.
3. Work in process inventory is higher compared to continuous production.
4. Higher set up costs due to frequent changes in set up.
MASS PRODUCTION
Manufacture of discrete parts or assemblies using a continuous process are called mass
production. This production system is justified by very large volume of production. The
machines are arranged in a line or product layout. Product and process standardisation exists
and all outputs follow the same path.
Characteristics
Mass production is used under the following circumstances:
1. Standardisation of product and process sequence.
2. Dedicated special purpose machines having higher production capacities and output rates.
3. Large volume of products.
4. Shorter cycle time of production.
5. Lower in process inventory.
6. Perfectly balanced production lines.
7. Flow of materials, components and parts is continuous and without any back tracking.
8. Production planning and control is easy.
9. Material handling can be completely automatic.
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Advantages
Following are the advantages of mass production:
1. Higher rate of production with reduced cycle time.
2. Higher capacity utilisation due to line balancing.
3. Less skilled operators are required.
4. Low process inventory.
5. Manufacturing cost per unit is low.
Limitations
Following are the limitations of mass production:
1. Breakdown of one machine will stop an entire production line.
2. Line layout needs major change with the changes in the product design.
3. High investment in production facilities.
4. The cycle time is determined by the slowest operation.
CONTINUOUS PRODUCTION
Production facilities are arranged as per the sequence of production operations from the first
operations to the finished product. The items are made to flow through the sequence of
operations through material handling devices such as conveyors, transfer devices, etc.
Characteristics
Continuous production is used under the following circumstances:
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1. Dedicated plant and equipment with zero flexibility.
2. Material handling is fully automated.
3. Process follows a predetermined sequence of operations.
4. Component materials cannot be readily identified with final product.
5. Planning and scheduling is a routine action.
Advantages
Following are the advantages of continuous production:
1. Standardisation of product and process sequence.
2. Higher rate of production with reduced cycle time.
3. Higher capacity utilisation due to line balancing.
4. Manpower is not required for material handling as it is completely automatic.
5. Person with limited skills can be used on the production line.
6. Unit cost is lower due to high volume of production.
Limitations
Following are the limitations of continuous production:
1. Flexibility to accommodate and process number of products does not exist.
2. Very high investment for setting flow lines.
3. Product differentiation is limited.
PRODUCTION MANAGEMENT
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Production management is a process of planning, organizing, directing and controlling the
activities of the production function. It combines and transforms various resources used in the
production subsystem of the organization into value added product in a controlled manner as
per the policies of the organization.
E.S. Buffa defines production management as, Production management deals with
decision making related to production processes so that the resulting goods or services are
produced according to specifications, in the amount and by the schedule demanded and out
of minimum cost.
Objectives of Production Management
The objective of the production management is to produce goods services of right quality
and quantity at the right time and right manufacturing cost.
1. RIGHT QUALITY
The quality of product is established based upon the customers needs. The rightquality is not necessarily best quality. It is determined by the cost of the product and
the technical characteristic as suited to the specific requirements.
2. RIGHT QUANTITYThe manufacturing organization should produce the products in right number. If they
are produced in excess of demand the capital will block up in the form of inventory
and if the quantity is produced in short of demand, leads to shortage of products.
3. RIGHT TIME
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Timeliness of delivery is one of the important parameter to judge the effectiveness of
production department. So, the production department has to make the optimal
utilization of input resources to achieve its objective.
4. RIGHT MANUFACTURING COSTManufacturing costs are established before the product is actually manufactured.
Hence, all attempts should be made to produce the products at pre-established cost, so
as to reduce the variation between actual and the standard (pre-established) cost.
OPERATING SYSTEM
Operating system converts inputs in order to provide outputs which are required by a
customer. It converts physical resources into outputs, the function of which is to satisfy
customer wants i.e., to provide some utility for the customer. In some of the organization the
product is a physical good (hotels) while in others it is a service (hospitals). Bus and taxi
services, tailors, hospital and builders are the examples of an operating system.
Everett E. Adam & Ronald J. Ebert define operating system as, An operating system (
function) of an organization is the part of an organization that produces the organizations
physical goods and services.
Ray Wilddefines operating system as, An operating system is a configuration of resources
combined for the provision of goods or services.
Concept of Operations
An operation is defined in terms of the mission it serves for the organization, technology it
employs and the human and managerial processes it involves. Operations in an organization
can be categorized into manufacturing operations and service operations. Manufacturing
operations is a conversion process that includes manufacturing yields a tangible output: a
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product, whereas, a conversion process that includes service yields an intangible output: a
deed, a performance, an effort.
Distinction between Manufacturing Operations and Service Operations
Following characteristics can be considered for distinguishing manufacturing operations with
service operations:
1. Tangible/Intangible nature of output
2. Consumption of output
3. Nature of work (job)
4. Degree of customer contact
5. Customer participation in conversion
6. Measurement of performance.
Manufacturing is characterised by tangible outputs (products), outputs that customers
consume overtime, jobs that use less labour and more equipment, little customer contact, no
customer participation in the conversion process (in production), and sophisticated methods
for measuring production activities and resource consumption as product are made.
Service is characterised by intangible outputs, outputs that customers consumes immediately,
jobs that use more labour and less equipment, direct consumer contact, frequent customer
participation in the conversion process, and elementary methods for measuring conversion
activities and resource consumption. Some services are equipment based namely rail-road
services, telephone services and some are people based namely tax consultant services, hair
styling.
OPERATIONS MANAGEMENT
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A Framework for Managing Operations
Managing operations can be enclosed in a frame of general management function as shown in
Fig. 1.3. Operation managers are concerned with planning, organizing, and controlling the
activities which affect human behaviour through models.
PLANNING
Activities that establishes a course of action and guide future decision-making is planning.
The operations manager defines the objectives for the operations subsystem of the
organization, and the policies, and procedures for achieving the objectives. This stage
includes clarifying the role and focus of operations in the organizations overall strategy. It
also involves product planning, facility designing and using the conversion process.
ORGANIZING
Activities that establishes a structure of tasks and authority. Operation managers establish a
structure of roles and the flow of information within the operations subsystem. They
determine the activities required to achieve the goals and assign authority and responsibility
for carrying them out.
CONTROLLING
Activities that assure the actual performance in accordance with planned performance. To
ensure that the plans for the operations subsystems are accomplished, the operations manager
must exercise control by measuring actual outputs and comparing them to planned operations
management. Controlling costs, quality, and schedules are the important functions here.
BEHAVIOUR
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Operation managers are concerned with how their efforts to plan, organize, and control affect
human behaviour. They also want to know how the behaviour of subordinates can affect
managements planning, organizing, and controlling actions. Their interest lies in decision-making behaviour.
MODELS
As operation managers plan, organise, and control the conversion process, they encounter
many problems and must make many decisions. They can simplify their difficulties using
models like aggregate planning models for examining how best to use existing capacity in
short-term, break even analysis to identify break even volumes, linear programming and
computer simulation for capacity utilisation, decision tree analysis for long-term capacity
problem of facility expansion, simple median model for determining best locations of
facilities etc.
Objectives of Operations Management
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Objectives of operations management can be categorised into customer service and resource
utilisation.
CUSTOMER SERVICE
The first objective of operating systems is the customer serivce to the satisfaction of customer
wants. Therefore, customer service is a key objective of operations management. The
operating system must provide something to a specification which can satisfy the customer in
terms of cost and timing. Thus, primary objective can be satisfied by providing the right
thing at a right price at the right time.
These aspects of customer servicespecification, cost and timingare described for four
functions in Table 1.2. They are the principal sources of customer satisfaction and must,
therefore, be the principal dimension of the customer service objective for operations
managers.
Generally an organization will aim reliably and consistently to achieve certain standards andoperations manager will be influential in attempting to achieve these standards. Hence, this
objective will influence the operations managers decisions to achieve the required customer
service.
RESOURCE UTILISATION
Another major objective of operating systems is to utilise resources for the satisfaction of
customer wants effectively, i.e., customer service must be provided with the achievement of
effective operations through efficient use of resources. Inefficient use of resources or
inadequate customer service leads to commercial failure of an operating system.
Operations management is concerned essentially with the utilisation of resources, i.e.,
obtaining maximum effect from resources or minimising their loss, under utilisation or waste.
The extent of the utilisation of the resources potential might be expressed in terms of theproportion of available time used or occupied, space utilisation, levels of activity, etc. Each
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measure indicates the extent to which the potential or capacity of such resources is utilised.
This is referred as the objective of resource utilisation.
Operations management is also concerned with the achievement of both satisfactory customer
service and resource utilisation. An improvement in one will often give rise to deterioration
in the other. Often both cannot be maximised, and hence a satisfactory performance must be
achieved on both objectives. All the activities of operations management must be tackled
with these two objectives in mind, and many of the problems will be faced by operations
managers because of this conflict. Hence, operations managers must attempt to balance these
basic objectives.
Table 1.3 summarises the twin objectives of operations management. The type of balance
established both between and within these basic objectives will be influenced by market
considerations, competitions, the strengths and weaknesses of the organization, etc. Hence,
the operations managers should make a contribution when these objectives are set.
TABLE 1.3 The twin objectives of operations management
The customer service objective. The resource utilisation objective.
To provide agreed/adequate levels of customer
service (and hence customer satisfaction) by
providing goods or services with the right
specification, at the right cost and at the right
time.
To achieve adequate levels of resource
utilisation (or productivity) e.g., to achieve
agreed levels of utilisation of materials,
machines and labour.
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TABLE 1.2 Aspects of customer service
Principal
functionPrimary considerations Other considerations
Manufacture Goods of a given, requested or
acceptable specification
Cost, i.e., purchase price or cost of
obtaining goods.
Timing, i.e., delivery delay from
order or request
to receipt of goods.
Transport Management of a given, requested or
acceptable specification
Cost, i.e., cost of movements.
Timing, i.e.,
1. Duration or time to move.
2. Wait or delay from requesting to
its commencement.
Supply Goods of a given, requested or
acceptable specification
Cost, i.e., purchase price or cost of
obtaining goods.
Timing, i.e., delivery delay from
order or request
to receipt of goods.
Service Service Treatment of a given,
requested or acceptable specification
Cost, i.e., cost of movements.
Timing, i.e.,
1. Duration or time required for
treatment.
2. Wait or delay from requesting
treatment to
its commencement.
MANAGING GLOBAL OPERATIONS
The term globalization describes businesses deployment of facilities and operations around
the world. Globalization can be defined as a process in which geographic distance becomes a
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factor of diminishing importance in the establishment and maintenance of cross border
economic, political and socio-cultural relations. It can also be defined as worldwide drive
toward a globalized economic system dominated by supranational corporate trade and
banking institutions that are not accountable to democratic processes or national
governments.
There are four developments, which have spurred the trend toward globalization. These are:
1. Improved transportation and communication technologies;
2. Opened financial systems;
3. Increased demand for imports; and
4. Reduced import quotas and other trade barriers.
When a firm sets up facilities abroad it involve some added complexities in its operation.
Global markets impose new standards on quality and time. Managers should not think about
domestic markets first and then global markets later, rather it could be think globally and act
locally. Also, they must have a good understanding of their competitors. Some other
important challenges of managing multinational operations include other languages and
customs, different management style, unfamiliar laws and regulations, and different costs.
Managing global operations would focus on the following key issues:
To acquire and properly utilize the following concepts and those related to globaloperations, supply chain, logistics, etc.
To associate global historical events to key drivers in global operations from differentperspectives.
To develop criteria for conceptualization and evaluation of different globaloperations.
To associate success and failure cases of global operations to political, social,economical and technological environments.
To envision trends in global operations. To develop an understanding of the world vision regardless of their country of origin,
residence or studies in a respectful way of perspectives of people from different races,
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studies, preferences, religion, politic affiliation, place of origin, etc.
SCOPE OF PRODUCTION AND OPERATIONS
MANAGEMENT
Production and operations management concern with the conversion of inputs into outputs,
using physical resources, so as to provide the desired utilities to the customer while meeting
the other organizational objectives of effectiveness, efficiency and adoptability. It
distinguishes itself from other functions such as personnel, marketing, finance, etc., by its
primary concern for conversionby using physical resources. Following are the activities
which are listed under production and operations management functions:
1. Location of facilities
2. Plant layouts and material handling
3. Product design
4. Process design
5. Production and planning control
6. Quality control
7. Materials management
8. Maintenance management.
LOCATION OF FACILITIES
Location of facilities for operations is a long-term capacity decision which involves a long
term commitment about the geographically static factors that affect a business organization. It
is an important strategic level decision-making for an organization. It deals with the questions
such as where our main operations should be based?
The selection of location is a key-decision as large investment is made in building plant and
machinery. An improper location of plant may lead to waste of all the investments made in
plant and machinery equipments. Hence, location of plant should be based on the companys
expansion plan and policy, diversification plan for the products, changing sources of raw
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materials and many other factors. The purpose of the location study is to find the optimal
location that will results in the greatest advantage to the organization.
PLANT LAYOUT AND MATERIAL HANDLING
Plant layout refers to the physical arrangement of facilities. It is the configuration of
departments, work centres and equipment in the conversion process. The overall objective of
the plant layout is to design a physical arrangement that meets the required output quality and
quantity most economically.
According toJames Moore, Plant layout is a plan of an optimum arrangement of facilities
including personnel, operating equipment, storage space, material handling equipments and
all other supporting services along with the design of best structure to contain all these
facilities.
Material Handling refers to the moving of materials from the store room to the machine
and from one machine to the next during the process of manufacture. It is also defined as the
art and science of moving, packing and storing of products in any form. It is a specialized
activity for a modern manufacturing concern, with 50 to 75% of the cost of production. This
cost can be reduced by proper section, operation and maintenance of material handling
devices. Material handling devices increases the output, improves quality, speeds up the
deliveries and decreases the cost of production. Hence, material handling is a prime
consideration in the designing new plant and several existing plants.
PRODUCT DESIGN
Product design deals with conversion of ideas into reality. Every business organization have
to design, develop and introduce new products as a survival and growth strategy. Developing
the new products and launching them in the market is the biggest challenge faced by the
organizations. The entire process of need identification to physical manufactures of product
involves three functions: marketing, product development, manufacturing. Product
development translates the needs of customers given by marketing into technical
specifications and designing the various features into the product to these specifications.
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Manufacturing has the responsibility of selecting the processes by which the product can be
manufactured. Product design and development provides link between marketing, customer
needs and expectations and the activities required to manufacture the product.
PROCESS DESIGN
Process design is a macroscopic decision-making of an overall process route for converting
the raw material into finished goods. These decisions encompass the selection of a process,
choice of technology, process flow analysis and layout of the facilities. Hence, the important
decisions in process design are to analyse the workflow for converting raw material into
finished product and to select the workstation for each included in the workflow.
PRODUCTION PLANNING AND CONTROL
Production planning and control can be defined as the process of planning the production in
advance, setting the exact route of each item, fixing the starting and finishing dates for each
item, to give production orders to shops and to follow up the progress of products according
to orders.
The principle of production planning and control lies in the statement First Plan Your Work
and then Work on Your Plan. Main functions of production planning and control includes
planning, routing, scheduling, dispatching and follow-up.
Planning is deciding in advance what to do, how to do it, when to do it and who is to do it.
Planning bridges the gap from where we are, to where we want to go. It makes it possible forthings to occur which would not otherwise happen.
Routing may be defined as the selection of path which each part of the product will follow,
which being transformed from raw material to finished products. Routing determines the
most advantageous path to be followed from department to department and machine to
machine till raw material gets its final shape.
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Scheduling determines the programme for the operations. Scheduling may be defined as the
fixation of time and date for each operation as well as it determines the sequence of
operations to be followed.
Dispatching is concerned with the starting the processes. It gives necessary authority so as to
start a particular work, which has already been planned under Routing and Scheduling.
Therefore, dispatching is release of orders and instruction for the starting of production for
any item in acceptance with the route sheet and schedule charts.
The function offollow-up is to report daily the progress of work in each shop in a prescribed
proforma and to investigate the causes of deviations from the planned performance.
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QUALITY CONTROL
Quality Control (QC) may be defined as a system that is used to maintain a desired level of
quality in a product or service. It is a systematic control of various factors that affect the
quality of the product. Quality control aims at prevention of defects at the source, relies on
effective feed back system and corrective action procedure.
Quality control can also be defined as that industrial management technique by means of
which product of uniform acceptable quality is manufactured. It is the entire collection of
activities which ensures that the operation will produce the optimum quality products at
minimum cost.
The main objectives of quality control are:
To improve the companies income by making the production more acceptable to thecustomers i.e., by providing long life, greater usefulness, maintainability, etc.
To reduce companies cost through reduction of losses due to defects. To achieve interchangeability of manufacture in large scale production. To produce optimal quality at reduced price. To ensure satisfaction of customers with productions or services or high quality level,
to build customer goodwill, confidence and reputation of manufacturer.
To make inspection prompt to ensure quality control. To check the variation during manufacturing.
MATERIALS MANAGEMENT
Materials management is that aspect of management function which is primarily concerned
with the acquisition, control and use of materials needed and flow of goods and services
connected with the production process having some predetermined objectives in view.
The main objectives of materials management are:
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To minimise material cost. To purchase, receive, transport and store materials efficiently and to reduce the related
cost.
To cut down costs through simplification, standardisation, value analysis, import
substitution, etc.
To trace new sources of supply and to develop cordial relations with them in order toensure continuous supply at reasonable rates
To reduce investment tied in the inventories for use in other productive purposes andto develop high inventory turnover ratios.
MAINTENANCE MANAGEMENT
In modern industry, equipment and machinery are a very important part of the total
productive effort. Therefore, their idleness or downtime becomes are very expensive. Hence,
it is very important that the plant machinery should be properly maintained.
The main objectives of maintenance management are:
1. To achieve minimum breakdown and to keep the plant in good working condition at the
lowest possible cost.
2. To keep the machines and other facilities in such a condition that permits them to be used
at their optimal capacity without interruption.
3. To ensure the availability of the machines, buildings and services required by other
sections of the factory for the performance of their functions at optimal return on investment.
WEGMANS FOOD MARKETS
Wegmans Food Markets, Inc., is one of the premier grocery chains in the United States.
Headquartered in Rochester, NY, Wegmans operates over 70 stores. The company employs
over23,000 people, and has annual sales of over Rs. 2.0 billion.
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Wegmans has a strong reputation for offering its customers high product quality and
excellent service. Through a combination of market research, trial and error, and listening to
its customers, Wegmans has evolved into a very successful organization. In fact, Wegmans is
so good at what it does that grocery chains all over the country send representatives to
Wegmans for a firsthand look at operations.
SUPERSTORES
Many of the companys stores are giant 100,000 square foot superstores, double or triple the
size of average supermarkets. A superstore typically employs from 500 to 600 people.
Individual stores differ somewhat in terms of actual size and some special features. Aside
from the features normally found in supermarkets, they generally have a large bakery Section
(each store bakes its own bread, rolls, cakes, pies, and pastries), and extra large produce
sections. They also offer film processing a complete pharmacy, a card shop and video rentals.
In-store floral shops range in size up to 800 square feet of space, and offer a wide variety of
fresh-cut flowers, flower arrangements, varies and plants. In-store card shops covers over
1000 square feet of floor of floor space. The bulk foods department provides customers with
the opportunity to select what quantities they desire from a vast array of foodstuffs and some
nonfood items.
Each store is a little different. Among the special features in some stores are a dry cleaning
department, a wokery, and a salad bar. Some feature a Market Cafe that has different food
stations, each devoted to preparing and serving a certain type of food. For example, onestation has pizza and other Italian specialties, and another oriental food. There are also being
a sandwich bar, a salad bar and a dessert station. Customers often wander among stations as
they decide what to order. In several affluent locations, customers can stop in on their way
home from work and choose from a selection of freshly prepared dinner entrees. Some stores
have a coffee shop section with tables and chairs where shoppers can enjoy regular or
specialty coffees and variety of tempting pastries.
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PRODUCE DEPARTMENT
The company prides itself on fresh produce. Produce is replenished as often as 12 times a
day. The larger stores have produce sections that are four to five times the size of a produce
section of an average supermarket. Wegmans offers locally grown produce a season.
Wegmans uses a farm to market system whereby some local growers deliver their produce
directly to individual stores, bypassing the main warehouse. That reduces the companys
inventory holding costs and gets the produce into the stores as quickly as possible. Growers
may use specially designed containers that go right onto the store floor instead of large bins.
This avoids the bruising that often occurs when fruits and vegetables are transferred from
bins to display shelves and the need to devote labor to transfer the produce to shelves.
MEAT DEPARTMENT
In addition to large display cases of both fresh and frozen meat products, many stores have a
full-service butcher shop that offers a variety of fresh meat products and where butchers are
available to provide customized cuts of meat for customers.
ORDERING
Each department handles its own ordering. Although sales records are available from records
of items scanned at the checkouts, they are not used directly for replenishing stock. Other
factors, such as pricing, special promotions, local circumstances must all be taken into
account. However, for seasonal periods, such as holidays, managers often check scanner
records to learn what past demand was during a comparable period.
The superstores typically receive one truckload of goods per day from the main warehouse.
During peak periods, a store may receive two truckloads from the main warehouse. The short
lead-time greatly reduce the length of the time an item might be out of stock, unless the main
warehouse is also out of stock.
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The company exercises strict control over suppliers, insisting on product quality and on-time
deliveries.
EMPLOYEES
The company recognises the value of good employees. It typically invests an average of
Rs.7000 to train each new employee. In addition to learning about stores operations, new
employees learn the importance of good customer service and how to provide it. The
employees are helpful, cheerfully answering customer questions or handling complaints.
Employees are motivated through a combination of compensation, profit sharing, and
benefits.
QUALITY
Quality and Customer satisfaction are utmost in the minds of Wegmans management and its
employees. Private label food items as well as name brands are regularly evaluated in test
kitchens, along with the potential new products. Managers are responsible for checking and
maintaining products and service quality in their departments. Moreover, employees are
encouraged to report problems to their managers.
If a customer is dissatisfied with an item and returns it, or even a portion of the item, the
customer is offered a choice of a replacement or a refund. If the item is a Wegmans brand
food item, it is then sent to the test kitchen to determine the cause of the problem. If the cause
can be determined, corrective action is taken.
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KANBAN
KANBAN is a model of economic production management which is used today by a great
number of well known companies all over the world. Its basic principles were developed a
long time ago by the Toyota group in Japan. The Japanese term KANBAN is interpreted as
a visual card or signal.
The core notion of lean production is the design of a valueadded process as a continuous
flow. However, there are always points in a value stream where continuous flow produc-tion
is not possible and must be replaced by production in lot sizes. The KANBAN system should
be used when cycle times are very long or very short, when workplaces are located at great
distances from each other, or when pro-cesses are highly unreliable.
KANBAN
reduces circulating inventory and finished goods. This, in turn, reduces capital lockupas well as any wasting activities which are associated with stocks;
limits the inventory so that set stocks cannot be exceeded; increases the flexibility with regard to varying customer requirements; simplifiesproduction management to a great extent. Actually, KANBAN doesnt even
need an EDP system. It only requires cards, scheduling boards and discipline.
The KANBAN Method
Owing to its analogue method of operation, KANBAN management is also called the
supermarket principle. Being an anonymous customer, a consumer removes preproduced
goods from the shelf. The operator of the supermarket refills the quantities removed. This
means for produc-tion: planning intervention is necessary only with regard to the quantity to
be kept and the time of ordering. This reduces scheduling and management activities in daily
work to a minimum. Processes are interrelated through a buffer inventory containing
produced parts that are provided by the supplier and removed by the customer.
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KANBAN replaces the conventional order management with consumption management by
forming an interconnected self-managing control loop from two series processes. The control
loop comprises a parts consuming process, that is the customer, and an upstream parts
producing process, that is the supplier. The KANBAN card is the ordering document.
Once the customer process receives the order for producing a product, it removes the
appropriate part from the buffer inventory. The resulting gap must be closed by the supplier
process. The production order is indicated on KANBAN cards attached to the parts or part
containers. When a part is removed from the buffer inventory, the pertinent card is delivered
to the supplier. The cards circulate in a control loop. This process is called card KANBAN.
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Global manufacturing enterprises continually strive to improve their respective
manufacturing operations to regain a competitive advantage particularly in the automotive
and computer industries. These industries are responding to the challenge of e-commerce and
customer ordering via the Internet by shifting to re-configurable manufacturing equipment
and a make-to-order environment. Traditional mass production manufacturing is not
particularly responsive to changing customer demands, for it relies on forecasting future
demand and scheduling the release of work into the system to meet expected demand. Mass
production systems often have excess inventory, higher WIP levels, and longer quoted lead-
times from order to delivery. In contrast, just-in-time production relies on actual demand
triggering the release of work into the system, and pulling work through the system to fill
the demand order. Just-in-time production is better able to respond to changing customer
demands, for as a production philosophy, it advocates producing the right products at the
right times and in the right amounts. Reconfigurable systems allow rapid and low-cost
changeovers to allocate production capacity as needed to the products that are desired.
Manufacturers are also moving toward modular subassemblies built off-line and delivered by
suppliers as needed. Thus, a fundamental understanding of pull manufacturing and assembly
systems is required to implement the make-to-order paradigm.
Industrial engineering undergraduate curriculums generally include a course on production
and operations analysis, in which just-in-time and lean manufacturing principles are
conceptually presented. Many students also take a course on simulation that covers a
simulation language, random number generation, input modeling, verification and validation
strategies, and output analysis techniques. However, there is little or no textbook material
available discussing modeling, control, and analysis of pull systems using simulation. This
paper attempts to address this deficiency, and can serve as a supplement for simulation and
production operations courses.
Simulation models are used in this paper to illustrate the mechanics of pulling within
systems, and give the reader a hands-on approach toward studying Kanban and CONWIP
pull systems. Spearman and Zazanis (1992) provide a more advanced discussion of push,
pull, and CONWIP production systems and present theoretical motivations for the improved
performance of pull systems over traditional push systems. They contribute analytical results
for the types of pull systems considered in this paper, and offer several conjectures that the
reader is encouraged to consider while studying the pull simulation models presented herein.
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(1) There is less congestion in pull systems.
(2) Pull systems are inherently easier to control than push systems but can be conceptually
more difficult to model.
(3) The benefits of a pull environment owe more to the fact that WIP is bounded than to the
practice of pulling everywhere.
PULL SYSTEMS: KANBAN AND CONWIP
Kanban, meaning card or marker in Japanese, is the more widely known and recognized
type of pull system. A Kanban pull system is sometimes referred to as the Toyota Production
System (just-in-time manufacturing using a Kanban pull system) (Monden 1981a). A Kanban
pull system uses card sets to tightly control work-in progress (WIP) between each pair of
workstations. Total system WIP is limited to the summation of the number of cards in each
card set. Production occurs at a workstation only if raw material is available and the material
has a card authorizing production. Material is pulled through the system only when it receives
card authorization to move. Figure 1 illustrates a serial Kanban system. Each Kanban card set
between workstations authorizes material to be pulled into the upstream workstation for
processing and delivery to the downstream workstation. For example, card set 2 (between
Workstations 1 and 2) authorizes an order in the paperwork queue (before Workstation 1) and
raw material to be released for processing at Workstation 1, and delivery to Workstation 2.
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In contrast, a CONWIP pull system uses a single global set of cards to control total WIP
anywhere in the system. Material enters a CONWIP system only when demand occurs, and
the raw material receives a card authorizing entrance; the same card authorizes the material to
move through the system and complete production. When the final product leaves the system,
the card is released, allowing new material to enter the system as new demand occurs. Notice
that WIP is not controlled at the individual workstation level in the CONWIP system. Total
WIP in the system is a constant (thus the name CONWIP), for the cards limit the total amount
of work that can be anywhere in the system. The Kanban system in Figure 1 pulls work
everywhere (between every pair of workstations), while the CONWIP system in Figure 2 only
pulls work at the beginning of the line. Notice that in both diagrams orders are kept in a
paperwork queue prior to Workstation 1 until the order and raw material receive a production
and material movement authorization card.
Once raw material is authorized to enter the CONWIP
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blackbox, the material flows freely as if it were in apush system. Inside the black box,
WIP naturally accumulates in front of the bottleneck station. CONWIP systems handle a mix
of parts having different bottlenecks with more ease than Kanban systems. If the bottleneck
shifts as the mix of parts changes, there may be an opportunity to reduce WIP by reducing the
total number of cards allocated for product flow. Conversely, cards may need to be added to
increase WIP and ensure a desired throughput. CONWIP systems are easy to manage, for
there is only one set of global cards that requires review and adjustment. Kanban systems are
more difficult to manage but more tightly control WIP, for card control of WIP is
implemented at the workstation level. If a product mix change shifts the bottleneck in a
Kanban system, the number of cards allocated to each card set may require adjustment to
ensure a desired throughput. In the simple four workstation example illustrated in Figure 1, if
the bottleneck shifts, three different sets of Kanban cards (controlling WIP before
Workstations 2, 3, and 4) must be inspected.
WHY CONTROL WIP?
Manufacturers have found several advantages in controlling WIP. A finite WIP capacity
limits the amount of material released into the system, allowing orders to stay on paperinstead of as physical material on the production floor. Production systems have a degree of
flexibility that is lost when large volumes of WIP are in the physical system. Keeping orders
on paper until actual production occurs facilitates execution of scheduling and design
changes. Scrapping product due to a design or engineering change can be costly, especially to
a company with large amounts of WIP in the system. By controlling WIP, the amount of
material that needs to be scrapped or reworked is reduced, and financial losses from sales of a
now inferior product are diminished.
A second advantage of WIP control is a reduction in cycle time variability. Referring to
Littles Law (WIP = Cycle Time * Arrival Rate), if the arrival rate is held constant, as the
level of WIP increases, the cycle time must also increase. Push systems allow the possibility
of large WIP buildups, causing high variability in cycle time plus increased costs in terms of
inventory buildup. Increased variability in cycle time forces companies to quote longer lead-
times in order to achieve the same level of customer service. Limiting WIP reduces the
variability in cycle time while allowing the pull system to still achieve the same throughput
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level with less WIP than a push system. To accurately quote a time from order to delivery in
a pull system, the time should include both the time that the order spends on paper and the
actual time in the physical production system.
SHOULD EVERY MANUFACTURING COMPANY USE PULL
SYSTEMS?
The next question to address is should pull systems be implemented in most manufacturing
facilities. Surprisingly, the answer is NO. The two types of pull systems respond slightly
differently to changes in volume and product mix. The major disadvantage for both types of
pull systems is that they require fairly steady product flow. Kanban is typically restricted to
repetitive manufacturing where material flows at a steady rate in a fixed path. Large
variations in volume or product mix destroy the flow and undermine the systems
performance goals. If there is too much WIP, the goal of minimizing WIP in the system is not
achieved, and financial flexibility in dealing with scheduling and engineering changes is lost.
If there is too little WIP, throughput goals cannot be attained. CONWIP, while still requiring
a relatively steady volume, is a little more resilient in handling changes in product mix. The
difference between their capabilities of handling product mixes has to do with the individual
products having different bottlenecks and how WIP is controlled within the system.Questions to consider when assessing whether a pull system should be adopted include:
How often do design, engineering and schedule changes occur?
What are the economic consequences of maintaining the current system compared to
converting to a pull system?
Can a pull system reduce overall lead-time compared to a push system?
Are suppliers reliable enough to support just-intime delivery of raw materials or
subcomponents?
Is the production system reliable, or does it suffer frequent breakdowns that stop
production?
Are labor and management committed to making the changes needed?
How often and how significantly does the product mix change?
In situations where a pull system is found to be acceptable for a facility, a decision of which
type of pull system to implement must be made. As discussed previously, the choice depends
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on the level of WIP control desired (at the individual workstation level, or a blackbox
system level).
SIMULATION MODELS OF KANBAN AND CONWIP PULL SYSTEMS
Simulation models have been developed in Arena 3.5 and tested in Arena 4.0 for the Kanban
and CONWIP systems in Figures 1 and 2 respectively (Marek, 2000). The reader is assumed
familiar with the basics of simulation programming and analysis. The code for these models
is presented in the following sections for the reader to obtain a hands-on feel for the
different pull mechanics in each system.
The serial manufacturing systems being modeled contain four workstations, and must
produce two types of products. The make-to-order production facility has reconfigurable
manufacturing equipment, allowing rapid and low cost changeovers to switch between
product types. The setup times for changing between product types are considered to be zero
on the assumption that the products are quite similar. This is a realistic assumption, for
production line designers are now examining the value of agile tooling, fixtures, and material
handling, so that any part in a general family may be produced on the line if the designed partfits within the lines production envelope. For this reason, product types are not batch
processed on a forecasted basis, but are processed on a first-come firstserve (FCFS) basis as
orders arrive. Product types are assigned from a discrete probability distribution for each
arriving order with 70% type 1 and 30% type 2. Process times at each workstation may
depend on product type. Machine breakdowns and supply chain failures are currently not
considered.
The variance reduction technique of Common Random Numbers (CRN) (Pegden, et al.,
1995) is employed to synchronize usage of random numbers in the Kanban and CONWIP
systems so that the systems are compared under similar conditions. Each system observes the
same sequence of arrivals of type 1 and type 2 jobs and uses the same processing times for
jobs at each workstation. This approach is often justified for scenario analysis whereby the
analyst seeks to compare two or more alternatives (systems) and control specified parameter
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sequences while permitting other system parameters to vary. By designing the various
simulation runs, the analyst can better distinguish the impact(s) of specific changes in the
scenarios.
Throughout the remainder of this paper, specific ARENA modeling constructs are used to
define the modeling approach. The ARENA SEEDS element controls the six random number
streams used (See Table 1). By using common random numbers, randomness in experimental
conditions is reduced, and any measured differences in the two systems are due to the pull
behavior and card control level used.
Stream Seed Purpose
1 2323 Job Inter-Arrival Times
2 4545 Workstation 1 Processing
Times
3 8080 Workstation 2 Processing
Times
4 8181 Workstation 3 Processing
Times
5 1717 Workstation 4 Processing
Times
6 1974 Job Type
The Arrival Rate and the Shifting Bottleneck
The arrival rate of orders is taken arbitrarily to be 1/54 orders per minute. This arrival rate is
of interest, for the paperwork queue (queue before Workstation 1) explodes if only part type 1
or part type 2 is processed. Considering product mix is important, for by construction, the
bottleneck also shifts if only one type of part is processed. If only part type 1 is processed,
Workstation 3 is the bottleneck; if part type 2 is processed, Workstation 4 is the bottleneck.
For the product mix as stated and orders processed FCFS, the system bottleneck is
Workstation 3, and the paperwork queue is relatively stable (does not explode).
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Bottleneck Determination
Bottleneck determination is straightforward for both types of serial pull systems. Ignoring
machine breakdowns, and assuming no scrap or rework occurs, the bottleneck is the
workstation with the highest utilization. Suppose that 24 cards are allotted for each Kanban
card set. After running the Kanban model for a replication length of 96000 minutes with a
warm-up of 64000 minutes, Workstation 3 can be verified to be the bottleneck, with 99.213%
utilization (compared to utilizations of 38.249%, 57.247%, and 81.421% at Workstations 1,
2, and 4 respectively). Similarly, if a total of 30 cards is allotted for the CONWIP system, and
the CONWIP model is run for a replication length of 96000 minutes with a warm-up of
64000 minutes, Workstation 3 is again the bottleneck with 99.23% utilization (compared toutilizations of 38.16%, 57.28%, and 81.44% at Workstations 1, 2, and 4 respectively).
Measuring Workstation Utilization
In the Kanban model, a card and workstation are seized simultaneously. As soon as
processing completes, the workstation is released. However, the current card is retained, until
the part receives the next card authorizing movement to the next workstation. The ARENASEIZERELEASE sequence allows a more accurate measure of workstation utilization for
Kanban pull systems. Each workstation processes only when authorized to do so, and is busy
only for the process time duration. In the CONWIP model, the workstation is seized when
available and released as soon as the processing time is complete. The SEIZE-RELEASE
pattern in the CONWIP system also yields an accurate measure of workstation utilization for
the CONWIP system.
One Card or Two Cards?
The Kanban pull model demonstrates a 1-card Kanban system with 24 cards assigned to
control WIP before each of Workstations 2, 3, and 4. The CONWIP pull model is also a 1-
card model, with a total of 30 cards allotted to control WIP. 1-card systems are the easiest to
understand and implement, and use the same card to authorize material movement and
production. 2-card systems are similar to 1- card systems, but use 2 different types of cards to
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control production and material movement separately. The codes can be modified
appropriately to implement a 2-card level of control.
Blocking After Service
Card control in a Kanban system can cause a workstation to become idle, even if it has raw
material to process. This idleness is due to blocking after service. The blocked workstation is
forced to stop production because there are no available cards to pull work from the current
workstation. Card control at the individual workstation level introduces an additional level of
dependence between the workstations. The simpler card control structure in CONWIP
systems does not introduce the additional workstation dependency nor cause blocking afterservice. Since a CONWIP system behaves as a push system inside the black box, each
workstation will continue to process work as long as there is work in the queue before it. WIP
will tend to accumulate in front of the bottleneck workstation. However, queue explosion
does not occur as in a push system, since card control limits total WIP.
JUST IN TIME
INTRODUCTION
Why Just-In-Time manufacturing when there are dozens of other manufacturing
philosophies from which a company may choose? Just-InTime (JIT) manufacturing distances
itself from the competition because no large capital outlays are required. Other methods
promote complexity, large overheads, automation, and other "state-of-the-art" technologies,
while JIT advocates simplifying and streamlining the existing manufacturing process.
Since World War II, traditional American companies have developed a way of doing business
that entails top management planning, re-planning, and more planning. Although some
planning is good, it ultimately adds no value to the end product. Customers want quality
products at competitive prices they couldn't care less how much planning was required to get
that product to them. By implementing JIT, much of the planning disappears and a large
portion of the remaining planning is entrusted to the shop floor personnel.
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The purpose of this text is to introduce basic JIT concepts and assure you that JIT can work in
your company. The transition to JIT often is not easy, but it is almost always rewarding. All
employees in the company - from top management to direct labor - must have a clear
understanding of the benefits that JIT offers to them and to their company. JIT is not a cure-
all for every manufacturing problem. But, if implemented properly, JIT is a no-cost or low-
cost method for improving your manufacturing process.
JIT PHILOSOPHY
The basis of Just-In-Time (JIT) is the concept of ideal production. It centers on the
elimination of waste in the whole manufacturing environment, from raw materials through
shipping. Just-In-Time is defined as "the production of the minimum number of different
units, in the smallest possible quantities, at the latest possible time, thereby eliminating the
need for inventory. Remember, JIT does not mean to produce on time, but to produce just in
time.
History of Just-In-Time
JIT is sometimes said to have been invented by Henry Ford because of his one-at-a-time
assembly line, circa 1913. This is an incorrect conclusion since Ford's system could handle
no variety and was designed for large volumes and large batch sizes of the same parts.
JIT was invented by Taiichi Ohno of Toyota shortly after World War II. Ohno's system was
designed to handle large or small volumes of a variety of parts. Many people are intimidated
by JIT because of its association with Japan. If these people take a broader look at JIT, they
will see that it is nothing more than good, common sense manufacturing.
Ohno and his associates came to America to study our manufacturing processes. They
determined that our system was much like the system that Japanese companies were using,
but Japanese companies could not afford waste in their systems due to the devastation to their
economy caused by World War II. While in America, Ohno learned much about America's
culture. One of his discoveries has transformed the world's perspective on manufacturing.
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From Supermarket To Shop Floor
Legend has it that Ohno got the idea for his manufacturing system from America's
supermarket system. Ohno learned the kanban (pull) system from our supermarket system in
which customers pulled items from the shelves to fill their shopping carts, thereby creating an
empty space on the shelf. The empty space is a signal for the stocker to replace that item. If
an item was not bought that day, there was no need to replace it. When item quantities
become low, that is the signal for the stockers to order more goods from their suppliers.
Customers are content to take just what they need, because they know that the goods will be
there the next time they need them.
To apply this concept to manufacturing, Ohno devised a system whereby the usage of parts is
determined by production rates Materials are pulled through the plant by usage or
consumption of the parts in final assembly. To obtain maximum results, Ohno decided to
move the machines closer together and form manufacturing cells.
The JIT system continued to evolve, with the central thrust being the elimination of waste.
Ohno's system has become a totally flexible system in which production rates are determined
by the end user rather than the producer.
What To Expect
While the prevailing view of JIT is that of an inventory control system, it is much more. JIT
is an operational philosophy which incorporates an improved inventory control system in
conjunction with other systems, such as:
A set-up time improvement system.
A maintenance improvement system.
A quality improvement system.
A productivity improvement system.
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A properly implemented JIT system should:
Produce products customers want.
Produce products only at the rate that customers want them.
Produce with perfect quality.
Produce instantly with zero unnecessary lead time.
Produce with no waste of labor, material, or equipment. Every move has a purpose and
there is no idle inventory.
An overview of JIT literature suggests that the steps or elements of the implementation
process generally (though not always) include the following:
Reductions in set-up time.
Utilization of a formal preventive maintenance program.
Utilization of quality circles.
Utilization of cellular manufacturing techniques.
Cross-training of employees.
Quality certification of suppliers.
Reductions in vendor lead time.
Reductions in lot sizes.
Sole sourcing.
Presence of one who "championed the cause of JIT within the firm.
Benefits touted as results of JIT implementation include:
Reductions in down time.
Reductions in inventory.
Reductions in scrap and re-work.
Reductions in workspace.
Increased inventory turns.
Increased labor utilization.
Increased equipment utilization.
Improved service to customers.
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VALUE-ADDED ANAlYSIS
Maybe you believe that your company is efficient enough and that the benefits of JIT are not
worth the frustration and stress associated with change. At this point you have a decision to
makeyou can adopt a new company motto such as Were no worse than anybody else, or
you can take positive steps toward improving the process. To strengthen the incentive for
change, companies should identify the inefficiencies (wastes) in their present manufacturing
processes.
To identify waste in your company, a value-added analysis should be performed. We must
always be aware that any activity that does not add value to a product is waste. There are
specific methods for performing a value-added analysis but we will use a simplified approach
for our purposes. Take a pad and pencil and go out on the shop floor. Pick a product and
follow it through the entire manufacturing process from raw materials to shipping. Note every
activity performed on the product. Do not get a routing slip to see how the process is
supposed to go, but accurately record the process including delays, transportation, inspection,
storage, etc. Figure 1-1 on the following page is a value-added analysis for a machined part.
UNDERSTANDING WASTE
Ask almost any shop floor employee the definition of inventory and the likely answer will be
you know all this stuff stacked up around here and all that stuff in the warehouse. Many
employees (and some supervisors and managers) do not understand that Work-In-Process
(WIP) is also inventory. Pure and simple inventory is waste. Another way to describe
inventory is money loaned out of a companys pocket that has yet to be repaid.
JIT is much more than a plan for decreasing inventory, it is a manufacturing philosophy for
eliminating waste. For our purposes, waste can be defined as something other than the
essential resources of people, machines, and material needed to add value to the product.
Anything else, such as inventory, scheduling, meetings, warehousing goods, management,
and moving stock can be considered wasteful because these actions do not directly add value
to the product. All waste cannot be purged from the system, however, we must strive toward
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that ideal goal. Above all it must be ever present in the attitudes of our manufacturing system
that cost without value is waste.
A typical company produces excess inventory with the idea that we can use this stuff when
the next order comes in." Routinely these parts are forgotten when the next order is placed.
Other than initial costs of the products, they are also paying for moving the product,
warehouse space, fork trucks, warehouse personnel, tracking the products, and moving the
products again, etc. One company that we visited was constantly plagued with the problem of
misplaced inventory. They had numerous storage bins, plus inventory was sometimes
temporarily placed on the shop floor in different places. More often than not, new parts
would be made when the internal customer needed the parts, because nobody knew the parts
already existed. Another company we visited wastes money on rust preventatives and the
time-consuming task of removing rust from parts in storage solely for the benefit of excess
inventory.
JIT AND QUALITY
The single most substantial ingredient of JIT is quality. It is impossible for JIT to be
successful until the company has drastically improved its attitude toward quality. In the
language of the Malcolm Baldrige National Quality Award, quality is a race with no finish
line." The ultimate aspiration is to satisfy all customers (internal and external) all the time.
The Wallace Company, a past winner of the Baldrige Award, installed a buzzer on the shop
floor that sounded anytime a customer called their customer service hot line. Instantly all
workers knew they had a dissatisfied customer. Can you imagine installing such a device in a
traditional manufacturing company?
What is Quality?
One of the great gurus of quality, Phil Crosby, says that companies often have a
misconception of quality. He says that the true definition of quality is meeting
requirementsnot an intuition for aesthetics, roundness, or perfectionbut something that
can be truly measured. If a Yugo (economy car of the the early 1970s) meets its customer's
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requirements as well as a Rolls Royce meets its customer's requirements, then it can be
argued that the Yugo is as much a quality car as a Rolls Royce.
Now that we understand what quality is and what it can do for us, how do we get quality?
The key is to obtain quality at the source. The sources for quality are the manufacturers and
vendors processes, machines, and operators. Contrary to traditional beliefs, the source of
quality is not the inspection bench.
Preventing Quality Problems
To dismantle the inspection bench mentality, we must take positive steps in prevention ofquality problems. Specific guidelines and rigorous procedures must be established. The steps
toward attaining a quality product are to first define the requirements, get the process under
control, and then keep the process under control.
Defining the Requirements
Many manufacturing companies do an inadequate job of defining quality requirements. If you
are looking at a part or a process, and say thats good enough then you have not sufficiently
defined your requirements. The real definition of quality is meeting both internal and external
customer requirements. Employees and vendors should have strict guidelines that distinguish
good parts (quality) from rework or rejected parts so 100 percent customer satisfaction can be
reached.
Let us look back at our ACME manufacturing example. The assembler had no specificrequirements for pressing the bearings into the wheel. He was told that the wheel must run
true. What is true? How much leeway does he have? Can the bearings be somewhat angled or
must they be exactly straight? The assembler should be supplied with strict criteria for quality
such as each bearing should be pressed into the wheel at a perpendicular angle plus or minus
one degree. He now knows what is expected and what is considered good enough.
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The Root Cause of the Problem
To get the process under control, you must first find the root cause of the problem. This can
be accomplished by running the gamut from simple methods such as pareto and matrix
analysis to complicated design experiments. A common problem is to attack the symptom
and not the problem. For example, if a breaker tripped at your house, you could reset the
breaker and hope for the best, replace the breaker box, or you could check for an overloaded
plug (too many appliances plugged into one outlet). In your manufacturing process, dont
make the mistake of rewiring the whole house before the actual problem is diagnosed.
Everyone has worked on a problem that magically went away, although you were not exactlysure why. It could be any one of the solutions you tried or a combination of any two. In this
case, you do not know if you have gotten to the root cause or not. You must be able to turn
the problem on and off to ultimately conclude that the problem has been solved. If you can
not turn the problem on and off it is likely that you have solved a symptom rather than a
problem. At this point you should ask why and continue to ask why until you find the
root cause.
Keeping Control of the Process
Once you have found the solution, keeping the process under control is an easier task.
Statistical Process Control (SPC) is a method of managing a process by gathering information
about it and using that information to adjust the process to prevent problems from occurring.
Using SPC is one way to keep your process under control. Poka-yoke, a Japanese word for
fail-safing, should also be applied. In the Pokayoke theory, parts andprocesses are designedso that doing the job right is easier than doing it wrong. An example of this is to design a part
that is asymmetrical so that it fits only one way, thus eliminating misinstallation. Machines
can be fitted with limit switches that will not allow it to cycle if all processes are not
completed in the correct order. These methods should not only be used by your company but
by your vendors as well.
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UNIFORM PlANT LOAD
The diversion between traditional manufacturing philosophy and JIT becomes apparent when
discussing the concept of Uniform Plant Load. Everyone will agree that we need to eliminate
waste and strive for quality to receive the most benefit from our manufacturing systems, but
there are two views on how to go about this. The traditional system calls for production at the
machine rate while JIT advocates production at the customer requirement rate. The JIT
concept of Uniform Plant Load states that balance between operations is more important than
speed, and ideally we should never produce faster than the customer requirement rate.
The concept of Uniform Plant Load incorporates two radically different facets of production.They are rate of production (cycle time) and frequency of production (level loading). It must
be remembered that neither of these concepts will achieve maximum results until the process
is under control and quality has been improved to world-class or near world-class standards.
Cycle Time
Traditional definitions of cycle time include the time it takes a machine to cycle through its
process or the time from start to completion of a product (throughput time). Under JIT, cycle
time is the total time required for a worker to complete one cycle of operations, including
walking, load/unload, inspect, etc. Cycle time should equal the customer requirement rate, or
better stated the sales rate. We should view the last step in the manufacturing process as when
the product gets sold, not when the product is completed. This rate is also expressed in terms
of takt time. Takt time is the total daily operating time divided by the total daily requirement.
Takt time tells you how many hours, minutes, or seconds are required for each part.
Takt is a German word for baton. In comparing a manufacturing process to an orchestra, the
rate at which the orchestra leader moves the baton is the rate at which the orchestra plays, just
as the rate of customer requirement is the rate of company production.
Companies that have produced as fast as possible (machine rate) for many years often
struggle with the concept of slowing down individual machines so as to achieve perfect
balance between operations. If your customer requirement rate is 20 parts per month, then
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why would you want to produce 30 parts per month? This would lead to the evils of
inventorythe consumption of space, waste in motion, and materials that hide problems.
Conceptually, each machine should run as if a rheostat were attached. The rheostat could be
dialed up or down as needed to produce at the exact rate required. If the requirement rate
changed from month to month then the production rate could be altered to meet these
requirements. If you set the last operation to the sales rate then each preceding operation
should feed the last operation at that rate. This system can then be exploded backwards
throughout the plant until the first operation (usually raw materials) is reached.
Workforce
If ten people are producing 20 parts per month in August, but only ten parts are needed in
September, five people should then be capable of producing the needed ten parts so that labor
costs remain constant. This reduction can only be accomplished with a good physical plant
layout (to be discussed later) and a well-trained, flexible workforce. The logical questions at
this point are: Where do the five people go?, and Where do they come from when
production goes back to 20? It must be made abundantly clear that the purpose of
implementing JIT is not to reduce the workforce. You can now use this idle time to cross-
train employees for even more flexibility. When not on the production line employees can
perform other tasks, attend team meetings, do preventative maintenance, make plans to
further improve the process and so forth. Rather than producing extra parts and dealing with
inventory, you are now optimizing employee time. That leads us to the golden rule of JIT:
Machines can be idle but people cannot.
We should not make the mistake of trying to find the perfect balance between parts produced
and manpower required. There is no perfect balance. We must decide how many parts the
line should produce that month, week, or day and balance to that number. Remember, the
answer is not to run the line as fast as possible, but to produce to the customer requirement
rate by deciding how fast the line must run to meet the particular deadline and how many
people are needed for this rate.
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SETUP TIME REDUCTION
Setup time is the interval between the production of one good part and the production of
another good but dissimilar part. Setup reduction is a prerequisite to implementing many
aspects of JIT by directly or indirectly influencing cycle time, level loading, work cells, pull
systems, cost, WIP, purchasing, floor space, quality, operator numbers, and batch sizes.
Everyone will agree that a two-hour setup reduced to two minutes is a great productivity
improvement, but this saved time should not be applied to longer production runs that
increase batch sizes. An hour saved that is transferred to the production of parts simply puts
those parts in inventory, which is the exact opposite of what we are striving for. Our
objective