Chapter 6 Process Selection and Facility Layout. Management 3620Chapter 6 Process Selection and Facility Layout6-2 Process Selection How an organization

Chapter 6Process Selection

and Facility Layout

Management 3620 Chapter 6 Process Selection and Facility Layout 6-2

Process Selection

• How an organization chooses to produce its goods or provide its services

• Key aspects– make or buy decisions

– capital intensity

– process flexibility


Forecasting

Product and service design

Capacity planning

Facilities andEquipment

Layout

Work design

Processselection

Figure 6-1

Technologicalchange

Technologicalchange

Process Selection and System Design


Process Selection and Capacity Planning

• Make or Buy?– Available capacity

– Expertise

– Quality considerations

– The nature of demand

– Cost


Key Factors inProcess Selection

• Variety– How much

• Flexibility– What degree

• Volume – Expected output


Basic Process Types

• Continuous Processing• Repetitive/Assembly

– Semicontinuous

• Intermittent/Batch Processing• Job Shops

– Small runs

• Projects– Nonroutine jobs


Job Shop

• Used when processing a high-variety goods or services with low volumes

• Processing requirements can differ with the job

• Flow of jobs is intermittent

• Processes must be highly flexible

• Workers must be highly skilled and highly flexible


Batch

• Appropriate for moderate variety of goods or services with moderate volumes

• Processing is intermittent

• Process flexibility and worker skills do not need to be as high as with a job shop


Repetitive (Assembly)

• Used for more standardized goods and services with higher volumes

• Process flexibility is small

• Skill levels are generally low


Continuous

• Used for highly standardized goods and services with very higher volume

• There is no process flexibility

• Required skill levels are generally low


Project

• Unique effort to be accomplished with limited resources, i.e., the volume is one

• Large scale effort

• Process flexibility and worker skills can range from low to high


ProductVariety

High Moderate Low Very Low

Equipmentflexibility

High Moderate Low Very Low

LowVolume

ModerateVolume

HighVolume

Very highVolume

JobShop

Batch

Repetitiveassembly

ContinuousFlow

Variety, Flexibility, & Volume


HighVolume,

HighStandardization

Flexibility-Quality Dependability-Cost

ContinuousFlow

AssemblyLine

Batch

JobShop

LowVolumeOne of a

Kind

MultipleProducts,

LowVolume

Few MajorProducts,

HigherVolume

CommercialPrinter

HeavyEquipment

SugarRefinery

Flexibility-Quality

DependabilityCost

Product-Process Life Cycle Matrix

AutomobileAssembly


Automation (1 of 2)

• Processes that have sensing and control devices that enable it to operate automatically

• Three kinds– fixed– programmable

• computer-aided design and manufacturing systems (CAD/CAM)

• numerically controlled (NC) machines• robot


Automation (2 of 2)

– flexible• manufacturing cells• flexible manufacturing systems (FMS)

– Processes and material handling controlled by computers

• computer-integrated manufacturing (CIM)

– Links various parts of the organization to achieve rapid response


Service Process Design• Service blueprinting

– A method used in service design to describe and analyze a proposed service.

• Steps– Establish boundaries– Identify steps involved– Prepare a flowchart– Identify potential failure points– Establish a time frame– Analyze profitability


Facilities Layout• The arrangement or configuration of

departments, work centers, and equipment within the confines of a building or area

• Focuses on the movement of work (customers or material) through the system

• May involve designing a completely new layout or redesigning an existing 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


Inefficient operations

For Example:

High CostBottlenecks

Changes in the designof products or services

The introduction ofnew products or services

Accidents

Safety hazards

The Need for Layout Decisions (1 of 2)


Changes inenvironmentalor other legalrequirements

Changes in volume ofoutput or mix of

products

Changes in methodsand equipment

Morale problems

The Need for Layout Designs (2 of 2)


Basic Layout Types

• Product • Process • Fixed Position• Combination• Cellular• Other service layouts

– warehouse and storage– retail– office


Basic Layout Types

• Product (continuous, repetitive)• Process (job shop)• Fixed Position (project)• Combination• Cellular (batch)• Other service layouts

– warehouse and storage– retail– office


Product Layout (1 of 3)

• Uses standardized processing operations to achieve smooth, rapid, high-volume flow

• Work stations or areas are arranged according to the fixed sequence of tasks required to produce a product or provide a service

• Examples include production lines and assembly lines



Raw materialsor customer

Finished item

Station 2

Material and/or labor

Station 3


Station 4



Station 1

Layout design involves assigning one or more of the tasks (time) required to make the product/service to work stations

Work stations are arranged so that the output of one is an input to the next, i.e., a series connection



Advantages• High rate of output• Low unit cost• Labor specialization• Specialized equipment• Low material-handling cost• High utilization of labor and

equipment• Routing and scheduling

designed initially• Accounting, purchasing, and

inventory control fairly routine

Disadvantages• Dull, repetitive jobs• Unskilled workers• Fairly inflexible• Susceptible to

shutdowns• PM, quick repairs, and

spare equipment parts• Incentive plan

impractical


A U-Shaped Production Line

• More compact than the straight production line

• Permits increased communication among workers

• Increased flexibility in work assignments

• Materials enter at about the same place that finished products exit

1

2

3

4

56

7

8

9

10

InOut

Workers

Figure 6-7


Process Layout (1 of 3)

• Layout that can handle varied processing requirements– each product/service may require a

different sequence of operations (routing)

– wide variety of products/services in small volumes

• Work areas are arranged according to the processes being performed, i.e., like processes are located together


Process (Functional) Layout(2 of 3)

Gearcutting

Mill Drill

Lathes

Grind

Heattreat

Assembly

111

111

1111111

111111

444444

444

44444

333

333

3333

333333333

3333

33

222 222

2222

222

2222

2


Process Layouts (3 of 3)

Advantages• Handles a variety of

processing requirements• Not vulnerable to

equipment failure• General-purpose

equipment• Individual incentive

systems possible

Disadvantages• In-process inventory can be

high• Routing and scheduling

challenging• Equipment utilization low• Material-handling cost high• High supervision costs• High unit cost • Accounting, purchasing, and

inventory control challenging


Fixed-Position Layout

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

• Used in large construction projects

• Scheduling of resources is an issue in this type of layout


Combination Layout

• Most real-world layouts are some combination or variation of product and process layouts

• The mix that makes up the combination is determined by the needs of the customer


Cellular Layout (1 of 2)

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

• A hybrid between a process and product layouts

• Group technology identifies a family of items that have similar processing requirements


Cellular Layout (2 of 2)

• The processes shared by the members of a family form a small product layout

• Volume of the entire family justifies the dedication of resources

• Requires a high level of training and flexibility on the part of the employees


Cellular Manufacturing Layout

-1111 -1111

222222222 - 2222

Ass

emb

ly

3333333333 - 3333

44444444444444 - 4444

Lathe

Lathe

Mill

Mill

Mill

Mill

Drill

Drill

Drill

Heat treat

Heat treat

Heat treat

Gear cut

Gear cut

Grind

Grind

Figure 6-9


Cellular Layouts —Some Advantages

• Reduced work-in-process inventory

• Less floor space required

• Reduced raw material and finished goods inventories required

• Reduced direct labor costs

• Heightened sense of employee participation

• Increased utilization of equipment machinery

• Reduced investment in machinery and equipment


Service Layouts• Warehouse and storage layouts

– frequency of order an important factor– number and width of aisles– height of storage racks– material-handling methods

• Retail layouts– an objective is to maximize profitability per

square foot of shelf space– traffic patterns, traffic flow and product

placement are important factors

• Office layouts


Information Needed toDesign a Good Layout (1 of 2)

• An understanding of capacity of the area and the space and other requirements for processes

• Identification of the cost of moving materials between the various work areas

• Selection of appropriate material handling equipment


Information Needed toDesign a Good Layout (2 of 2)

• Identification and understanding of the requirements for information flow to support the flow of work

• Decisions regarding environment and aesthetics


Designing Product Layouts (1 of 3)

• The tasks required to make the product are distributed or assigned to the work stations

• The objective when making these assignments is to minimize the workers’ idle time therefore idle time costs, and meet the required production rate for the line

Raw materialsor customer

Finished item

Station 2

Station 3

Station 4


Station 1






• Ideally, each work station would be assigned the same amount of work (time), i.e., the required work would be balanced among the work stations– all workers would complete their

assigned tasks at the same time (assuming they start their work simultaneously)

– this would result in no idle time



• Unfortunately there are conditions that can prevent the achievement of a perfectly balanced line– The estimated times for tasks

– The precedence relationships for the tasks

– The combinatoric nature of the problem


Inputs Needed To Design a Product Layout (1 of 2)

• The production rate required from the product layout or the cycle time.– The cycle time is the reciprocal of the

production rate and visa versa

• All of the tasks required to make the product– It is assumed that these tasks can not

be divided further


Inputs Needed To Design a Product Layout (2 of 2)

• The estimated time to do each task

• The precedence relationships between the tasks– determined by the technical constraints

imposed by the product design

– displayed as a network known as a precedence diagram


1.4

a0.5

b

0.8

e

0.5

h

c

d

f

g

0.6 0.5

0.7

1.0

The Precedence DiagramProblem 2, page 263


Line Balancing Procedure

If not provided, find the cycle time. Remember the cycle time is the reciprocal of the production rate. The cycle time is expressed in the same time units as the estimated task times


D

OT=CT;

rate demand desired

time operating=time Cycle

CT

tΣ=N ;

time cycle

i task for timeΣ

=ons workstatiof number Minimum

min

100 x time) (cycle x stations) of number (actual

cycle per time Idle

=time idle of Percentage

CT

OT=

time cycle

day per time operating=capacityOutput

Line Balancing Relationships


nitu1.8min./units/hour 33.3

min./hour 60

D

OT=time Cycle

stations 4 or 3.33onmin./stati 1.8

min./unit 6.0

CT

tNmin

Problem 2, page 263


Line Balancing Procedure Determine the selection heuristic (rule of

thumb) that may be used to help with the assignments

Examples of heuristic (intuitive) rules– Assign tasks in order of longest task time– Assign tasks in order of most following

tasks– 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


Cycle time = 60/33.33 = 1.8 minutes/unit

Selection heuristic: positional weight (part b)

Open the first work station with the full cycle time remaining unassigned

WorkStation

RemainingCycleTime

EligibleTasks

SelectedTasks

1 1.8

Design Procedure


1.4

a0.5

b

0.8

e

0.5

h

c

d

f

g

0.6 0.5

0.7

1.0

The Precedence DiagramProblem 2, page 263

1.0

1.52.3

2.2

1.64.66.0

0.5

Positional Weight


Line Balancing Procedure

Determine which unassigned tasks are eligible, i.e., can be assigned to this work station at this time

For a task to be eligible, two conditions must be met– All tasks that precede that task must

have already been assigned– The estimated task time must be

equal to or less than the remaining cycle time for that work station


Design Procedure

If there is only one eligible task, assign it to the work station.

If there is more than one eligible task, use the selection heuristic (step 2) to determine which eligible task to assign.

WorkStation

RemainingCycleTime

EligibleTasks

AssignedTasks

1 1.8 a


WorkStation

RemainingCycleTime

EligibleTasks

AssignedTasks

1 1.8 a a1.8-1.4=.4

Design Procedure

Reduce the station’s remaining cycle time by the estimated time for the assigned task. Return to step 4.


If there are no eligible tasks, assignments to that work station are complete. Open the next work station and go back to step 4.

WorkStation

RemainingCycleTime

EligibleTasks

AssignedTasks

1 1.8 a a1.8-1.4=.4 none none

Design Procedure


WorkStation

RemainingCycleTime

EligibleTasks

AssignedTasks

1 1.8 a a1.8-1.4=.4 none none

2 1.8

Design Procedure


1 min.2 min.1 min.1 min. 30/hr. 30/hr. 30/hr. 30/hr.

1 min.

2 min.

1 min.1 min. 60/hr.

30/hr. 30/hr.

60/hr.

2 min.

30/hr.30/hr.

Parallel Workstations

Bottleneck

Parallel Workstations1 min.


Designing Process Layouts• Determine the relative positioning of the

departments or work centers• Arrangement can be influenced by

external factors• Typically when one department is

moved at least one other department will have to move

• This results in a combinatoric problem, i.e., a large number of possible arrangements


Measures of Effectiveness

• A major objective is to find an arrangement which minimizes material-handle cost, distance traveled, or time

• Other concerns include– cost of changing an existing layout– expected operating costs– amount of effective capacity created– ease of modifying the system


Information Requirements• Dimensions of departments;

dimension of building• Forecast of flows between each pair

of work centers• Distance between locations and

material-handling cost/unit of distance

• Financial resources• Special considerations


Interdepartmental Work Flows for Assigned Departments

1 3 2

30

170 100

A B CFigure 6-14


Alternative Approaches

• Closeness ratings– ranks the importance that each pair of

departments be close together

– rating can incorporate qualitative and quantitative information

– allows the consideration of areas not in the flow of “material”

• Computer analysis

Documents

Chapter 6 Process Selection and Facility Layout. Management 3620Chapter 6 Process Selection and Facility Layout6-2 Process Selection How an organization