chapter six facilities layout chapter 6 facilities layout

CHAPTER SIXFACILITIES LAYOUT

Chapter 6

Facilities Layout


MTSU Management 362 6-2

• 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 exiting layout



Inefficient operations

For Example:

High CostBottlenecks

Changes in the designof products or services

The introduction of newproducts 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



Product Layout (1 of 3)

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

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

• Examples include production lines and assembly lines



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

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

Product Layout (2 of 3)

Raw materialsor customer

Finished item

Station 2

Station 3

Station 4

Material and/or labor

Station 1






Product Layout (3 of 3)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



1

2

3

4

56

7

8

9

10

InOut

Workers

Figure 6-3

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



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 Layout - work travels to dedicated process centers

Milling

Assembly& Test Grinding

Drilling Plating

Process Layout (2 of 3)



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 Layouts

• Cellular Manufacturing– Layout in which machines are grouped into a cell that can process items that have

similar processing requirements

• Group Technology– The grouping into families of items(parts) with similar design or manufacturing

characteristics



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 6-5



Work Cells

• A hybrid between a process-oriented and product-oriented layouts

• Group technology identifies a family of items that require similar processing

• 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 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



Other 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

– 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– 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)

• Required tasks are assigned to work stations

• The objective 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 workers 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



Line Balancing Procedure (1 of 6)

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

Determine the selection heuristic (rule of thumb) that may be used to help with the assignments



Some Heuristic (Intuitive) RulesLine Balancing Procedure (2 of 6)

• 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




Open a new station with the full cycle time remaining

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




For a task to be feasible, 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




If there is only one feasible task, assign it to the station. If there is more than one feasible task, use the heuristic (step 2) to determine which task to assign. Reduce the station’s remaining cycle time by the estimated time for the assigned task. Return to step 4.




If there are no feasible tasks, assignments to that station are complete. Go back to step 3.

Stop when all tasks have been assigned to stations



D

OTCT;

day)per (units rate demand desired

dayper timeoperating= timeCycle

CT

tN;

timecycle

ifor task time=ons workstatiofnumber Minimum min

1

m

i

x100 time)(cyclestations)x ofnumber (actual

cycleper timeIdle= timeidle of Percentage

CT

OT

timecycle

dayper timeoperatingcapacityOutput

Line Balancing Relationships



1.4

a0.5

b

0.8

e

0.5

h

c

d

f

g

0.6 0.5

0.7

1.0

Return

The Precedence DiagramProblem 2, page 299



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

• 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, 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 C

Figure 6-10



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



ProcessLayout!!!

ProductLayout!!!

chapter six facilities layout chapter 6 facilities layout

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