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Chapter 10 – Facility Layout

Operations Managementby

R. Dan Reid & Nada R. Sanders4th Edition © Wiley 2010

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Learning Objectives Define layout planning and explain its

importance Identify and describe different types

of layouts Compare process layouts & product

layouts Describe the steps involved in

designing a process layout

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Learning Objectives – con’t

Describe the steps involved in designing a product layout

Explain the advantages of hybrid layouts

Define the meaning of group technology (cell) layouts

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What Is Layout Planning?

Layout planning is deciding the best physical arrangement of all resources within a facility

Facility resource arrangement can significantly affect productivity

Two broad categories of operations: Intermittent processing systems – low volume of many

different products Continuous processing systems – high volume of a few

standardized products

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Types of Layouts

Four basic layout types consisting of: Process layouts - Group similar resources

together Product layouts - Designed to produce a

specific product efficiently Hybrid layouts - Combine aspects of both

process and product layouts Fixed-Position layouts - Product is two large

to move; e.g. a building

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Process Layouts Process layout unique characteristics

include:

Resources used are general purpose Facilities are less capital intensive Facilities are more labor intensive Resources have greater flexibility Processing rates are slower Material handling costs are higher

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Process Layouts – con’t

Scheduling resources & work flow is more complex

Space requirements are higher

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Product Layouts

Product layout unique characteristics are: Resources are specialized Facilities are capital intensive Processing rates are faster Material handling costs are lower Space requirements for inventory storage

are lower Flexibility is low relative to the market

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Process vs. Product Layouts

Here are the characteristic differences between a process and product layout.

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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

Examples: Group technology & manufacturing cells Grocery stores

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Fixed-Position Layout

Used when product is large Product is difficult or impossible to

move, i.e. very large or fixed All resources must be brought to the

site Scheduling of crews and resources is a

challenge

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Designing Process Layouts

Step 1: Gather information:Space needed, space available, identify closeness

measures

Step 2: Develop alternative block plans:Using trial-and-error or decision support tools

Step 3: Develop a detailed layout:Consider exact sizes/shapes of departments and

work centers including aisles and stairwaysTools like drawings, 3-D models, and CAD

software are available to facilitate this process

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Special Cases of Process Layouts

A number of unique process layouts require special attention. We will look at two of these:

Warehouse layouts Office Layouts

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Warehouse Layouts

Warehouse Layout Considerations: Primary decision is where to locate each

department relative to the dock Departments can be organized to minimize

“ld” totals Departments of unequal size require

modification of the typical ld calculations to include a calculation of the “ratio of trips to area needed”

The usage of “Crossdocking” modifies the traditional warehouse layouts; more docks, less storage space, and less order picking

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Office Layouts

Office Layout Considerations: Almost half of US workforce works in an office

environment Human interaction and communication are the

primary factors in designing office layouts Layouts need to account for physical environment

and psychological needs of the organization One key layout trade-off is between proximity and

privacy Open concept offices promote understanding &

trust Flexible layouts incorporating “office landscaping”

help to solve the privacy issue in open office environments

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Designing Product Layouts

Designing product layouts requires consideration of: Sequence of tasks to be performed by

each workstation Logical order Speed considerations – line balancing

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Designing Product Layouts – con’t

Step 1: Identify tasks & immediate predecessorsStep 2: Determine output rateStep 3: Determine cycle timeStep 4: Compute the Theoretical Minimum number

of StationsStep 5: Assign tasks to workstations (balance the line)Step 6: Compute efficiency, idle time & balance

delay

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Step 1: Identify Tasks & Immediate PredecessorsExample 10.4 Vicki's Pizzeria and the Precedence Diagram

Immediate Task TimeWork Element Task Description Predecessor (seconds

A Roll dough None 50B Place on cardboard backing A 5C Sprinkle cheese B 25D Spread Sauce C 15E Add pepperoni D 12F Add sausage D 10G Add mushrooms D 15H Shrinkwrap pizza E,F,G 18I Pack in box H 15

Total task time 165

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Layout Calculations Step 2: Determine output rate

Vicki needs to produce 60 pizzas per hour Step 3: Determine cycle time

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

Limited by the bottleneck task (the longest task in a process):

sec./unit 60

units/hr 60

sec/min 60x min/hr 60

units/hroutput desired

sec./day time available)(sec./unit time Cycle

hourper pizzasor units/hr, 72sec./unit 50

sec./hr. 3600

time task bottleneck

time availableoutput Maximum

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Layout Calculations con’t Step 4: Compute the theoretical

minimum number of stations 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

stations 3or 2.75,

nsec/statio 60

seconds 165

time cycle

times taskTM

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Layout Calculations con’t Step 5: Assign tasks to workstations

Start at the first station & choose the longest eligible task following precedence relationships

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

When no additional tasks can be added within the desired cycle time, begin assigning tasks to the next workstation until finished

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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Last Layout Calculation Step 6: Compute efficiency and balance

delay Efficiency (%) is the ratio of total

productive time divided by total time

Balance delay (%) is the amount by which the line falls short of 100%

91.7%100sec. 60x stations 3

sec. 165

NC

t (%) Efficiency

8.3%91.7%100%delay Balance

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Other Product Layout Considerations

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

visibility, impact location of loading & unloading

Paced versus Un-paced lines Paced lines use an automatically enforced cycle

time

Number of Product Models produced Single Mixed-model lines

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Group Technology (CELL) Layouts One of the most popular hybrid layouts uses

Group Technology (GT) and a cellular layout GT has the advantage of bringing the efficiencies

of a product layout to a process layout environment

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Process Flows before the Use of GT Cells

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Process Flows after the Use of GT Cells

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Facility Layout Across the Organization

Layout planning is organizationally important for an efficient operations Marketing is affected by layout

especially when clients come to the site Human resources is affected as layout

impacts people Finance is involved as layout changes

can be costly endeavors

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Facility Layout within OM: How it all fits together

Layout decisions are directly related to issues of product design and process selection (Ch 3).

Job design, as process layouts tend to require greater worker skills than do product layouts (Ch 11).

Degree of automation, as product layouts tend to be more capital intensive and use more automation compared to process layouts (Ch 3).

Layout decisions are also affected by implementation of just-in-time (JIT) systems, which dictate a line flow and the use of group technology (GT) cells (Ch 7).

As layout decisions specify the flow of goods through the facility, they impact all other aspects of operations management.

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Chapter 10 Highlights Layout planning is deciding on the best physical

arrangement of all resources that consumes space within a facility. Proper layout planning is highly important for the efficient running of a business. Otherwise, there can be much wasted time and energy, as well as confusion.

There are four basic types of layouts: process, product, hybrid, and fixed position. Process layouts group resources based on similar processes. Product layouts arrange resources in straight-line fashion. Hybrid layouts combine elements of both process and product layouts. Fixed-position layouts occur when the product is larger and cannot be moved.

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Chapter 10 Highlights – con’t

Process layouts provide much flexibility and allow for the production of many products with differing characteristics. Product layouts, on the other hand, provide greater efficiency when producing one type of product.

The steps for designing process layouts are (1) gather information about space needs, space availability, and closeness requirements of departments; (2) developing a block plan or schematic of the layout; and (3) developing a detailed layout.

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Chapter 10 Highlights – con’t

The steps for designing an product layout are (1) identify tasks that need to be performed and their immediate predecessors; (2) determine output rate; (3) determine cycle time; (4) computing the theoretical minimum number of work stations, (5) assigning tasks to workstations; and (6) computing efficiency and balance delay.

Hybrids layouts have advantages over other layout types because they combine elements of both process and product layouts to increase efficiency.

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Chapter 10 Highlights – con’t

An example of hybrid layouts is group technology or cell layouts. Group technology is the process of crating groupings of products based on similar processing requirements. Cells are created for each grouping of products, resulting in a more orderly flow of products through the facility.

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