Chapter 10 and 12

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Facility Layout

(Chapter 10)

Production & Operations Management

INFO 335-71

Week 3

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

⚫ Describe the steps involved in designing a product

layout

⚫ Define the meaning of group technology (cell)

layouts

Types of Layouts

⚫ Four basic layout types:

• Process layouts - Group similar resources together based on similar processes/functions

• Product layouts - Designed to produce a specific product efficiently

• Hybrid layouts - Combine aspects of both process and product layouts

• Fixed-Position layouts - Product is too large to move; e.g. a building

Process vs. Product Layouts

Characteristic differences:

Designing Process Layouts

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

measures (From-to Matrix, REL, SLP)

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

distance model, ALDEP, CRAFT)

Step 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

Load-Distance Model

Warehouse Layout

Trips/block

Designing Product Layouts

⚫ Designing product layouts requires consideration of:

• Sequence of tasks to be performed by each workstation • Logical order • Speed considerations – line balancing

WS1 WS2 WS3 WS4

Work In-

process

Inventory

t t t t

Raw After

WS1

After

WS2

After

WS3

Finished

Product

Designing Product Layouts – cont'd

Step 1: Identify tasks & immediate predecessors

Step 2: Determine output rate

Step 3: Determine cycle time

Step 4: Compute the Theoretical Minimum number

of Stations

Step 5: Assign tasks to workstations

(balance the line)

Step 6: Compute efficiency, idle time &

balance delay

Step 1: Identify Tasks &

Immediate Predecessors

Example 10.4 Vicki's Pizzeria and the Precedence Diagram

Immediate Task Time

Work Element Task Description Predecessor (seconds A Roll dough None 50

B Place on cardboard backing A 5

C Sprinkle cheese B 25

D Spread Sauce C 15

E Add pepperoni D 12

F Add sausage D 10

G Add mushrooms D 15

H Shrinkwrap pizza E,F,G 18

I Pack in box H 15

Total task time 165

Precedence Diagram

bottleneck

Step 2: Determine Output Rate

⚫ Output Rate is the number of units to be produced

over a specific period of time

• Vicki needs to produce 60 pizzas per hour

• Vicki will need to divide the work among a number of people simultaneously at workstations

⚫ The goal is to design a product layout that can

produce the desired number of units with the least

amount of work centers and a balance of workload

hourper pizzas 8.12 sec./unit 165

sec./hr. 3600 output M aximum ==

Minimum

Step 3: Determine Cycle Time

⚫ Determine cycle time calculations

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

• Limited by the bottleneck task (the longest task):

• Minimum cycle time = bottleneck (50 sec.) • Maximum cycle time = sum of the task times (165

sec.)

( ) ( )

sec./unit 60 units/hr 60

sec/min 60x min/hr 60

units/hroutput desired

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

hourper pizzas 72 sec./unit 50

sec./hr. 3600 output Maximum ==

Seconds/hr

60 pizzas per hour

60 pizzas per 3600 seconds

1 pizza every 3600/60 = 60 seconds

Step 4: Theoretical Minimum

Number of Stations

⚫ Computing the theoretical minimum (TM) 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,

itseconds/un 60

itseconds/un 165

timecycle

task times TM ===

 Round it up

Step 5: Assign Tasks to

Workstations ⚫ Assigning tasks to workstations (Balance the Line)

• 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

WS1

WS2

WS3

Step 6: Efficiency and Balance

Delay

⚫ Computing 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%100 sec. 60x stations 3

sec. 165

t (%) Efficiency === 

8.3%91.7%100%delay Balance =−= (15/180)*100

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 • Un-paced has more autonomy; product may be

removed off assembly line

⚫ Number of Product Models produced • Single-model lines – one version of a product • Mixed-model lines – many versions of a product

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

Problem – Facility Layout

•The items listed below are stored in a one-dock warehouse. How should the item areas be allocated to the warehouse layout below (assume all blocks are equal in area)?

Item Trips Area Needed (blocks) A 300 2 B 220 1 C 72 1 D 50 1 E 24 1

Dock

XYZ Company is designing a new product layout. It plans to use this

production line eight hours a day in order to meet a schedule of 50 units

per hour. The task necessary to produce this product are detailed in the

table below,

(a) Draw the precedence Diagram 3pt

(b) What is the required cycle time (seconds) in order to meet the

schedule? 2pts

Schedule? 2pts

(d) Balance the line by assigning tasks to workstations 3pts20

Problem – Product Layout

Task Predecessor Time (seconds)

A - 50

B A 36

C B 26

D - 52

E C,D 70

F C,E 30