Reid & Sanders, Operations Management© Wiley 2002
Facility Layout 10C H A P T E R
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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
Page 3Reid & Sanders, Operations Management© Wiley 2002
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
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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
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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
Page 6Reid & Sanders, Operations Management© Wiley 2002
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
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Group Technology
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Traditional Process Layout
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Manufacturing Cells
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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:
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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
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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
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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
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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
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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
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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
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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
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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
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Compute Efficiency
%7.91100603
165Efficiency
%3.8%7.91%100delay Balance
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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
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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.