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MECHANICAL ENGINEERING DEPARTMENT

DJJ5113

Politeknik Port Dickson http://www.polipd.edu.my

Published by Politeknik Port Dickson, Km. 14 Jalan Pantai, 71050 Si Rusa, Port Dickson, Negeri Sembilan Darul Khusus, Malaysia. Copyright © 2018 by Politeknik Port Dickson. All right reserved. No part of this mobile-note may be reproduced or transmitted in any form or by any means, electronic or mechanical, including photocopying, recording, or by any information storage and retrieval system, without written permission from the publisher.

DJJ6192 INDUSTRIAL MANAGEMENT

http://www.polipd.edu.my/

i

Preface

PREFACE

This mobile note is for students who are taking DJJ6192-Industrial Management course in the Mechanical Engineering Program, Polytechnic Malaysia, Ministry of Higher Education. The mobile note is published based on the curriculum for Course of Industrial Management issued by the Curriculum Division, Department of Polytechnic Education (DPE), Ministry of Higher Education of Malaysia.

Each chapter consists simple and concise explanation, more easier for beginner engineering student to understand and get some information. Hopefully student can get some benefit about the theory of Industrial Management and they can used as a basic knowledge when they involve in mechanical industries. The information in this book suitable with real situation in mechanical engineering field.

In study of mechanical engineering, student should learn how to construct and solve the problem by using fundamental theory and mathematical method. The content of this mobile note covers a whole range of topics learned by the students. With the completion of the accompanying examples and exercises that include the answers. The examples contain from simple and introductory to intermediates problems to help the students gain the confidence and understanding for each chapter. Last semester examinations questions also included in this mobile note. Hopefully students get the picture to solve the problem during final examination at the end of semester.

With the publication of this mobile note, students will be able to use it as one of their alternatives references. Furthermore, this mobile note is written based on the courses taken by the students. Therefore easier for students to adapt the information contained in this mobile note based on the teaching and learning process in the classroom.

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Acknowledgement

ACKNOWLEDGEMENT

In the name of Allah, all praise and thanks to Allah due to time and good health during preparing this mobile-note. Peace and blessing to Prophet Muhammad SAW.

Thanks to all those involved in the process of preparing this mobile-note. Hopefully the publication of this mobile-note will get benefit to all parties especially polytechnic student.

Team of Writers

Lead Editor : Sufandi Mohd Johan (PPD) Chapter 1 & 2 : Sufandi Mohd Johan (PPD) Chapter 3 & 4 : Abd Ghani Abd Malek (PPD)

General Introduction

xx

TABLE OF CONTENT

Preface i

Acknowledgement ii

List of Symbols v

List of Formula vi

Synopsis of Syllabus xiv

General Introduction xv

CHAPTER 1 : Management Concepts

Introduction 1

Industrial engineering and Management 2

Organization structures 19

Exercise 40

CHAPTER 2 : Plant Location, Layout and Line Balancing

Introduction 44

Plan location and layout 45

Facilities layout 45

Line balancing 46

Network analysis 47

Exercise 55

CHAPTER 3 : Inventory control management

Introduction 69

Inventory control and management concept 71

Inventory cost 71

Master scheduling material requirement 76

Just in Time 77

Exercise 112

CHAPTER 4 : scheduling management

Introduction 116


xx

Scheduling management 117

Scheduling in high volume system 117

Scheduling in low volume system 118

Exercise 155

References

SYNOPSIS OF SYLLABUS

INDUSTRIAL MANAGEMENT provides students to a strong fundamental understanding of industrial management prospect, production system planning such as inventory, scheduling, production system operation, facilities, plan location, layout and line balancing. This course also provides knowledge in quality control and human resource management.

PROGRAM LEARNING OUTCOMES (PLO)

Upon completion of the programme, graduates should be able to:

1. Apply knowledge of mathematics, science and engineering fundamentals to well-defined

mechanical engineering procedures and practices with specialisation in automotive.

2. analyse well-defined mechanical engineering specializing in automotive problems with respect to

operation and maintenance, including troubleshooting.

3. Conduct investigations and assist in the design of solutions for mechanical specializing in

automotive engineering systems.

4. Apply appropriate techniques, resources, and engineering tools to well defined mechanical

specializing in automotive engineering activities, with an awareness of the limitations.

5. Demonstrate an awareness and consideration for societal, health, safety, legal and cultural issues

and their consequent responsibilities.

6. Communicate effectively with the engineering community and society at large.

7. Function effectively as an individual and as a member in diverse technical teams.

8. Demonstrate an understanding of professional ethics, responsibilities and norms of engineering

practices.

9. Demonstrate an awareness of management, business practices and entrepreneurship.

10. Demonstrate an understanding of the impact of engineering practices, taking into account the

needs for sustainable development.

11. recognise the needs for professional development and to engage in independent and lifelong

learning


xx

LEARNING OUTCOMES

Upon completion of this course, students should be able to:-

No. Course Learning Outcome (CLO)

PLO

1.

Apply the basic concept of industrial management system in industry to solve related problems (C3).

PLO 1

2.

Analyze problems related to industrial management (C4). PLO 2

3.

Demonstrate good written communication skill in case study on assigned topics in groups (A3).

PLO 6

Learning Domain: LD1 Knowledge LD2 Practical Skills LD3 Communication Skills LD4 Critical Thinking and Problem Solving Skills LD5 Social Skills and Responsibilities LD6 Continuous Learning and Information Management Skills LD7 Management and Entrepreneurial Skills LD8 Professionalism, Ethics and Moral LD9 Leadership and Teamwork Skills

REFERENCES :

F Lawwrence Bennett, P.E. (1996), The management of engineering, John Wiley & sons. Inc, New Jersey, Canada. ISBN 0-471-59239-X Harold Kerzner.(2003). Project management a system approach to planning, scheduling and controlling (8thEd). John Wiley & sons. Inc., New Jersey, Canada. ISBN 0 -471-22577-0 O.P.Khanna. (2007). Industrial Engineering and management, Dhan pat Rai Publications, New Delhi, India. Patrick D.T.O, (1996).The Practice of Engineering Management a New Approach, British Library Cataloguing In Publication Data, England. ISBN 0471939749 William J. Stevenson. (2007), Operations management (8th ed.), McGraw-Hill International edition. Singapore.

DJJ6192

Industrial Management

SYLLABUS

1. Management Concepts

2. Plant Location, layout and line balancing

3. Inventory control management

4. Scheduling Management

5. Quality Management

6. Human Resource Management

ASSESSMENT

Lecturer hour assessment :

» Test ~ 2 (30%)

» Quiz ~ 2 (20%)

» End of Chapter ~ 2 (50%)

Final Examination : 1(100%) ~ 50%

COURSE LEARNING OUTCOMES

(CLO)

Apply the basic concept of industrial

management system in Industry.

Produce the suitable plant layout according to

product flow process and safety requirement.

Identify the suitable concept industrial

management system in related industry by

group.

CHAPTER 1

Management

Concept

CONCEPT OF INDUSTRIAL ENGINEERING

AND MANAGEMENT

Industrial engineering and management is a

highly organize modern methods carrying in

industry.

Its involve of a process such as planning,

organizing, directing, controlling and managing

the activities of any industry.

INDUSTRIAL ENGINEERING

What is industrial engineering?

Industrial engineering is a branch of engineering

which deals with the optimization of complex

processes or systems.

The prime objective of industrial engineering:

To increase the productivity

To eliminating waste and non-value added activities

To improve the effective utilization of resources

HISTORY AND DEVELOPMENT OF


Industrial engineering has developed during the

past 250 years

Pre industrial revolution (up to 1800)

Industrial revolution (1800-1890)

Scientific management (1890-1940)

Operation research and quantitative phase (1940-

1980)

Automation and computer integrated manufacturing

phase (1980-present)

HISTORY AND DEVELOPMENT OF


Industrial revolution

Begin in the mid eighteen century when factories

were first built and laborers were employed to work

with them.

Machine power began to substitute for human power.

Lead to mass production of economical goods.

Improved and less costly transportation system

became available.

Created larger market and larger organization

development.

Created formalized management practices.

CHARACTERISTIC AND TOOLS OF

MANAGEMENT SCIENCE

What is management science?

Management science (MS), is an interdisciplinary branch of applied mathematics devoted to optimal decision planning, with strong links with economics, business, engineering, and other sciences.

Characteristics and tools of scientific management:

Separation of planning and doing

Functional foremanship

Job analysis

Standardization

Scientific selection and training of workers

Financial incentives

Economy

Mental revolution

DIFFERENT SCHOOLS OF THOUGHT OR VARIOUS

APPROACH TO STUDY OF MANAGEMENT

PRINCIPLES OF MANAGEMENT BASED ON

HENRI FAYOL

Henry Fayol (1841-1925)

French industrialist and theorist

Began his working life as a young mining engineer at

the age of nineteen

Rising to managing at the age of 47 and only retiring

after his 77

His entrepreneurial successes won him considerable

fame and popularity

In 1916, he published “Administration Industrielle Et

Generale” that bought to light the distillation of a

lifetime’s experience of managerial work

PRINCIPLES OF MANAGEMENT BASED ON

HENRI FAYOL

ORGANIZATION STRUCTURES

What is organization?

Organization is the people who working together and

coordinating their actions to achieve specific goals

What is organization structure?

Organization structure is defined as the relatively

enduring allocation of work roles and administrative

mechanism that creates a pattern of interrelated

work activities and allows the organization to

conduct, co-ordinate and control its work activities

PRINCIPLES OF ORGANIZATION According to Urwick (Notes on the Theory of Organization, 1952), an

organization is built on ten principle:

TYPES OF AN ORGANIZATION AND ITS

FUNCTIONAL

Line, military or

scalar organization

It is the oldest and simple organization structure.

Manager exercise a direct authority over his subordinate.

Each department is self-contained and works independently of other departments.

Lines of authority are vertical (from top to bottom).


FUNCTIONAL

Line, military or scalar organization

Advantages Simple to establish and operate

Promotes prompt decision making

Easy to control as the director have direct control over their subordinates

Communication is fast and easy as there is only vertical flow of communication

Disadvantages Lack of specialization

Director might get overloaded with too many things to do

Failure of one manager to take proper decisions might affect the whole organization

Suitable for: Small businesses where there are few subordinates


FUNCTIONAL

Divided into a number of functional areas. This organization has grouping of activities in accordance with the function of an organization such as production, marketing, finance, human resource and so on.

The specialist in charge of a functional department has the authority over all other employees for his function.

Functional

organization


FUNCTIONAL

Functional organization

Advantages Logical and reflection of functions

Follows principle of occupation specialization

Simplifies training

Better control as the manager in charge of each functional department is usually a specialist

Disadvantages Over specialization and narrow viewpoints of key personnel can limit the

organization growth

Reduced coordination between function

Conflicts between different function could be detrimental for the organization as a whole

Difficult for general managers to coordinate different departments

Suitable for: Larger organization where there is scope for specialization. Once proper

coordination among different function is achieved, it could lead to sure success for an organization


FUNCTIONAL

Line and staff

organization

A combination of line

and functional

structures. The

authority flows in

vertical line and get

the help of staff

specialist who are in

advisory. When the

line executive need

advice, these staff

specialists are

consulted.


FUNCTIONAL

Line and staff organization

Advantages

Line managers are provided by expert advice by these specialists. Staff managers provide specialist advice which can improve quality of decisions in various department

Disadvantages

Line managers and staff managers might have conflict on particular issues. Co-ordination may be a problem.

Suitable for:

Line and staff organization is very suitable for large organization


FUNCTIONAL

Project organization

The project structure consist of a number of horizontal organizational units to complete projects of a long duration. A team of specialist from different areas is created for each project. Usually, this team is managed by the project manager. The project staff is separate from and independent of the functional departments.


FUNCTIONAL

Project organization

Advantages

Special attention can be provided to meet the complex demand of the project

It allows maximum use of specialist knowledge thus chances of failure are very less

Project staff works as a team towards common goal which result in high motivation level for its members

Disadvantages

As the project staff consist of personnel from diverse fields, it might be quite challenging for the project manager to coordinate among them


FUNCTIONAL

Matrix organization

Combination of two structures, functional and project structure.

Functional department is a permanent feature of the matrix structure and retains authority for overall operation of the functional units

Project teams are created whenever specific projects require a high degree of technical skill and other resources for a temporary period

Project team forms the horizontal chain and functional department create a vertical chain of command


FUNCTIONAL

Matrix organization

Advantages

Professional identification is maintained

Pinpoints product-profit responsibility

Disadvantages

Conflict in organization authority exists

Requires manager effective in human relations

Suitable for:

Industries with highly complex product system such as weapons


FUNCTIONAL

Reality is………………

DIFFERENTIATE BETWEEN POLICIES, GOAL

AND OBJECTIVES

Policy

Is a guiding principle used to set direction in an

organization. It can be a course of action to guide and

influence decisions.

Goals

Goals denote what an organization hopes to

accomplish in a future period of time

Objectives

Objectives are the ends that state specifically how the

goals shall be achieved.

MANAGEMENT PROCESS

EXERCISES

1. Define the term “industrial management”.

2. Briefly explain the scope of industrial management.

3. Give the concept of industrial management.

4. Write short notes of “Evolution of industrial management”.

5. State the definition of organizational structure.

6. Identify the three major functional areas of business organizations and briefly describe how they interrelate.

7. Define organization structure and list down the advantages and disadvantages of an organization.

8. Give the applications of industrial management.

9. From your opinion, in what ways can industrial management engineering’s make process better?

10. Why are building information systems important in industrial management?

THE END Thank You

CHAPTER 2

Plant Location, Layout

and Line Balancing

1

PLAN LOCATION AND LAYOUT

What is plant location?

The establishment of an industry at a particular

place

What is plant layout?

Plant layout is defined as the most effective physical

arrangement of machines, processing equipment and

service department to have the best co-ordination

and efficiency of man, machine and material in a

plant.

2

CONCEPT AND OBJECTIVE OF GOVERNING

PLANT LOCATION

Concept governing plant location

The selection of location is a key decision as large

investment is made in building plant machinery

Before a location is selected, long range forecast

should be made anticipating future needs of the

company

Objective of selecting location

Minimize the cost of production and maximize

revenue

3

FACTORS GOVERNING PLANT LOCATION

Factors governing plant location

1. Country decision

Political risk, government rules, attitudes and

incentives

Cultural and economic issues

Location of market

Labor talent, attitudes, productivity and cost

Availability of supplies, communication and energy

Exchange rates and currency risk

4


2. Region/community decision

Corporate desire

Attractiveness of region

Labor availability and cost

Cost and availability of utilities

Environmental regulation of state and town

Government incentive and fiscal policies

Land/construction cost

Customer

5


3. Site decision

Site, size and cost

Air, rail, highway and waterway system

Zoning restrictions

Proximity of services/supplies needed

Environmental impact issues

6

OBJECTIVE OF PLANT LAYOUT

Layout is one of the key decisions that determine

the long run efficiently of operations

The objective of layout is:

To develop an effective and efficient layout that will

meet the firm’s competitive requirement

7

PRINCIPLE OF PLANT LAYOUT

The principle of plant layout can be stated as:

1. Integration of all factors The plant should integrate all the essential resources of

man, machines and materials in order to give an optimum level of production.

2. Minimum movement The less the movement of man, machines and materials,

the less will be the cost of production. Thus, minimum movement of these resources will provide cost efficiency.

3. Unidirectional flow All materials should progressively move towards the same

direction (towards the stage of completion). Any back-tracking should be avoided here.

8


4. Efficient space handling The space used up during the plant work also cost money

as the more space required, the more will be the floor rent. The materials should be organized in stack in a proper and recognizable order to maintain the space efficiency.

5. Inherent safety The environment of the plant should be safe for the

workers as well as the machines. There should be fire extinguishers and fire exit placed strategically. There should be minimum contact of the labor to toxic chemicals and environments.

6. Maximum observation capacity The layout of the plant should such that all of its resources

and workforce can be observed and evaluated at all points in time. This helps in better supervision of work and helps in increasing both effectiveness and safety.

9


7. Maximum accessibility The layout of the plant should ensure that all essential resources are

accessible to the labor and machines without any delay. The aisles should be free from obstacle. The material should be placed as close to the machines concerned as possible.

8. Minimum handling The ineffective handling of materials leads to a raise in cost. Materials

should be handled in stacks and transferred in one go. Handling of a material twice in the same direction must be avoided.

9. Maximum protection The layout should ensure the protection of the materials and

machines while they are in the working or the storage stage. The security system should be efficient without making too many doors or barriers.

10. Maximum flexibility The plant layout should not be rigid and permanent. If the need

arises, the plant layout should be able to change itself without being expensive.

10

PLANT LAYOUT PROCEDURE

1. Analyze the product to be produced

2. Determine the process required to manufacture

the product

3. Prepare layout planning chart

4. Determine work station

5. Analyze storage area requirements

6. Establish minimum aisle widths

7. Establish office requirements

8. Consider personnel facilities and services

9. Survey plant services

10. Provide for future expansion 11

FACILITIES LAYOUT

Facilities layout is the process of determining the

placement of department, workgroups,

workstation, machines and stock holding points

within a facility are determined.

12

REASON FOR FACILITIES LAYOUT

1. Productivity improvement through elimination

or reduction of unnecessary activities.

2. Improved health and safety.

3. To converse and reduce consumption of energy

4. Lower the risk of fire, lower maintenance cost,

etc.

13

FACILITIES PLANNING OBJECTIVE

1. Minimize material handling cost

2. Minimize overall production time

3. Effectively utilize existing space

4. Provide for employee convenience

5. Assure workplace safety and comfort

6. Facilitate the manufacturing process

7. Facilitate the organizational structure

14

TYPES OF LAYOUT

The layouts are differentiated by the types of

workflow they entail, and workflow in turn is

dictated by the nature of product.

Basic types of layouts:

Process layout

Product layout

Fixed position layout

15

TYPES OF LAYOUT

16

A process layout (also known as functional layout) is a type of facility layout in which the floor plan is arranged with similar processes or machines located together.

Variable workflow occurs when variety of variation of a single product are produced.

In this layout, similar equipment are group and located at one place.

Process Layout

TYPES OF LAYOUT

Process layout

Advantages

Greater flexibility

Better and more efficient supervision possible through specialization

Breakdowns can be taken care by shifting the job to another machine

Capability of different product line can be expanded easily

Disadvantages

More work in progress

More floor space

More distances travelled by the product 17

TYPES OF LAYOUT

18

A product layout refers to a production system where the work stations and equipment are located along the line of production.

It is appropriate for producing one standardized product, usually in large volume.

The machine are arrange according to the progressive steps by which the product is made.

Product Layout

TYPES OF LAYOUT

Product Layout

Advantages

Material handling cost can be reduced

Requires less floor area

Facilitates better production control

Production bottlenecks are avoided

Disadvantages

Expansion of production line is difficult

There is difficult in supervising

Breakdown of equipment disrupts the production 19

TYPES OF LAYOUT

Process vs. Product Layouts

20

TYPES OF LAYOUT

21

A production technique used to assemble products that are too large, bulky, or fragile to safely or effectively move to a location for completion.

Used when product is large

Product is difficult or impossible to move

All resources must be brought to the site

Fixed position layout

PLANT LAYOUT PROCESSES SELECTION

Three Primary Question Bear on Plant Layout

Process Selection

How much variety in products or services will the

system need to handle?

What degree of equipment flexibility will be needed?

What is the expected volume of output?

Answer to those expected question will serve as a

guide to selecting an appropriate process

22

PLANT LAYOUT PROCESSES SELECTION

Basic Plant Layout Process Types

There are five basic process types

Job shop

Batch

Repetitive

Continuous

Project

23

Job Shop Batch Repetitive Continuous

Description Customized

goods or

services.

Semi-

standardize

d goods or

services.

Standardized

goods or

services.

Highly

standardized

goods or

services.

Advantages Able to

handle a

wide variety

of work.

Flexibility. Low unit

cost, high

volume,

efficient.

Very

efficient,

very high

volume.

Disadvantages Slow, high

cost per

unit,

complex

planning

and

scheduling.

Moderate

cost per

unit,

moderate

scheduling

and

planning.

Low

flexibility,

high cost of

downtime.

Very rigid,

lack of

variety,

costly to

change, very

high cost of

downtime.

FIVE BASIC PROCESS TYPES

24

Activity/

function

Job

shop

Batch Repetitive/

assembly

Continu

ous

Project

Cost

estimation

Difficult Somewhat

routine

Routine Routine Simple to

complex

Cost per

unit

High Moderate Low Low Very high

Equipment

used

General

purpose

General

purpose

Special

purpose

Special

purpose

Varied

Fixed cost Low Moderate High Very

high

Varied

Variable

cost

High Moderate Low Very low High

Labor

skills

High Moderate Low Low to

high

Low to

high

FIVE BASIC PROCESS TYPES (CONT.)

25

Activity/

function

Job shop Batch Repetitiv

e/

assembly

Continuo

us

Project

Marketin

g

Promote

capabiliti

es

Promote

capabiliti

es, semi-

standardi

zed goods

and

services

Promote

standardiz

ed goods

and

services

Promote

standardiz

ed goods

and

services

Promote

capabili

ties

Scheduli

ng

Complex Moderate

complex

Routine Routine Comple

x

subject

to

change

Work in

process

inventory

High High Low Low Varied

FIVE BASIC PROCESS TYPES (CONT.)

26

LINE BALANCING AND NETWORK ANALYSIS

Line balancing is the process assigning task to

workstation in such a way that the workstation

have approximately equal time requirements

Line balancing is usually undertaken to

minimize imbalance between machines or

personnel while meeting a required output from

the line

Cycle time is the maximum time allowed at each

workstation to complete its set of task on a unit

Precedence diagram is a diagram that shows

elemental tasks and their precedence

requirements 27


Efficiency = 𝑡𝑎𝑠𝑘 𝑡𝑖𝑚𝑒

𝑛𝑢𝑚𝑏𝑒𝑟 𝑜𝑓 𝑤𝑜𝑟𝑘 𝑠𝑡𝑎𝑡𝑖𝑜𝑛 𝑥 (𝑎𝑠𝑠𝑖𝑔𝑛𝑒𝑑 𝑐𝑦𝑐𝑙𝑒 𝑡𝑖𝑚𝑒𝑠)

28


The table below shows line of work with time

needed to produce product R. Given daily

production rate is 480 productive minutes of

work available per day. Furthermore, the

production schedule requires that 40 units be

completed as output from the assembly line each

day. Find :

29


30

1. Construct The

Precedence Chart

2. Calculate Cycle Time

3. Calculate Minimum

Number of Work

Station

4. Calculate The

Efficiency

EXAMPLES:-

31

Assembly Line Balancing

Line-balancing activities are usually undertaken to meet a certain

required output from the line. In order to produce at a specified rate,

management must know the tools, equipment, and works methods

used. Then the time requirements for each assembly task (such as

drilling a hole, tightening a nut, or spray-painting a part) must be

determined. Management also need to know the precedence

relationship among the activities that is the sequence in which

various tasks need to be performed. Let us construct a precedence

chart for the tasks data in Example 1

We want to develop a precedence diagram for an electrostatic

copier that requires a total assembly time of 66 minutes. Table

and figure give the tasks, assembly times, and sequence

requirements for the copier.

EXAMPLE 1

EXAMPLE 1

32

33

Once we have constructed a precedence chart summarizing

the sequences and performance times, we turn to the job of

grouping tasks into job stations to meet the specified

production rate. This process involves three steps:

1. Take the demand (or production rate) per day and divide it

into the productive time available per day (in minutes or

seconds). This operation gives

34

A six-station solution to the Line-Balancing Problem

Time of 12 minutes as possible. The first work station consumes 10 minutes

and has an idle time of 2 minutes.

The second workstation uses 11 minutes, and the third consumes the full 12

minutes. The fourth workstation group three small tasks and balances

perfectly at 12 minutes . The fifth has 3 minute of idle time, the sixth

(consisting of tasks G and 1) has 2 minutes of idle time per cycle. Total idle

time for this solution is 6 minutes per cycle.

We can compute the efficiency of line balance by dividing the total tasks time

by the product of the number of workstations times the assigned cycle time:

Efficiency = 𝑡𝑎𝑠𝑘 𝑡𝑖𝑚𝑒

(𝑛𝑢𝑚𝑏𝑒𝑟 𝑜𝑓 𝑤𝑜𝑟𝑘𝑠𝑡𝑎𝑡𝑖𝑜𝑛𝑠)×(𝑎𝑠𝑠𝑖𝑔𝑛𝑒𝑑 𝑐𝑦𝑐𝑙𝑒 𝑡𝑖𝑚𝑒)

Management often compares different levels of efficiency for various numbers

of workstations. In this way, the firm can determine the sensitivity of the line

to changes in the production rate and workstation assignments.

35

Management often compares different levels of efficiency for various numbers of workstations. In this way, the firm can determine the sensitivity of the line to changes in the production rate and workstation assignments.

We can calculate the balance efficiency for Example 2 as follow:

Efficiency =66 𝑚𝑖𝑛𝑢𝑡𝑒𝑠

6 𝑠𝑡𝑎𝑡𝑖𝑜𝑛𝑠 ×(12 𝑚𝑖𝑛𝑢𝑡𝑒𝑠 =66

72 = 91.7%

Opening a seventh workstation, for whatever reason, would decrease the efficiency of the balance to 78.6%:

Efficiency = 66 𝑚𝑖𝑛𝑢𝑡𝑒𝑠

7 𝑠𝑡𝑎𝑡𝑖𝑜𝑛𝑠 ×(12 𝑚𝑖𝑛𝑢𝑡𝑒𝑠 = 78.6%

Large-scale line balancing problems, like large process layout problems, are often solved by computers. Several different computer programs are available to handle the assignment of workstations an assembly lines with 100 (or more) individual work activities. Both the computer routine called COMSOAL

EXAMPLE 2

36

An assembly line, whose activities are shown below, has an eight-

minute cycle time. Draw the precedence graph and find the minimum

possible number of workstations. Then arrange the work activities into

workstations so as to balance the line. What is the efficiency of this line

balance?

SOLUTION

37

The theoretical minimum number of workstations is:

𝑡

𝐶𝑦𝑐𝑙𝑒 𝑡𝑖𝑚𝑒 =

28 𝑚𝑖𝑛𝑢𝑡𝑒𝑠

8 𝑚𝑖𝑛𝑢𝑡𝑒𝑠 = 3.5 or 4 stations

The precedence graph and one good layout are shown in Figure 9.27.

Efficiency = 𝑇𝑜𝑡𝑎𝑙 𝑡𝑎𝑠𝑘 𝑡𝑖𝑚𝑒

𝑁𝑢𝑚𝑏𝑒𝑟 𝑜𝑓 𝑤𝑜𝑟𝑘𝑠𝑡𝑎𝑡𝑖𝑜𝑛𝑠 ×(𝑐𝑦𝑐𝑙𝑒 𝑡𝑖𝑚𝑒) =

28

(4)(8) = 87.5%

EXERCISE

38

1. State and describe the factor governing plant location.

2. Why are plant location decisions important for detailed analysis?

3. The table below shoes line of work with time needed to produce product

R. given daily production rate is 540 minutes and daily production

quality are 60 units.

Work Time (minutes) Work before

A 3 -

B 6 A

C 7 A

D 5 A

E 2 A

F 4 B,C

G 5 C

H 5 D,E,F,G

i. Draw the production line balancing.

ii. Calculate the production cycle time.

iii. Calculate the minimum number of workstation for the production.

iv. Determine the group of workstation.

v. Prove that there is lees efficiency if there are too many workstations.

vi. Calculate idle time.

THE END Thank You 39

CHAPTER 3

INVENTORY CONTROL

MANAGEMENT

1

INVENTORY CONTROL AND MANAGEMENT

CONCEPT

What is inventory?

Inventory is an idle stock of physical goods that

contain economic value, and are held in various forms

by an organization in its custody awaiting packing,

processing, transformation, use or sale in a future

point of time.

Inventory management is a very important

function that determines the health of the supply

chain as well as the impacts the financial health

of the balance sheet.

2


CONCEPT

From the above definition the following points

stand out with reference to inventory:

3


CONCEPT

List objective of inventory control and management:

To ensure adequate supply of products to customer and

avoid shortages as far as possible

To make sure that the financial investment in inventories

is minimum

Efficient purchasing, storing, consumption and accounting

for materials.

To maintain timely record of inventories of all the items

and to maintain the stock within the desired limits

To ensure timely action for replenishment

To provide a reserve stock for variations in lead time of

delivery of materials

To provide a scientific base for both short–term and long-

term planning of materials 4


CONCEPT

Benefits of inventory control

It is establish fact that through the practice of

scientific inventory control, the stocks can be reduced

anywhere between 10% to 40%. The benefits of

inventory control are:

Improvement in customer relationship because of the timely

delivery of goods and services

Smooth and uninterrupted production

Efficient utilization of working capital

Helps in minimizing loss due to deterioration, obsolescence

damage and preliferage

Economy in purchasing

Eliminates the possibility of duplicate ordering 5


CONCEPT

Types of inventory

1. Raw Materials Raw materials are those basic un-fabricated materials

which have not undergone any operation since they are received from the suppliers. (e.g. : Round bars, angles, channels, pipe, etc.)

2. Bought Out Parts These parts refer to those finished parts, subassemblies

which are purchased from outside as per the company’s specification.

3. Work-In-Process (WIP) These refer to the items or materials in partially completed

condition of manufacturing. (e.g. : Semi-finished product at the various stages of manufacture.)

6


CONCEPT

Types of inventory (Continued)

4. Finished Goods Inventories These refer to the completed products ready for dispatch.

5. Maintenance, Repair and Operating Stores Normally these inventories refer to those items which do

not form the part of the final product but are consumed in the production process. (e.g. : Machine spare, oil, grease.)

6. Tools Inventory Includes both standard tools and special tools.

7. Miscellaneous Inventories Office stationaries and other consumable stores. 7

INVENTORY COST

There are three basic costs associated with inventory, holding cost (also known as carrying cost), ordering cost and setup cost.

1. Holding cost Holding cost are the cost of holding items in storage. These

vary with the level of inventory and occasionally with the length of time an item is held, that is, the greater the level of inventory over time, the higher the holding cost.

Holding cost can include the cost of losing the use of funds tied up in inventory. Direct storage cost such as rent, heating, cooling, lighting, security, refrigeration, record keeping and logistics, interest on loans used to purchase inventory, depreciation, obsolescence as market for products in inventory diminish, product deterioration and spoilage, breakage, taxes and pilferage. 8

INVENTORY COST

2. Ordering cost

Ordering cost are the cost associated with

replenishing the stock of inventory being held. These

are normally expressed as a dollar amount per order

and are independent of the order size. Thus, ordering

cost vary with the number of orders made (as the

number of orders increases, the ordering cost

increases)

Cost incurred each time an order is made can include

requisition cost, purchase orders, transportation and

shipping, receiving, inspection, handling and placing

in storage, accounting and auditing. 9

INVENTORY COST

3. Setup Cost

Cost to prepare a machine or process for

manufacturing an order.

10

INVENTORY MODELS FOR INDEPENDENT

DEMAND

Independent demand items are finished product

that are not a function of, or dependent upon,

internal production activity.

Independent demand is usually external and

thus beyond the direct control of the

organization.

11

ECONOMIC ORDER QUANTITY MODEL

(EOQ)

The most widely used and traditional means for

determining how much to order in a continuous

system is known as the Economic Order Quantity

(EOQ) model.

The function of the EOQ model is to determine

the optimal order size that minimizes total

inventory cost

12


(EOQ)

1. Demand is known, constant, and independent

2. Lead time is known and constant

3. Receipt of inventory is instantaneous and complete

4. Quantity discounts are not possible

5. Only variable costs are setup and holding

6. Stock-outs can be completely avoided

Important Assumptions

13


(EOQ)

o The Inventory Order Cycle

14


(EOQ)

The EOQ Cost Model

15


(EOQ)

Annual Setup Cost (Ordering Cost)

16


(EOQ)

Annual Holding Cost (Carrying Cost)

17


(EOQ)

Optimum Order Quantity

Optimal order quantity is found when annual

setup cost equals annual holding cost

Solving for 𝑄𝑜𝑝𝑡 =

18


(EOQ)

Reorder Points

EOQ answers the “how much” question.

The reorder point (ROP) tells “when” to order.

19


(EOQ)

Reorder Points

How to find d?

20


(EOQ)

Formula That You Must Know in (EOQ)

Optimal Quantity, 𝑄𝑜𝑝𝑡 = 2𝐷𝑆

𝐻

Total Annual Inventory Cost, = 𝑄∗

2𝐻 +

𝐷

𝑄∗ S

Average Annual Inventory Cost (Minimum), = 2 𝑥 𝐷 𝑥 𝑆 𝑥 𝐻

Length of Order Cycle, = 𝑄∗

𝐷

Optimum Number of Order, = 𝐷

𝑄∗

Reorder Points, (ROP) = d x L

21


(EOQ)

Example 1

SaveMart needs 1000 coffee makers per year. The cost of each coffee maker is RM78. Ordering cost is RM100 per order. Carrying cost is RM20 of per unit cost. Lead time is 5 days. SaveMart is open 360 days/year. Calculate:

i. The EOQ Model

ii. How many times per year does the store reorder?

iii. What is the length of order cycle?

iv. What is the total annual cost if the EOQ quantity is ordered?

v. What is the reorder point quantity? 22


(EOQ)

Example 2

A manufacturer has to supply his customer 3600

units of his product per year. Shortages are not

permitted. Inventory carrying cost amounts

RM1.20 per unit. The set-up cost per run is

RM80. Find:

i. Economic order quantity

ii. Optimum number of orders per unit

iii. Average annual inventory cost (minimum)

23

PRODUCTION ORDER QUANTITY MODEL

(EPQ)

Used when inventory builds up over a period of

time after an order is placed.

Used when units are produced and sold

simultaneously.

24


(EPQ)

25


(EPQ)

26


(EPQ)

27


(EPQ)

28


(EPQ)

Formula That You Must Know in (EPQ)

Optimum Quantity for EPQ, Q* = 2𝐷𝑆

𝐻 [ 1 − 𝑑

𝑝 ]

Maximum Inventory Level , = pt – dt

Total minimum Annual Inventory Cost, = S 𝐷

𝑄∗ + H

𝑄∗

2 ( 1 -

𝑑

𝑝 )

Production Run Length, = 𝑄∗

𝑃

Cycle Time, = 𝑄∗

𝑑

Optimum Number of Order, = 𝐷

𝑄∗

Maximum Inventory Level, = Q ( 1 – 𝑑

𝑝 )

29


(EPQ)

Example

30


(EPQ)

31


(EPQ)

Example 3

I-75 Carpet Store has its own manufacturing facility in which it produces Super Slag carpet. The ordering cost is RM150 for setting up the production process. Carrying cost is RM0.75 per yard and the annual demand is 10000 yards. The manufacturing facilities operates for 311 days in a year and produces 150 yards of carpet per day. Compute:

i. The optimal order size

ii. Total inventory cost

iii. The length of time to receive an order

iv. The number of orders per year and,

v. The maximum inventory level 32

QUANTITY DISCOUNT MODEL

Reduced prices are often available when larger

quantities are purchased

Trade-off is between reduced product cost and

increased holding cost

Total cost = Setup cost + Holding cost + Product

cost ( Demand x Actual Cost )

33


Steps in analyzing a quantity discount

1. For each discount, calculate Q*.

2. If Q* for a discount doesn’t qualify, choose the

smallest possible order size to get the discount.

3. Compute the total cost for each Q* or adjusted

value from Step 2.

4. Select the Q* that gives the lowest total cost.

34


A typical quantity discount schedule

35


Calculate Q* for every discount.

Q* = 2𝐷𝑆

𝐼𝑃

36


37


38


39


Example 4

The maintenance department of a large hospital

uses about 180 cases of liquid cleanser annually.

Ordering cost are RM25, carrying cost are RM5

per case a year, and the new schedule indicates

that orders of less than 45 cases will cost RM2

per case, 45 to 69 will cost RM1.70 per case, and

more than 70 cases will cost RM1.40 per case.

Determine the optimal order quantity and total

cost. 40

MASTER PRODUCTION

SCHEDULING (MPS)

Is a detailed plan that states how many end

items will be produced within specified periods of

time.

End items can be either finished products or the

highest level assemblies from which shippable

products are built.

MASTER PRODUCTION SCHEDULING

(MPS) (CONT.)

It specifies what is to be made and when.

Must be accordance with the production plan.

The production plan sets the overall level of

output in a broad terms.

As the process moves from planning to execution

each step must be tested for feasibility.

MASTER PRODUCTION

SCHEDULING (MPS) (CONT.)

Specifies what is to be made and when.

Must be in accordance with the aggregate

production plan.

Aggregate production plan sets the overall level

of output in broad terms.

As the process moves from planning to execution

each step must be tested for feasibility.

MASTER PRODUCTION

SCHEDULING (MPS) (CONT.)

Can be expressed in any of the following terms:

A customer order in a job shop (make-to-order)

company.

Modules in a repetitive (assemble-to-order or

forecast) company.

An end item in a continuous (stock-to-forecast)

company.

MASTER PRODUCTION SCHEDULING (MPS) (CONT.)

Gross Requirements for Crabmeat Quiche

Gross Requirements for Spinach Quiche

Day 6 7 8 9 10 11 12 13 14 and so on

Amount 50 100 47 60 110 75

Day 7 8 9 10 11 12 13 14 15 16 and so on

Amount 100 200 150 60 75 100

For Nancy’s Specialty Foods

Example:

MATERIAL REQUIREMENT PLANNING

(MRP)

Define fundamental of MRP

MRP is a technique for determining the quantity and

timing for the acquisition of dependent demand items

needed to satisfy master production schedule

requirements.

46


(MRP)

MRP refers to the basic calculations used to determine component requirement from end item requirements.

A technique of working backward from the schedule to determine the requirements for component needed to meet the master production schedule.

It determine what component are needed, how many are needed, when they are needed and when they should be ordered so that they are likely to be available as needed. 47

BENEFITS AND REQUIREMENT OF MRP

Inventory reduction MRP determine what component are needed, how many

are needed, when they are required in order to meet the master schedule.

Reduction in the manufacturing and delivery lead times MRP identifies materials and component quantities,

timings when they are needed, availabilities and procurements and actions required to meet delivery deadlines.

Realistic delivery commitments By using MRP, production can give marketing timely

information about likely delivery times to prospective customers.

48

BENEFITS AND REQUIREMENT OF MRP

Increased efficiency

MRP provides a close coordination among various

work centers and hence increases the efficiency of

production system.

Order planning and control

Can determine when to release orders and for what

quantities of materials/component.

Priority planning and control

Could easily compare the expected date of availability

and the need date for each component. 49

MRP SYSTEM

Inputs to MRP MPS, Inventory Status File and BOM

Output to MRP Order release requirements, orders rescheduling and planned

orders

50

EXAMPLE OF MRP LOGIC AND PRODUCT

STRUCTURE TREE

51


STRUCTURE TREE

52


STRUCTURE TREE

53


STRUCTURE TREE

54


(MRP) EXAMPLE

55


(MRP) EXAMPLE

56


(MRP) EXAMPLE

57


(MRP) EXAMPLE

58


(MRP) EXAMPLE

59


(MRP) EXAMPLE

60

EXAMPLE

A toy manufacture uses 48k rubber wheel per year

for a popular dump truck . The firm make its own

wheel , which it can produce at rate of 800 per day.

The toy truck are assemble uniformly over entire

year . Carrying cost is $1 per wheel a year . The

firm operate 240 days per year . Determine the –

i. Optimal run size

ii. Minimum total amount cost for carrying and

setup

iii. Cycle time for optimum run size

iv. Run time

61

ANSWER

Given:-

D = 48,000 wheels per year

S = $45

H = $1 per wheel per year

p = 800 wheels per day

d = 48,000 wheels per 240 days or 200 wheels per day

62

EXERCISE 1

A local distributor for a national tires company

expects to sells approximately 9600 steel belted

radial tires of certain size and treated design next

year. Annual carrying cost is $16 per tires and

ordering cost is $75. The distributor operates 288

days a year.

i. What is EOQ model?

ii. How many times per year does the store

reorder?

iii. What is the length of order cycle?

iv. What is the annual cost if the EOQ quantity is

ordered?

63

EXERCISE 2

A large bakery buys flours in 25-pound bags. The bakery uses an average of 4,860 bags a year. Preparing and order and receiving a shipment of flour involves a cost of $10 per order. Annual carrying costs are $75 per bag.

i. Determine the economic order quantity

ii. What is the average number of bag on hand?

iii. How many orders per year will there be?

iv. Compute the total cost of ordering and carrying flour

v. If ordering costs were to increase by $1 per order, how much that would affect the minimum total annual cost?

64

EXERCISE 3

A large law firm uses an average of 40 boxes of copier paper a day. The firm operates 260 days a year. Storage and handling costs for the paper are $30 a year per box, and its costs approximate $60 to order and receive a shipment of paper.

i. What order size would minimize the sum of annual ordering and carrying cost?

ii. Compute the total annual cost using your order size from part a?

iii. Except for rounding, are annual ordering and carrying cost always equal at EOQ?

iv. The office manager is currently using an order size of 200 boxes. The partners of the firm expect the office to be managed “in a cost-efficient manner.” Would you recommend that the office manages use the optimal order size instead of 200 boxes? Justify your answer.

65

CHAPTER 4

SCHEDULING MANAGEMENT 1

SCHEDULING MANAGEMENT

What is Scheduling Management?

Scheduling Management is to establish the timing of

the use of equipment, facilities, and human activities

in an organization.

Benefit of Scheduling Management

Minimize the completion time

Maximize utilization

Minimize work in process

Minimize customer waiting time

2

SCHEDULING CONCEPTS

A character of scheduling is the productivity, the relation between quantity of inputs and quantity of output. The concepts here are:

Inputs Inputs are plant, labor, materials, tooling, energy and a clean environment.

Outputs Outputs are the products produced in factories either for other factories or for the end

buyer. The extent to which any one product is produced within any one factory is governed by transaction cost.

Output within the factory The output of any one work area within the factory is an input to the next work area

in that factory according to the manufacturing process. For example the output of cutting is an input to the bending room.

Output for the next factory By way of example, the output of a paper mill is an input to a print factory. The output

of a petrochemicals plant is an input to an asphalt plant, a cosmetics factory and a plastics factory.

Output for the end buyer Factory output goes to the consumer via a service business such as a retailer or an

asphalt paving company.

Resource allocation Resource allocation is assigning inputs to produce output. The aim is to maximize

output with given inputs or to minimize quantity of inputs to produce required output. 3

FACTORS AFFECTING SCHEDULING

There are multiple factors affecting the

scheduling and they are broadly classified into

two which is:

External Factors

Internal Factors

4


External Factors

Basically concerned with:

Customer’s demand

Customer’s committed delivery dates

The Dealers and retailers inventories

Internal Factors

Basically concerned with:

Stock of finished goods kept by company.

Processing time of each product.

Type of machines available.

Availability of personnel.

Availability of materials.

Manufacturing facilities available in the company.

Economic production runs (EPR) or optimum lot size. 5


6

BENEFITS OF SCHEDULING

The following are the benefits of scheduling:

Minimize completion time

Maximize utilization

Minimize work in process

Minimize customer waiting time

7

SCHEDULING IN HIGH-VOLUME SYSTEM

Concept scheduling in high-volume system

High-volume systems are characterized by standardized equipments and activities that provide identical or highly similar operations on customers or products as they pass through the system.

All items follow virtually the same sequence of operations.

The goal is to get a high utilization of labor and equipment. Because of the highly repetitive nature of these systems,

many of the loading and sequence decisions are determined during the design of the system.

8

FACTORS SUCCESS IN SCHEDULING IN

HIGH-VOLUME SYSTEM.

1. Process and product design.

Cost and manufacturability are important, as is

achieving a smooth flow through the system.

2. Preventive maintenance.

Keeping equipment in good operating order can

minimize breakdowns that would disrupt the flow of

work.

3. Rapid repair when breakdowns occur.

This can require specialists as well as stocks of

critical spare parts. 9

FACTORS SUCCESS IN SCHEDULING IN

HIGH-VOLUME SYSTEM.

4. Optimal product mixes.

Techniques such as linear programming can be used to determine optimal blends of inputs to achieve desired outputs at minimal costs.

5. Minimization of quality problems.

Quality problems can be extremely disruptive. Moreover, when output fails to meet quality standards, not only is there the loss of output but also a waste of the labor, material, time, and other resources that went into it.

6. Reliability and timing of supplies.

Shortage of supplies is an obvious source of disruption and must be avoided. On the other hand, is the solution is to stockpile supplies, that can lead to high carrying costs.

10

SCHEDULING IN LOW-VOLUME SYSTEM

Concept scheduling in low-volume system

In low-volume systems, products are made to order,

and orders usually differ considerably in terms of

processing requirements, materials needed,

processing time, and processing sequence and setups.

Because of these circumstances, job-shop scheduling

is usually fairly complex.

This is compounded by the impossibility of

establishing firm schedules priori to receiving the

actual job orders. 11

TYPES OF LOW-VOLUME SCHEDULING

There are two basic types in low-Volume scheduling

which is:

Loading

Sequencing

Loading

Refers to the assignment of jobs to processing (work)

centers and to various machines in the work centers.

When two or more jobs are to be processed and there are a

number of work centers capable of performing the required

work.

Managers often seek an arrangement that will minimize

processing and setup costs, minimize idle time among work

centers, or minimize job completion time.

12


Loading There are a few more fractions in loading which are:

Gantt Chart To organize and clarify the actual or intended use of

resources in a time framework.

Input/Output Control To manage work flow so that queues and waiting times are

kept under control.

Assignment Method Is a special class of linear programming models that assign

tasks or jobs to resources. Only one job (or worker) is assigned to one machine (or project). Objective is to minimize cost or time.

13


Sequencing

Sequencing is concerned with determining both the

order in which jobs are processed at various work

centers and the order in which jobs are processed at

individual workstations within the work centers.

When work centers are heavily loaded, the order of

processing can be very important in terms of costs

associated with jobs waiting for processing and in

terms of idle time at the work centers.

14


Sequencing

There are a few more fractions in loading which are:

Sequencing Jobs Through Two Work Centers

To minimize the makespan for a group of jobs to be

processed on two machines or at two successive work

centers. It also minimizes the total idle time at the work

centers.

Sequence Jobs When Setup Times Are Sequence-

Dependent

To determine which sequence will result in the lowest total

setup time is to list each possible sequence and determine

its total setup time.

15


Sequencing Priority rules are simple heuristics used to select the order in which

the jobs will be processed. Some of the most common are listed below:

16


17

GANTT CHART

Gantt charts are used as visual aid for loading

and scheduling purposes.

The name was derived from Henry Gantt in the

early 1900s.

The purpose of Gantt charts is to organize and

clarify the actual or intended use of resources in

a time framework.

18

GANTT CHART

A time scale is represented horizontally and,

Resources to be scheduled are listed vertically.

The use of resources is reflected in the body of

the chart.

19

GANTT CHART

20

GANTT CHART

21

GANTT CHART

There are a number of different types of Gantt

charts.

Two of the most commonly used are:-

Load chart

Schedule chart.

22

GANTT CHART

Load Chart

A load chart depicts the loading and idle times

for a group of machines or a list of departments.

The chart shows when certain jobs are scheduled

to start and finish, and where to expect idle time.

23

GANTT CHART

Load Chart

24

GANTT CHART

Schedule Chart

There are two general approaches to scheduling:

forward scheduling and backward scheduling.

Forward scheduling means scheduling ahead

from a point in time.

Backward scheduling means scheduling

backward from a due date.

25

GANTT CHART

Forward scheduling is used if the issue is “How

long will it take to complete this job?”

Backward scheduling would be used if the issue

is “When is the latest job can be started and still

be completed by the due date?”

A manager often uses a schedule chart to monitor

the progress of jobs.

26

GANTT CHART

Schedule Chart

27

INPUT / OUTPUT CONTROL

Input / output (I/O) control refers to monitoring the work flow and queue length at work centers.

The purpose is to manage work flow so that queues and waiting times are kept under control.

A simple example of I/O control is the use of stoplights on some expressway on ramps.

These regulate the flow of entering traffic according to the current volume of expressway traffic. 28

INPUT / OUTPUT CONTROL

The following figure illustrates an input / output

report for a work center.

29

ASSIGNMENT METHOD OF LINEAR

PROGRAMMING

A special class of linear programming models

that assign tasks or jobs to resources.

Objective is to minimize cost or time.

Only one job (or worker) is assigned to one

machine (or project).

30


PROGRAMMING

Build a table of costs or time associated with

particular assignments

31


PROGRAMMING

1. Create zero opportunity costs by repeatedly

subtracting the lowest costs from each row and

column.

2. Draw the minimum number of vertical and

horizontal lines necessary to cover all the zeros

in the table. If the number of lines equals either

the number of rows or the number of columns,

proceed to step 4. Otherwise proceed to step 3.

32


PROGRAMMING

3. Subtract the smallest number not covered by a

line from all other uncovered numbers. Add the

same number to any number at the intersection

of two lines. Return to step 2.

4. Optimal assignments are at zero locations in

the table. Select one, draw lines through the

row and column involved, and continue to the

next assignment.

33


PROGRAMMING

34


PROGRAMMING

35


PROGRAMMING

36


PROGRAMMING

37

SEQUENCING

Specifies the order in which jobs should be

performed at work centers.

Priority rules are used to dispatch or sequence

jobs such as:

FCFS (First come, first served)

SPT (Shortest processing time)

EDD (Earliest due date)

CR (critical ratio)

S/O (slack per operation)

Rush

38

SEQUENCING

FCFS Jobs are processed in the order in which they arrive at a machine or work center.

SPT Jobs are processed according to processing time at a machine or work center, shortest

job first.

EDD Jobs are processed according to due date, earliest due date first.

CR Jobs are processed according to smallest ratio of time remaining until due date to

processing time remaining.

S/O Jobs are processed according to average slack time (time until due date minus

remaining time to process). Compute by dividing slack time by number of remaining operations, including the current one.

Rush Emergency or preferred customers first. 39

SEQUENCING

The rules generally rest on the following

assumptions:

The set of jobs is known; no new jobs arrive after

processing begins; and no jobs are canceled.

Setup time is independent of processing sequence.

Setup time is deterministic.

Processing time is deterministic rather than variable.

There will be no interruptions in processing such as

machine breakdowns, accidents, or work illness.

40

SEQUENCING

Example

Processing times (including setup times) and due dates for six jobs waiting to be processed at a work center are given in the following table. Determine the sequence of jobs, the average flow time, average days late, and average number of jobs at the work center, for each of these rules:

FCFS

SPT

EDD

CR

Job Processing Time (Days) Due Date (days)

A 2 7

B 8 16

C 4 4

D 10 17

E 5 15

F 12 18

41

SEQUENCING (SOLUTION)

a) The FCFS sequence is simple A-B-C-D-E-F. The measures of

effectiveness are (see table below):

1. Average flow time: 120/6 = 20 days.

2. Average tardiness: 54/6 = 9 days.

3. The makespan is 41 days. Average number of jobs at the

work center: 120/41=2.93.

Job Sequence Processing Time Flow Time Due Date Days Late (0 if negative)

A 2 2 7 0

B 8 10 16 0

C 4 14 4 10

D 10 24 17 7

E 5 29 15 14

F 12 41 18 23

41 120 54

42


b) Using the SPT rule, the job sequence is A-C-E-B-D-F (see the

following table). The resulting values for the three measures of

effectiveness are:

1. Average flow time: 108/6 = 18 days.

2. Average tardiness: 40/6 = 6.67 days.




A 2 2 7 0

C 4 6 4 2

E 5 11 15 0

B 8 19 16 3

D 10 29 17 12

F 12 41 18 23

41 108 40

43


c) Using EDD as the election criterion, the job sequence is C-A-E-

B-D-F. The measures of effectiveness are (see table):

1. Average flow time: 110/6 = 18.33 days.





C 4 4 4 0

A 2 6 7 0

E 5 11 15 0

B 8 19 16 3

D 10 29 17 12

F 12 41 18 23

41 110 38

44


d) Using the critical ratio we find:

At day 4 [C completed], the critical ratios are:

Job Sequence Processing Time Due Date Critical Ratio Calculation

A 2 7 (7-0)/2=3.5

B 8 16 (16-0)/8=2.0

C 4 4 (4-0)/4=1.0 (lowest)

D 10 17 (17-0)/10=1.7

E 5 15 (15-0)/5=3.0

F 12 18 (18-0)/12=1.5


A 2 7 (7-4)/2=1.5

B 8 16 (16-4)/8=1.5

C - - -

D 10 17 (17-4)/10=1.3

E 5 15 (15-4)/5=2.2

F 12 18 (18-4)/12=1.17 (lowest)

45


At day 16 [C and F completed], the critical ratios are:

At day 18 [C, F, and A completed], the critical ratios are:


A 2 7 (7-16)/2=-4.5 (lowest)

B 8 16 (16-16)/8=0.0

C - - -

D 10 17 (17-16)/10=0.1

E 5 15 (15-16)/5=-0.2

F - - -


A - - -

B 8 16 (16-18)/8=-0.25

C - - -

D 10 17 (17-18)/10=-0.10

E 5 15 (15-18)/5=-0.60 (lowest)

F - - -

46


At day 23 [C, F, A, and E completed], the critical ratios are:


A - - -

B 8 16 (16-23)/8=-0.875 (lowest)

C - - -

D 10 17 (17-23)/10=-0.60

E - - -

F - - -

47


The job sequence is C-F-A-E-B-D, and the resulting values for the

measures of effectiveness are:

1. Average flow time: 133/6 = 22.17 days.


3. The makespan is 41 days. Average number of jobs at the work center:

133/41=3.24.


C 4 4 4 0

F 12 16 18 0

A 2 18 7 11

E 5 23 15 8

B 8 31 16 15

D 10 41 17 24

41 133 58

48


The results of these four rules are summarized

below:

Rule Average Flow Time (days) Average Tardiness (days)

Average Number of Jobs at the

Work Center

FCFS 20.00 9.00 2.93

SPT 18.00 6.67 2.63

EDD 18.33 6.33 2.68

CR 22.17 9.67 3.24

49


Use S/O (slack per operation) rule to schedule the following jobs. Note

that processing time includes the time remaining for the current and

subsequent operations. In addition, you will need to know the number of

operations remaining, including the current one.

Job Remaining Processing Time Due Date

Remaining Number of

Operations

A 4 14 3

B 16 32 6

C 8 8 5

D 20 34 2

E 10 30 4

F 18 30 2

50


Solution: Determine the difference between the due date and the processing time for each operation. Divide the amount by the number of remaining operations, and rank them from low to high. This yields the sequence of jobs:

The indicated sequence is C-B-A-E-F-D

Job Remaining Processing Time Due Date Slack Remaining Number of Operations Ratio Rank

A 4 14 10 3 3.33 3

B 16 32 16 6 2.67 2

C 8 8 0 5 0.00 1

D 20 34 14 2 7.00 6

E 10 30 20 4 5.00 4

F 18 30 12 2 6.00 5

51

SEQUENCING JOBS THROUGH TWO WORK

CENTER

Johnson's rule is a technique that managers can

use to minimize the makespan for a group of jobs

to be processed on two machines or at two

successive work centers (sometimes referred to as

a two-machine flow shop).

It also minimizes the total idle time at the work

centers.

52


CENTER

For the technique to work, several conditions

must be satisfied:

1. Job time (including setup and processing) must be known and

constant for each job at each work center.

2. Job times must be independent of the job sequence.

3. All jobs must follow the same two-step work sequence.

4. Job priorities can not be used.

5. All units in a job must be completed at the first work center

before the job moves on to the second work center.

53


CENTER

Determination of the optimum sequence involves

these steps:

1. List the jobs and their times at each work center.

2. Select the job with the shortest time. If the shortest time is at

the first work center, schedule that job first; if the time is at

the second work center, schedule the job last. Break ties

arbitrarily.

3. Eliminate the job and its time from further consideration.

4. Repeat steps 2 and 3, working toward the center of the

sequence until all jobs have been scheduled

54


CENTER

Example: A group of six jobs is to be processed through a two-machine

flow shop. The first operation involves cleaning and the second involves

painting. Determine a sequence that will minimize the total completion

time for this group of jobs. Processing times are as follows:

Processing Time (Hours)

Job Work Center 1 Work Center 2

A 5 5

B 4 3

C 8 9

D 2 7

E 6 8

F 12 15

55


CENTER

Solution:

a. Select the job with the shortest processing time. It is job D

with a time of 2 hours.

b. Since the time is at the first center, schedule job D first.

Eliminate job D from further consideration.

c. Job B has the next shortest time. Since it is at the second

work center, schedule it last and eliminate job B from further

consideration. We now have:

1st 2nd 3rd 4th 5th 6th

D B

56


CENTER

d. The remaining jobs and their times are:

Note that there is a tie for the shortest remaining time: job A has the

same time at each work center. It makes no difference, then, whether

we place it toward the beginning or the end of the sequence. Suppose

it is placed arbitrarily toward the end. We now have

Processing Time (Hours)

Job Work Center 1 Work Center 2

A 5 5

C 8 9

E 6 8

F 12 15


D A B

57


CENTER

e. The shortest remaining time is 6 hours for job E

at work center 1. Thus, schedule that job toward

the beginning of the sequence (after job D).

Thus,


D E A B

58


CENTER

f. Job C has the shortest time of the remaining

two jobs. Since it is for the first work center,

place it third in the sequence. Finally, assign

the remaining job (F) to the fourth position and

the result is:


D E C F A B

59


CENTER

g. One way to determine the throughput time and idle times at the work

centers is to construct a chart:

Thus, the group of jobs will take 51 hours to complete. The second work

center will wait 2 hours for its first job and also wait 2 hours after

finishing job C. Center 1 will be finished in 37 hours. Of course, idle

periods at the beginning or end of the sequence could be used to do other

jobs or for maintenance or setup/teardown activities.

60

SEQUENCING JOBS WHEN SETUP TIMES

ARE SEQUENCE- DEPENDENT

The simplest way to determine which sequence

will result in the lowest total setup time is to list

each possible sequence and determine its total

setup time.

As the number of jobs increases, a manager

would use a computer to generate the list and

identify the best alternative(s).

61



Example:

Resulting following job setup time (hrs.) is

Setup time (hrs) A B C

If the proceding job is

A 3 - 6 2

B 2 1 - 4

C 2 5 3 -

62



Solution:

B-A-C.

Sequence Setup Time Total

A-B-C 3+6+4= 13

A-C-B 3+2+3= 8

B-A-C 2+1+2= 5

B-C-A 2+4+5= 11

C-A-B 2+5+6= 13

C-B-A 2+3+1= 6

63

EXERCISE 1. Define Gantt chart and cycle time.

2. A manager has to verify which priority methods than can be chosen to be

implemented in a cooper stamping company. Table below showed the processing

time and due date to complete the assigned project.

64

Job Processing Time (day) Due Date (day)

H 9 23

I 3 15

J 8 18

K 2 6

i. Determine the sequence jobs for each rule using priority methods of DD,

SPT and FCFS.

ii. Explain which priority method is the best.

Man/Jobs A B C D

I 8 10 17 9

II 3 8 5 6

III 10 12 11 9

IV 6 13 9 7

3. Four persons A, B, C and D are to be assigned four jobs I, II, III and IV. The cost matrix is

given as under, find the proper assignment.

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