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Chapter 8

Process Layout 1

© 2007 Pearson Education

D D

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Process Layout

Chapter 8Chapter 8


How Process Layout fits the Operations Management

Philosophy

Operations As a Competitive Weapon

Operations StrategyProject Management Process Strategy

Process AnalysisProcess Performance and Quality

Constraint ManagementProcess Layout

Lean Systems

Supply Chain StrategyLocation

Inventory ManagementForecasting

Sales and Operations PlanningResource Planning

Scheduling


Layout Planning

Layout planning is planning that involves decisions about the physical arrangement of economic activity centers needed by a facility’s various processes.

Layout plans translate the broader decisions about the competitive priorities, process strategy, quality, and capacity of its processes into actual physical arrangements.

Economic activity center: Anything that consumes space -- a person or a group of people, a customer reception area, a teller window, a machine, a workstation, a department, an aisle, or a storage room.


Before a manager can make decisions regarding physical arrangement, four questions must be addressed.

1. What centers should the layout include?2. How much space and capacity does

each center need?3. How should each center’s space be

configured?4. Where should each center be located?

Layout Planning Questions


Location Dimensions

The location of a center has two dimensions:

1. Relative location: The placement of a center relative to other centers.

2. Absolute location: The particular space that the center occupies within the facility.


Absolute Locations vs. Relative Locations

Original layout

Frozen foods

Dry groceries

Bread Vegetables

Meats

Frozen foods

Dry groceries

BreadVegetables

Meats

Revised layout

Four of the absolute locations have changed but not the relative locations.

Chapter 8

Process Layout 2


Strategic Issues

Layout choices can help communicate an organization’s product plans and competitive priorities.Altering a layout can affect an organization and how well it meets its competitive priorities in the following ways:

1. Increasing customer satisfaction and sales at a retail store.2. Facilitating the flow of materials and information.3. Increasing the efficient utilization of labor and equipment.4. Reducing hazards to workers.5. Improving employee morale.6. Improving communication.


Performance Criteria

Customer satisfactionLevel of capital investmentRequirements for materials handlingEase of stockpickingWork environment and “atmosphere”Ease of equipment maintenanceEmployee and internal customer attitudesAmount of flexibility neededCustomer convenience and levels of sales


Types of Layouts

Flexible-flow layout: A layout that organizes resources (employees) and equipment by function rather than by service or product.Line-flow layout: A layout in which workstations or departments are arranged in a linear path.Hybrid layout: An arrangement in which some portions of the facility have a flexible-flow and others have a line-flow layout.Fixed-position layout: An arrangement in which service or manufacturing site is fixed in place; employees along with their equipment, come to the site to do their work.


A Flexible Flow Layout

FoundryMilling

machines

LathesGrinding

Painting Drills

Office

Welding

Forging

A job shop has a flexible-flow layout.


Line Flow Layout

Station 1 Station 2 Station 3 Station 4

A production line has a line-flow layout.


Creating Hybrid Layouts

Layout flexibility is the property of a facility to remain desirable after significant changes occur or to be easily and inexpensively adopted in response to changes.A One-worker, multiple-machines (OWMM) cell is a one-person cell in which a worker operates several different machines simultaneously to achieve a line flow.A Cell is two or more dissimilar workstations located close together through which a limited number of parts or models are processed with line flows.

Chapter 8

Process Layout 3


Machine 1

Machine 2

Machine 3

Machine 4Machine

5

Materials in

Finished goods out

One Worker, One Worker, Multiple Machines Multiple Machines


Group Technology (GT)

Group Technology (GT) is an option for achieving line-flow layouts with low-volume processes; this technique creates cells not limited to just one worker and has a unique way of selecting work to be done by the cell.

The GT method groups parts or products with similar characteristics into families and sets aside groups of machines for their production.


Before Group Technology

Drilling

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Grinding

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Milling

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Assembly

A A

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Lathing

Receiving and shipping

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Jumbled flows in a job shop without GT cellsJumbled flows in a job shop without GT cells


Applied Group TechnologyLine flows in a job shop with three GT cells Line flows in a job shop with three GT cells

Cell 3

L M G G

Cell 1 Cell 2

Assembly area

A A

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L MShipping

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Receiving

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Designing Flexible-Flow Layouts

Step 1: Gather informationSpace requirements by centerAvailable spaceCloseness factors: which centers need to be located close to one another.

Closeness matrix: A table that gives a measure of the relative importance of each pair of centers being located close together.Step 2: Develop a Block plan: A plan that allocates space and indicates placement of each department.Step 3: Design a detailed layout.


Gather Information

100'

150'

3 6 4

1 2 5

Current Block Plan

Department Area Needed (ft2)1. Administration 3,5002. Social services 2,6003. Institutions 2,4004. Accounting 1,6005. Education 1,5006. Internal audit 3,400

Total 15,000

Space Requirements

Example 8.1 Office of Budget Management

Chapter 8

Process Layout 4


100'

150'

3 6 4

1 2 5 Closeness Matrix

Trips between Departments

Department 1 2 3 4 5 61. Administration —2. Social services —3. Institutions —4. Accounting —5. Education —6. Internal audit —

3 6 5 6 108 1 1

3 92

1

Departments 1 and 6 have the most interaction.Departments 3 and 5 have the next highest.Departments 2 and 3 have next priority.

Example 8.1 Office of Budget Management


100'

150'

100'

150'

3 6 4

1 2 5 Proposed Block Plan

First put departments 1 and 6 close together

1

6

Next put departments 3 and 5 close together

5

3

Then put departments 2 and 3 close together

2

4


Weighted-distance method: A mathematical model used to evaluate flexible-flow layouts based on proximity factors.

Euclidean distance is the straight-line distance, or shortest possible path, between two points.

Rectilinear distance: The distance between two points with a series of 90 degree turns, as along city blocks.

Applying the Weighted- Distance Method


Distance Measures

Rectilinear DistanceRectilinear Distance

ddABAB = |= |xxAA –– xxBB| + || + |yyAA –– yyBB||

Euclidian DistanceEuclidian Distance

ddABAB = (= (xxAA –– xxBB))22 + (+ (yyAA –– yyBB))22


Application 8.1

Rectilinear DistanceRectilinear Distance

ddABAB = |20= |20 –– 80| + |10 80| + |10 –– 60| = 11060| = 110

Euclidian DistanceEuclidian Distance

ddABAB = (20= (20 –– 80)80)22 + (10 + (10 –– 60)60)22

= 78.1= 78.1

What is the distance between (20,10) and (80,60)?

© 2007 Pearson Education© 2007 Pearson Education

Example 8.2 Load Distance AnalysisCurrent Plan Proposed Plan

Dept Closeness Distance DistancePair Factor, w d wd Score d wd Score1,2 3 1 3 2 61,3 6 1 6 3 181,4 5 3 15 1 51,5 6 2 12 2 121,6 10 2 20 1 102,3 8 2 16 1 82,4 1 2 2 1 12,5 1 1 1 2 23,4 3 2 6 2 63,5 9 3 27 1 94,5 2 1 2 1 25,6 1 2 2 3 3

ld =112 ld = 82

Calculating the WD Score

Chapter 8

Process Layout 5


Excel Solver evaluation of solution

First Proposed Plan


Excel Solver improved solution

Second Proposed Plan


Application 8.2


Application 8.2


Application 8.2


Other Decision Support Tools

Automated layout design program (ALDEP): A computer software package that constructs a good layout from scratch, adding one department at a time.Computerized relative allocation of facilities technique (CRAFT): A heuristic method that begins with the closeness matrix and an initial block layout, and makes a series of paired exchanges of departments to find a better block plan.

Chapter 8

Process Layout 6


Warehouse LayoutsOut-and-back Pattern

The most basic warehouse layout is the out-and-back pattern. The numbers indicate storage areas for same or similar items.

Dock Aisle

Storage area

Storage area

3 5 5 6 4 2 7

1 5 5 4 4 2 7


Warehouse LayoutsZone System

Click to add titleZones Zones Control

station Shipping doors

Tractor trailer

Tractor trailer

OverflowFeeder lines

Feeder lines


Office Layouts

Most formal procedures for designing office layouts try to maximize the proximity of workers whose jobs require frequent interaction.Privacy is another key factor in office design.Four common office layouts:1. Traditional layouts2. Office landscaping (cubicles/movable partitions) 3. Activity settings4. Electronic cottages (Telecommuting)


Designing Line-Flow Layouts

Line balancing is the assignment of work to stations in a line so as to achieve the desired output rate with the smallest number of workstations.Work elements are the smallest units of work that can be performed independently.Immediate predecessors are work elements that must be done before the next element can begin.Precedence diagram allows one to visualize immediate predecessors better; work elements are denoted by circles, with the time required to perform the work shown below each circle.


Line BalancingExample 8.3Example 8.3

Green Grass, Inc., a manufacturer of lawn & garden equipment, is designing an assembly line to produce a new fertilizer spreader, the Big Broadcaster. Using the following information, construct a precedence diagram for the Big Broadcaster.


Line BalancingGreen Grass, Inc.Green Grass, Inc.

66E

2020H

1818I

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3030B

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1515G

AA Bolt leg frame to hopperBolt leg frame to hopper 4040 NoneNoneBB Insert impeller shaftInsert impeller shaft 3030 AACC Attach axleAttach axle 5050 AADD Attach agitatorAttach agitator 4040 BBEE Attach drive wheelAttach drive wheel 66 BBFF Attach free wheelAttach free wheel 2525 CCGG Mount lower postMount lower post 1515 CCHH Attach controlsAttach controls 2020 D, ED, EII Mount nameplateMount nameplate 1818 F, GF, G

TotalTotal 244244

WorkWork TimeTime ImmediateImmediateElementElement DescriptionDescription (sec)(sec) Predecessor(s)Predecessor(s)

Chapter 8

Process Layout 7


Desired Output and Cycle Time

Desired output rate, r must be matched to the staffing or production plan.

Cycle time, c is the maximum time allowed for work on a unit at each station: 1

rc =


Theoretical Minimum

Theoretical minimum (TM ) is a benchmark or goal for the smallest number of stations possible, where total time required to assemble each unit (the sum of all work-element standard times) is divided by the cycle time. It must be rounded up

Idle time is the total unproductive time for all stations in the assembly of each unit.Efficiency (%) is the ratio of productive time to total time.Balance Delay is the amount by which efficiency falls short of 100%.


Output Rate and Cycle TimeExample 8.4

Green Grass, Inc.Desired output rate, r = 2400/week

Plant operates 40 hours/weekr = 2400/40 = 60 units/hour

Cycle time, c = 1/60

= 1 minute/unit

= 60 seconds/unit

1r


Calculations for Example 8.4 continued

Theoretical minimum (TM ) - sum of all work-element standard times divided by the cycle time.

TM = 244 seconds/60 seconds = 4.067 It must be rounded up to 5 stations

Cycle time: c = 1/60 = 1 minute/unit = 60 seconds/unit

Efficiency (%) - ratio of productive time to total time.

Efficiency = [244/5(60)]100 = 81.3%

Balance Delay - amount by which efficiency falls short of 100%.

(100 − 81.3) = 18.7%


S1

S2S3

S5S4 66

E2020H

1818I

4040D

3030B

2525F

5050C4040

A

1515G

Green Grass, Inc. Green Grass, Inc. Line Balancing SolutionLine Balancing Solution

cc = 60 seconds/unit= 60 seconds/unitTM = 5 stationsTM = 5 stationsEfficiency = 81.3%Efficiency = 81.3%

The goal is to cluster the work elements into 5 workstations so that the number of work-stations is minimized, and the cycle time of 60 seconds is not violated. Here we use the trial-and-error method to find a solution, although commercial software packages are also available.


Application 8.3

Chapter 8

Process Layout 8


Application 8.3


Application 8.3


Application 8.4Finding a Solution


Other Considerations

In addition to balancing a line, managers must also consider four other options:

1. Pacing: The movement of product from one station to the next as soon as the cycle time has elapsed.

2. Behavioral factors of workers.3. Number of models produced: A mixed-model line

produces several items belonging to the same family.

4. Cycle times depend on the desired output rate, and efficiency varies considerably with the cycle time selected. Thus exploring a range of cycle times makes sense.

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