Process Selection And Facility Layout 13e3f

6-2

Process Selection and Facility Layout

Operations Management

William J. Stevenson

8th edition

6-3

Process Selection and Facility Layout

CHAPTER

6

Process Selection and Facility Layout

McGraw-Hill/Irwin

Operations Management, Eighth Edition, by William J. Stevenson Copyright © 2005 by The McGraw-Hill Companies, Inc. All rights reserved.

6-4

Process Selection and Facility Layout

Introduction



Process selection 



Deciding on the way production of goods or services will be organized

Major implications 

Capacity planning  Layout of facilities  Equipment  Design of work systems

6-5

Process Selection and Facility Layout

Process Selection and System Design

Figure 6.1

Forecasting

Capacity Planning

Product and Service Design

Technological Change

Facilities and Equipment

Layout Process Selection

Work Design

6-6

Process Selection and Facility Layout

Process Strategy

• Key aspects of process strategy –

Capital intensive – equipment/labor

–

Process flexibility

–

Adjust to changes –

Design

–

Volume

–

technology

6-7

Process Selection and Facility Layout

Process Selection



Variety 



Flexibility 



Batch

How much

What degree

Job Shop

Repetitive

Volume 

Expected output

Continuous

6-8

Process Selection and Facility Layout

Process Types



Job shop 



Batch 



Moderate volume

Repetitive/assembly line 



Small scale

High volumes of standardized goods or services

Continuous 

Very high volumes of non-discrete goods

6-9

Process Selection and Facility Layout

Product – Process Matrix

Figure 6.2 Process Type

Job Shop

Appliance repair Emergency room

Not feasible Commercial bakery

Batch

Classroom Lecture Automotive assembly

Repetitive

Automatic carwash

Continuous (flow)

Not feasible

Oil refinery Water purification

6-10 Process Selection and Facility Layout

Product – Process Matrix

Figure 6.2 (cont’d) Dimension Job variety

Very High

Moderate

Low

Very low

Process flexibility

Very High

Moderate

Low

Very low

Unit cost

Very High

Moderate

Low

Very low

Volume of output

Very High

Low

High

Very low

6-11 Process Selection and Facility Layout

Automation



Automation: Machinery that has sensing and control devices that enables it to operate 

Fixed automation  Programmable automation

6-12 Process Selection and Facility Layout

Automation

• Computer-aided design and manufacturing systems (CAD/CAM) • Numerically controlled (NC) machines • Robot • Manufacturing cell • Flexible manufacturing systems(FMS) • Computer-integrated manufacturing (CIM)

6-13 Process Selection and Facility Layout

Facilities Layout



Layout: the configuration of departments, work centers, and equipment, with particular emphasis on movement of work (customers or materials) through the system

6-14 Process Selection and Facility Layout

Importance of Layout Decisions



Requires substantial investments of money and effort  Involves long-term commitments  Has significant impact on cost and efficiency of short-term operations

6-15 Process Selection and Facility Layout

The Need for Layout Decisions

Inefficient operations For Example:

High Cost Bottlenecks

Changes in the design of products or services

Accidents The introduction of new products or services

Safety hazards

6-16 Process Selection and Facility Layout

The Need for Layout Design (Cont’d) Changes in environmental or other legal requirements

Changes in volume of output or mix of products Morale problems

Changes in methods and equipment

6-17 Process Selection and Facility Layout

Basic Layout Types



Product layouts



Process layouts



Fixed-Position layout



Combination layouts

6-18 Process Selection and Facility Layout

Basic Layout Types



Product layout 



Process layout 



Layout that uses standardized processing operations to achieve smooth, rapid, highvolume flow Layout that can handle varied processing requirements

Fixed Position layout 

Layout in which the product or project remains stationary, and workers, materials, and equipment are moved as needed

6-19 Process Selection and Facility Layout

Product Layout

Figure 6.4

Raw materials or customer Material and/or labor

Station 1 Material and/or labor

Station 2 Material and/or labor

Station 3

Station 4

Material and/or labor

Used for Repetitive or Continuous Processing

Finished item

6-20 Process Selection and Facility Layout

Advantages of Product Layout



High rate of output  Low unit cost  Labor specialization  Low material handling cost  High utilization of labor and equipment  Established routing and scheduling  Routing ing and purchasing

6-21 Process Selection and Facility Layout

Disadvantages of Product Layout



Creates dull, repetitive jobs  Poorly skilled workers may not maintain equipment or quality of output  Fairly inflexible to changes in volume  Highly susceptible to shutdowns  Needs preventive maintenance  Individual incentive plans are impractical

6-22 Process Selection and Facility Layout

A U-Shaped Production Line

Figure 6.6

In

1

2

3

4 5

Workers

6 Out

10

9

8

7

6-23 Process Selection and Facility Layout

Process Layout

Figure 6.7

Process Layout (functional) Dept. A

Dept. C

Dept. E

Dept. B

Dept. D

Dept. F

Used for Intermittent processing Job Shop or Batch

6-24 Process Selection and Facility Layout

Product Layout

Figure 6.7 (cont’d)

Product Layout (sequential) Work Station 1

Work Station 2

Work Station 3

Used for Repetitive Processing Repetitive or Continuous

6-25 Process Selection and Facility Layout

Advantages of Process Layouts



Can handle a variety of processing requirements  Not particularly vulnerable to equipment failures  Equipment used is less costly  Possible to use individual incentive plans

6-26 Process Selection and Facility Layout

Disadvantages of Process Layouts 

In-process inventory costs can be high  Challenging routing and scheduling  Equipment utilization rates are low  Material handling slow and inefficient  Complexities often reduce span of supervision  Special attention for each product or customer  ing and purchasing are more involved

6-27 Process Selection and Facility Layout

Cellular Layouts



Cellular Production 



Layout in which machines are grouped into a cell that can process items that have similar processing requirements

Group Technology 

The grouping into part families of items with similar design or manufacturing characteristics

6-28 Process Selection and Facility Layout

Functional vs. Cellular Layouts

Table 6.3 Dimension

Functional

Cellular

Number of moves between departments

many

few

Travel distances

longer

shorter

Travel paths

variable

fixed

Job waiting times

greater

shorter

Throughput time

higher

lower

Amount of work in process

higher

lower

Supervision difficulty

higher

lower

Scheduling complexity

higher

lower

Equipment utilization

lower

higher

6-29 Process Selection and Facility Layout

Other Service Layouts



Warehouse and storage layouts  Retail layouts  Office layouts

6-30 Process Selection and Facility Layout

Design Product Layouts: Line Balancing

Line Balancing is the process of asg tasks to workstations in such a way that the workstations have approximately equal time requirements.

6-31 Process Selection and Facility Layout

Cycle Time

Cycle time is the maximum time allowed at each workstation to complete its set of tasks on a unit.

6-32 Process Selection and Facility Layout

Determine Maximum Output OT O utput capacity = CT O T  operating tim e per day D = Desired output rate OT CT = cycle tim e = D

6-33 Process Selection and Facility Layout

Determine the Minimum Number of Workstations Required

N =

(D)( t) OT

 t = sum of task times

6-34 Process Selection and Facility Layout

Precedence Diagram

Figure 6.10

Precedence diagram: Tool used in line balancing to display elemental tasks and sequence requirements 0.1 min.

1.0 min.

a

b c

0.7 min.

d 0.5 min.

A Simple Precedence Diagram

e 0.2 min.

6-35 Process Selection and Facility Layout

Example 1: Assembly Line Balancing 

Arrange tasks shown in Figure 6.10 into three workstations. 

Use a cycle time of 1.0 minute  Assign tasks in order of the most number of followers

6-36 Process Selection and Facility Layout

Example 1 Solution

Eligible

Assign Task

1.0 0.9 0.2

a, c c none

a c -

0.9 0.2

2

1.0

b

b

0.0

3

1.0 0.5 0.3

d e -

d e -

0.5 0.3

Workstation 1

Time Remaining

Revised Time Remaining

Station Idle Time

0.2 0.0 0.3 0.5

6-37 Process Selection and Facility Layout

Calculate Percent Idle Time

Idle time per cycle Percent idle time = (N)(CT)

Efficiency = 1 – Percent idle time

6-38 Process Selection and Facility Layout

Line Balancing Rules

Some Heuristic (intuitive) Rules: 

Assign tasks in order of most following tasks. 



Count the number of tasks that follow

Assign tasks in order of greatest positional weight. 

Positional weight is the sum of each task’s time and the times of all following tasks.

6-39 Process Selection and Facility Layout

Example 2

0.2

0.2

0.3

a

b

e

0.8

0.6

c

d

f

g

h

1.0

0.4

0.3

6-40 Process Selection and Facility Layout

Solution to Example 2

Station 1

a

b

Station 2

Station 3

e f

c

Station 4

d

g

h

6-41 Process Selection and Facility Layout

Parallel Workstations

1 min.

30/hr.

1 min.

30/hr.

2 min.

30/hr.

1 min.

30/hr.

Bottleneck 30/hr. 1 min.

60/hr.

1 min.

30/hr.

1 min.

1 min. 30/hr. 1 min.

Parallel Workstations

30/hr.

60/hr.

6-42 Process Selection and Facility Layout

Deg Process Layouts

Information Requirements: 1. List of departments 2. Projection of work flows 3. Distance between locations 4. Amount of money to be invested 5. List of special considerations 6. Location of key utilities

6-43 Process Selection and Facility Layout

Example 3: Interdepartmental Work Flows for Assigned Departments

Figure 6.12

30 1

A

170

B

3

10 0

C

2

6-44 Process Selection and Facility Layout



Author’s note: 

The following three slides are not in the 8e, but I like to use them for alternate examples.

6-45 Process Selection and Facility Layout

Process Layout Milling

Assembly & Test

Grinding

Drilling

Plating

Process Layout - work travels to dedicated process centers

6-46 Process Selection and Facility Layout

Functional Layout

222 444

Mill

111 333 111 333

Lathes

222 111 444

222

Drill

Grind

3333

1111 2222

Heat treat

Assembly 111

Gear cutting

111 444

6-47 Process Selection and Facility Layout

-1111

Lathe

Mill

Drill

222222222

Mill

3333333333

Lathe Mill

44444444444444

Drill

Mill

Heat treat

Gear -1111 cut

Heat treat

Grind - 2222

Heat treat

Grind - 3333

Drill

Gear - 4444 cut

Assembly

Cellular Manufacturing Layout