reid & sanders, operations management © wiley 2002 facility layout 10 c h a p t e r

Reid & Sanders, Operations Management© Wiley 2002

Facility Layout 10C H A P T E R


Learning Objectives

• Define facility layout• Describe different types of layouts• Compare process & product layouts• Describe the design process for different

layouts• Explain the advantages of hybrid layouts• Define group technology & manufacturing

cells


Facility Layout

• Layout planning is determining the best physical arrangement of resources within a facility

• Process layouts:– Group similar resources together– Emphasis is on flexibility

• Product layouts:– Designed to produce a specific product efficiently – Emphasis is on efficiency


Process Layouts

• General purpose & flexible resources

• Lower capital intensity & automation

• Higher labor intensity

• Processing rates are slower

• Material handling costs are higher

• Scheduling resources & work flow is more complex


Product Layouts

• Specialized equipment

• High capital intensity & wide use of automation

• Processing rates are faster

• Material handling costs are lower

• Less space required for inventories

• Less volume or design flexibility


Hybrid Layouts

• Combine elements of both product & process layouts– Maintain some of the efficiencies of

product layouts– Maintain some of the flexibility of process

layouts

• Example: group technology & manufacturing cells


Group Technology


Traditional Process Layout


Manufacturing Cells


Designing Process Layouts

• Gather information:– Space needed, space available, importance of

proximity between various units

• Develop alternative block plans:– Using trail-and-error or decision support tools

• Compare alternatives & choose a detailed layout:


Comparing Alternatives

• Load-distance measures– Load: # of trips, weight moved, $-value moved– Distance: rectilinear distance (using north-south &

east-west movements)

• REL charts: – Management opinion on strength of relationships

• Software tools:– CRAFT: computerized relative allocation of

facilities technique– ALDEP: automated layout design program


Designing Product Layouts

• Identify tasks & immediate predecessors• Determine the desired output rate• Calculate the necessary cycle time• Compute the theoretical minimum number of

workstations• Assign tasks to workstations• Compute efficiency, idle time & balance delay


Cycle Time

• The amount of time each workstation is allowed to complete its tasks

• Limited by the bottleneck task (the longest task to be performed):

units/dayin output desired

yseconds/dain timeavailablenit)(seconds/u timeCycle

task timebottleneck

timeavailableoutput Maximum


Theoretical MinimumNumber of Workstations

• TM = number of stations needed to achieve 100% efficiency (every second is used)

• Always round up (no partial workstations)• Serves as a lower bound for our analysis

timecycle

task timesTM


Assigning Tasks to Workstations

• Start at the first station & choose the longest eligible task (tasks with no unassigned predecessors)

• Continue adding the longest eligible task that fits without going over the desired cycle time

• When no additional tasks can be added, begin assigning tasks to the next workstation

• Continue until all tasks are assigned


Compute Efficiency& Balance Delay

• Efficiency is the ratio of productive time to total time:

• Balance delay:

100

timecyclestations ofnumber

task times%Efficency

Efficency - 100 %delay Balance


Frozen Pizza Example

• Desired output is 60 pizzas/hour– Cycle time is (3600 seconds/hour)/(60 units/hour)– Cycle time = 60 seconds/unit

Task Description Predecessor Task TimeA Roll dough None 50B Place on cardboard A 5C Spread sauce B 25D Sprinkle cheese C 15E Add pepperoni D 12F Add sausage D 10G Add mushrooms D 15H Shrink-wrap pizza E, F, & G 18I Pack in box H 15

Total: 165


Assign Tasks

Workstation Eligible task Task Selected Task time Idle time

A A 50 10

B B 5 5

C C 25 35

D D 15 20

E, F, G G 15 5

E, F E 12 48

F F 10 38

H H 18 20

I I 15 5

1

2

3


Compute Efficiency

%7.91100603

165Efficiency

%3.8%7.91%100delay Balance


Other Considerations

• Shape of the line (S, U, O, L):– Share resources, enhance communication

& visibility, impact location of loading & unloading

• Paced versus unpaced lines– Paced lines use an automatically enforced

cycle time

• Single or mixed-model lines


The End

Copyright © 2002 John Wiley & Sons, Inc. All rights reserved. Reproduction or translation of this work beyond that permitted in Section 117 of the 1976 United State Copyright Act without the express written permission of the copyright owner is unlawful. Request for further information should be addressed to the Permissions Department, John Wiley & Sons, Inc. The purchaser may make back-up copies for his/her own use only and not for distribution or resale. The Publisher assumes no responsibility for errors, omissions, or damages, caused by the use of these programs or from the use of the information contained herein.

reid & sanders, operations management © wiley 2002 facility layout 10 c h a p t e r

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