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Production and Operations Management
Norman Gaither Greg Frazier
Slides Prepared by John Loucks
1999 South-Western College Publishing
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Chapter 8
Facility Layout:Manufacturing and Services
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Overview
Introduction Manufacturing Facility Layouts
Analyzing Manufacturing Facility Layouts
Service Facility Layouts Wrap-Up: What World-Class Producers Do
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Introduction
Facility layout means planning: for the location of all machines, utilities, employee
workstations, customer service areas, material
storage areas, aisles, restrooms, lunchrooms,
internal walls, offices, and computer rooms
for the flow patterns of materials and people
around, into, and within buildings
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Locate All Areas In and Around Buildings
Equipment Work stations
Material storage
Rest/break areas Utilities
Eating areas
Aisles Offices
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Characteristics of the Facility Layout Decision
Location of these various areas impacts the flowthrough the system.
The layout can affect productivity and costs generated
by the system.
Layout alternatives are limited by
the amount and type of space required for the
various areas
the amount and type of space available
the operations strategy
. . . more
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Characteristics of the Facility Layout Decision
Layout decisions tend to be: Infrequent
Expensive to implement
Studied and evaluated extensively Long-term commitments
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Manufacturing Facility Layouts
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Basic Layout Forms
Process Product
Cellular
Fixed position Hybrid
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Process (Job Shop) Layouts
Equipment that perform similar processes aregrouped together
Used when the operations system must handle a wide
variety of products in relatively small volumes (i.e.,
flexibility is necessary)
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Characteristics of Process Layouts
General-purpose equipment is used Changeover is rapid
Material flow is intermittent
Material handling equipment is flexible Operators are highly skilled
. . . more
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Characteristics of Process Layouts
Technical supervision is required Planning, scheduling and controlling functions are
challenging
Production time is relatively long
In-process inventory is relatively high
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Product (Assembly Line) Layouts
Operations are arranged in the sequence required tomake the product
Used when the operations system must handle a
narrow variety of products in relatively high volumes
Operations and personnel are dedicated to producing
one or a small number of products
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Characteristics of Product Layouts
Special-purpose equipment are used Changeover is expensive and lengthy
Material flow approaches continuous
Material handling equipment is fixed Operators need not be as skilled
. . .more
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Characteristics of Product Layouts
Little direct supervision is required Planning, scheduling and controlling functions are
relatively straight-forward
Production time for a unit is relatively short
In-process inventory is relatively low
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Cellular Manufacturing (CM) Layouts
Operations required to produce a particular family(group) of parts are arranged in the sequence required
to make that family
Used when the operations system must handle a
moderate variety of products in moderate volumes
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Characteristics of CM
Relative to Process Layouts
Equipment can be less general-purpose Material handling costs are reduced
Training periods for operators are shortened
In-process inventory is lower Parts can be made faster and shipped more quickly
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Characteristics of CM
Relative to a Product Layout
Equipment can be less special-purpose Changeovers are simplified
Production is easier to automate
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Fixed-Position Layouts
Product remains in a fixed position, and thepersonnel, material and equipment come to it
Used when the product is very bulky, large, heavy or
fragile
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Hybrid Layouts
Actually, most manufacturing facilities use acombination of layout types.
An example of a hybrid layout is where departments
are arranged according to the types of processes but
the products flow through on a product layout.
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New Trends in Manufacturing Layouts
Designed for quality and flexibility Ability to quickly shift to different product models or
to different production rates
Cellular layout within larger process layouts
Automated material handling
U-shaped production lines
. . . more
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New Trends in Manufacturing Layouts
More open work areas with fewer walls, partitions, orother obstacles
Smaller and more compact factory layouts
Less space provided for storage of inventories
throughout the layout
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Process Layouts Product Layouts
Cellular Layouts
Analyzing Manufacturing Facility Layouts
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Designing and Analyzing a Process Layout
Group like processes together into departments orwork centers
Determine where in the building these departments
will be located relative to one another
The objective is to arrange the departments so that
some criterion such as material-handling cost is
minimized
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Approaches to Process Layout Design
Operations sequence analysis Block diagram analysis
Load-distance analysis
Computer analysis
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Operations Sequence Analysis
Inputs required an existing or proposed arrangement of
departments
a projection of the traffic or flow that will take
place between one department and each of the
other departments during some time period - this is
usually displayed as an interdepartmental flow
matrix . . .more
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Operations Sequence Analysis
Departments are represented by nodes (circles) Using the interdepartmental flow information, flows
between adjacent departments are represented by
solid lines. Dashed lines represent traffic between
nonadjacent departments. The projected volumes arewritten above the appropriate lines.
. . . more
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Operations Sequence Analysis
Departments (circles) are moved with the objective ofreducing the amount of nonadjacent flow.
This proceeds until no further improvement can be
found
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Block Diagram Analysis
This approach follows the operations sequenceanalysis and is an effort to make the solution more
realistic
Each department is represented by a square the
relative size of the department
Shapes of the squares are altered to fit into the
boundaries of the building while retaining the same
areas and relative position found in the operationssequence analysis
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Load-Distance Analysis
A way of quantitatively comparing alternativeprocess layouts
Inputs
Alternative block layouts which will provide the
distance between a department and each of the
other departments
For each product, the path it will follow (routing)
and its volume over some time period . . . more
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Load-Distance Analysis
For each alternative process layout, compute the totaldistance a product must travel using its routing
Compute the total distance traveled per time unit for
each product by multiplying its total travel distance
by its volume per time unit
Add the total distance traveled per time unit for each
product
Select the layout with the smallest sum
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Computer Analysis of Process Layouts
There are several computer programs that performanalyses similar to those outlined above
Computerized Relative Allocation of Facilities
Technique (CRAFT) uses material handling cost as
its criterion
. . . more
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Computer Analysis of Process Layouts
Automated Layout Design Program (ALDEP) andComputerized Relative Layout Planning (CORELAP)
use closeness ratings, a relative measure of how
desirable it is for two departments to be close
together, as their criterion
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Designing and Analyzing a Product Layout
Line Balancing
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Designing and Analyzing a Product Layout
Characteristics Inputs
Design Procedure
How Good Is The Layout?
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Line Balancing Problem
Work stations are arranged so that the output of one isan input to the next, i.e., a series connection
Layout design involves assigning one or more of the
tasks required to make a product to work stations
. . . more
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Line Balancing Problem
The objective is to assign tasks to minimize theworkers idle time, therefore idle time costs, and meet
the required production rate for the line
In a perfectly balanced line, all workers would
complete their assigned tasks at the same time(assuming they start their work simultaneously)
This would result in no idle time
. . . more
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Line Balancing Problem
Unfortunately there are a number of conditions thatprevent the achievement of a perfectly balanced line
The estimated times for tasks
The precedence relationships for the tasks
The combinatorial nature of the problem
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Inputs
The production rate required from the product layoutor 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
. . . more
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Inputs
The estimated time to do each task The precedence relationships between the tasks
These relationships are determined by the technical
constraints imposed by the product
These relationships are displayed as a network
known as a precedence diagram
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Design Procedure
1. If not provided, find the cycle time for the line.Remember the cycle time is the reciprocal of the
production rate. Make sure the cycle time is
expressed in the same time units as the estimated task
times.2. Select the line-balancing heuristic that may be used to
help with the assignments. (Two heuristics are
described at the end of this procedure.)
. . . more
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Design Procedure
3. Open a new work station with the full cycle timeremaining.
4. Determine which tasks are feasible, i.e., can be
assigned to this work 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 less than or equalto the remaining cycle time for that work station.
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Design Procedure
5. If there are no feasible tasks, assignments to thatwork station are complete. Go back to step 3 (or stop,
if all tasks have been assigned).
If there is only one feasible task, assign it to the
work station. If there is more than one feasible task,use the heuristic (step 2) to determine which task to
assign. Reduce the work stations remaining cycle
time by the selected tasks time and return to step 4.
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Line-Balancing Heuristics
Heuristic methods, based on simple rules, have beenused to develop very good, not optimal, solutions to
line balancing problems.
Incremental Utilization Heuristic - adds tasks to a
workstation one at a time in the order of taskprecedence until utilization is 100% or is observed to
fall.
Longest-Task-Time Heuristic - adds tasks to aworkstation one at a time in the order of task
precedence, choosing - when a choice must be made -
the task with the longest time.
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How Good Is the Design?
Utilization is one way of objectively determining hownear perfectly balanced an assignment scheme is.
Utilization is the percentage of time that a production
line is working.
Utilization is calculated as:
or
100stations)workofnumber(ActualTime)(Cycle
stask timeallofSumx
x
100onsworkstatiofnumberActual
onsworkstatiofnumberMinimumx
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Designing and Analyzing a Cellular Layout
Fundamental questions: Which parts are going to be produced in a cell?
Which processes are going to be assigned to a cell?
Fundamental Requirements
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Fundamental Requirements
for Parts to be Made in Cells
Demand for the parts must be high enough and stableenough that moderate batch sizes of the parts can be
produced periodically.
Parts must be capable of being grouped into parts
families.
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Design Procedure
1. Form the Parts-Machines Matrix.2. Rearrange the Rows.
Place the machines that produce the same parts in
adjacent rows.
3. Rearrange the Columns.
Place the parts requiring the same machines in
adjacent columns.
4. Using the rearranged parts-machines matrix toidentify cells, the machines for that cell and the parts
that will be produced in that cell.
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Service Facility Layouts
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Characteristics of Services
There may be a diversity of services provided. There are three dimensions to the type of service:
Standard or custom design
Amount of customer contact
Mix of physical goods and intangible services
There are three types of service operations:
Quasi manufacturing
Customer-as-participant
Customer-as-product
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Characteristics of Service Facility Layouts
The encounter between the customer and the servicemust be provided for.
The degree to which customer-related features must
be provided varies with the amount of involvement
and customer contact.
A i S i i i
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Analyzing Service Facility Layouts
For quasi manufacturing services, approaches used todesign and analyze process and product layouts may
be used.
Provide for customer waiting lines.
W U W ld Cl P i
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Wrap-Up: World-Class Practice
Strive for flexibility in layouts Multi-job training of workers
Sophisticated preventive-maintenance programs
Flexible machines
Empowered workers trained in problem solving
Layouts small and compact
Services follow the above practices plus incorporate
customer needs in design
E d f Ch 8
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End of Chapter 8