Chapter 10 – Facility Layout

Operations Managementby

R. Dan Reid & Nada R. Sanders3rd Edition © Wiley 2007

Learning Objectives Define layout planning and its importance Identify and describe different types of

layouts Compare process layouts & product

layouts Describe the steps involved in designing

both process and product layouts Explain the advantages of hybrid layouts Define the meaning of group technology

& its importance to cellular layouts

What Is Layout Planning Layout planning is determining the best physical

arrangement of 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

Facility Layout Fixed Position

Product is too large to move; e.g.: a building

Process Group similar resources together

Product Designed to produce a specific product efficiently

Hybrid: combines aspects of both process and product layouts

Cellular Modular

Fixed Position Layout The position of a product or customer

is fixed; and materials, equipment, workers, and other resources are transported to and from the product or customer.

Usually used because product movement is difficult (ship building) or for convenience (on-site repair).

This is often managed through Project Management (Chapter 16).

Process Layout Similar processes/functions are

grouped together (job shop). Volume of parts/services does not warrant product or cellular layout.

Primary advantages--flexibility, utilization of machinery/equipment.

Disadvantages--greater handling of materials/customers, more complex scheduling, WIP/waiting lines, departmental boundaries

Traditional Process Layout

Process Layouts General purpose & flexible resources Lower capital intensity & automation Higher labor intensity Resources have greater flexibility Processing rates are slower Material handling costs are higher Scheduling resources & work flow is more

complex Space requirements are higher

Designing Process Layouts Step 1: Gather information:

Space needed, space available, importance of proximity between various units

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

Step 3: Develop a detailed layout Consider exact sizes and 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

Comparing Alternatives Load-distance measures

Load: # of trips, weight moved, $-value moved Distance: rectilinear distance (using north-

south & east-west movements) REL charts:

Management opinion on strength of relationships

Software tools: CRAFT: computerized relative allocation of

facilities technique ALDEP: automated layout design program

Process Layout Example

Process Layout Steps Step 1: Gather information like space needed, from-to

matrix, and REL Chart for Recovery First Sports Medicine Clinic (total space 3750 sq. ft.)

ARadiology

400 sq. ft.

BLaboratory

300 sq. ft.

CLobby & Waiting

300 sq. ft.

DExamining

Rooms800 sq. ft.

ESurgery & Recovery900 sq. ft.

FPhysical Therapy

1050 sq. ft.

Step 1: Gather Information

(continued)

Step 2: Develop a Block Layout Use trial and error with from-to and

REL Charts as a guide Use computer software like ALDEP or

CRAFT

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” (see Ch.4) modifies the traditional warehouse layouts; more docks, less storage space, and less order picking

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

Product Layout Processes/work stations arranged in

sequence of activities required to produce the product/service (Assembly Line). Use for high volume, standardized products

and services WIP and handling of materials/customers is

minimized Equipment is specialized, capital intensive Output is dependent on the slowest work

station The “line” must be balanced for

effectiveness.

Product Layouts Specialized equipment High capital intensity & wide use of

automation Processing rates are faster Material handling costs are lower Less space required for inventories Less volume or design flexibility

Product Layout

Product A

Product B

Product C

Step 1

Step 1

Step 1

Step 2

Step 2

Step 2

Step 3

Step 3

Step 3

Step 4

Step 4

Step 4

7-14

Designing Product Layouts Step 1: Identify tasks & immediate predecessors Step 2: Determine the desired output rate Step 3: Calculate the cycle time Step 4: Compute the theoretical minimum number of workstations Step 5: Assign tasks to workstations (balance the line) Step 6: Compute efficiency, idle time & balance delay

Assembly Line Balancing1. Precedence diagram: circles=tasks, arrows

show the required sequence.2. Determine cycle time:

3. Determine required workstations (theoretical minimum)

4. Set rules for assigning tasks (number of following tasks, longest task time)

unitput)/time_demand(out/time_unitproduction

DP

C

cycle_timetask_times

CT

N

t

Assembly Line Balancing5. Assign tasks to first workstation,

using rules and staying within cycle time. Repeat for following workstations until all tasks are assigned.

6. Evaluate line efficiency:

7. Rebalance if efficiency is not satisfactory.

kstationsactual_worN;CN

TE a

a

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

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

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

1

2

3

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

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 products produced

Single Mixed-model lines

Comparison of Product vs. Product Layouts

Process Layouts Product LayoutsProducts: large #, different small # efficiently

Resources: general purpose specialized

Facilities: more labor intensive more capital intensive

Flexibility: greater relative to market lower relative to market

Processing slower fasterRates:

Handling costs: high low

Space requirements: higher lower

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

Hybrid Layouts Cellular Layout

Cross between product/process layout group a number of machines into a cell

to produce a family of parts requiring similar processing (group technology).

Often arranged into U- or C-shaped line flows

Modular Layout achieves layout flexibility so that layouts

can be changed, expanded, or reduced without much difficulty.

Designing Hybrid 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

Process Flows before the Use of GT Cells

Process Flows after the Use of GT Cells

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

Chapter 10 Highlights Layout planning is deciding on the best

physical arrangement of resources. There are four basic types of layouts:

process, product, hybrid, and fixed position. Process layouts provide flexibility to make a

variety of different products. Product layouts provide greater efficiency for one product.

The steps for designing process layouts are: gather space and closeness information, develop a block plan, and develop a detailed layout.

Chapter 10 Highlights (continued)

The steps for designing an product layout are: identify tasks and predecessors, determine output rate, determine cycle time, computing the theoretical minimum number of work stations, assigning tasks to workstations, and computing efficiency and balance delay.

Hybrids layouts combine elements from both types of layouts to increase efficiency.

Hybrid layouts combine GT analysis with cellular layout concepts .

Chapter 10 Homework Hints

10.8: Assign sites based on number of trips (refer to Example 10.2). There is no strategy regarding which side of the aisle to assign—just nearness to the dock.

10.16: Follow the steps. This is a product layout (assembly line balancing). The book has an example on pages 360-366, which is also on the slides covered in class.

Sample Problem—10.7

dock aisle

Department

Category Trips to/from

dock

1 Sports t-shirts 50

2 Men’s t-shirts 63

3 Women’s t-shirts 35

4 Children’s t-shirts 55

5 Fashion t-shirts 48

6 Undershirts 60

Sample Problem –10.15

Draw precedence diagram Determine cycle time—demand = 50 units/hr Theoretical minimum no. of work stations Assign tasks to workstations using cycle time Efficiency and balance delay of line? Bottleneck? Maximum output?

Task Imm. predecessor Task time (sec)A None 55

B A 30

C A 22

D B 35

E B, C 50

F C 15

G F 5

H G 10

TOTAL 222