Facility Layout

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FACILITY LAYOUT

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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

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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

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 – continued

-Scheduling resources & work flow is more complex

-Space requirements are higher

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Product LayoutsProduct 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.

Process Layouts Product Layouts

Able to produce a large number of different products

Able to produce a small number of products efficiently

Resources used are general purpose Resources used are specialized

Facilities are more labor intensive Facilities are more capital intensive

Greater flexibility relative to the market Low flexibility relative to the market

Slower processing rates Faster processing rates

High material handling costs Lower material handling costs

Higher space requirements Lower space requirements

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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

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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

measuresStep 2: Develop alternative block plans:

Using trial-and-error or decision support toolsStep 3: Develop a detailed layout:

Consider exact sizes/shapes of departments and work centers including aisles and stairways

Tools 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:1. Primary decision is where to locate

each department relative to the dock2. Departments can be organized to

minimize “ld” totals3. Departments of unequal size require

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

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

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Office LayoutsOffice Layout Considerations

– 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 – continued

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 Predecessors

Example 10.4 Vicki's Pizzeria and the Precedence DiagramImmediate Task Time

Work Element Task Description Predecessor (secondsA 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

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-continued

• 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- Continued• 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

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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. 60 x stations 3

sec. 165

NC

t (%) Efficiency

8.3%91.7%100%delay Balance 20

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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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

Job design, as process layouts tend to require greater worker skills than do product layouts

Degree of automation, as product layouts tend to be more capital intensive and use more automation compared to process layouts

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.

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

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