facility layout i

7/29/2019 Facility Layout I

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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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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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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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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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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

facility layout i

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