Process layout

© 2007 Pearson Education
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Process Layout
Chapter 8Chapter 8

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

Facility Layout
Defined
Facility layout can be defined as the process by which the
placement of departments, workgroups within
departments, workstations, machines, and stock-
holding points within a facility are determined
This process requires the following inputs:
 Specification of objectives of the system in terms of output
and flexibility
 Estimation of product or service demand on the system
 Processing requirements in terms of number of operations
and amount of flow between departments and work
centers
 Space requirements for the elements in the layout
 Space availability within the facility itself
7A-4

Process Layout: Interdepartmental Flow
 Given
 The flow (number of moves) to and from all
departments
 The cost of moving from one department to
another
 The existing or planned physical layout of
the plant
 Determine
 The “best” locations for each department,
where best means maximizing flow, which
minimizing costs
7A-5

Process Layout: Systematic Layout Planning
 Numerical flow of items between workcenters
 Can be impractical to obtain
 Does not account for the qualitative factors that
may be crucial to the placement decision
 Systematic Layout Planning
 Accounts for the importance of having each
department located next to every other
department
 Is also guided by trial and error
 Switching workcenters then checking the results of
the “closeness” score
7A-6

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 satisfaction
 Level of capital investment
 Requirements for materials handling
 Ease of stockpicking
 Work environment and “atmosphere”
 Ease of equipment maintenance
 Employee and internal customer attitudes
 Amount of flexibility needed
 Customer 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 (process
oriented) Flow Layout
Foundry
Milling
machines
LathesGrinding
Painting Drills
Office
Welding
Forging
A job shop has a flexible-flow layout.

Process-Oriented LayoutProcess-Oriented Layout
 Like machines and equipment areLike machines and equipment are
grouped togethergrouped together
 Flexible and capable of handling aFlexible and capable of handling a
wide variety of products or serviceswide variety of products or services
 Scheduling can be difficult andScheduling can be difficult and
setup, material handling, and laborsetup, material handling, and labor
costs can be highcosts can be high

Process-Oriented LayoutProcess-Oriented Layout
 Arrange work centers so as toArrange work centers so as to
minimize the costs of materialminimize the costs of material
handlinghandling
 Basic cost elements areBasic cost elements are
 Number of loads (or people) movingNumber of loads (or people) moving
between centersbetween centers
 Distance loads (or people) moveDistance loads (or people) move
between centersbetween centers

Office LayoutOffice Layout
 Grouping of workers, their equipment,Grouping of workers, their equipment,
and spaces to provide comfort, safety,and spaces to provide comfort, safety,
and movement of informationand movement of information
 Movement ofMovement of
information is maininformation is main
distinctiondistinction
 Typically in state ofTypically in state of
flux due to frequentflux due to frequent
technologicaltechnological
changeschanges

Example of Systematic Layout Planning:
Importance of Closeness
Value
A
E
I
O
U
X
Closeness
Line
code
Numerical
weights
Absolutely necessary
Especially important
Important
Ordinary closeness OK
Unimportant
Undesirable
16
8
4
2
0
80
7A-14

Relationship ChartRelationship Chart
Figure 9.1Figure 9.1

Fixed-Position LayoutFixed-Position Layout
 Product remains in one placeProduct remains in one place
 Workers and equipment come to siteWorkers and equipment come to site
 Complicating factorsComplicating factors
Limited space at siteLimited space at site
Different materialsDifferent materials
required at differentrequired at different
stages of the projectstages of the project
Volume of materialsVolume of materials
needed is dynamicneeded is dynamic

Line Flow (product
oriented) Layout
Station 1 Station 2 Station 3 Station 4
A production line has a line-flow layout.

McDonald’s AssemblyMcDonald’s Assembly
LineLine
Figure 9.12Figure 9.12

Product-Oriented LayoutProduct-Oriented Layout
1.1. Volume is adequate for high equipment utilizationVolume is adequate for high equipment utilization
2.2. Product demand is stable enough to justify highProduct demand is stable enough to justify high
investment in specialized equipmentinvestment in specialized equipment
3.3. Product is standardized or approaching a phase ofProduct is standardized or approaching a phase of
life cycle that justifies investmentlife cycle that justifies investment
4.4. Supplies of raw materials and components areSupplies of raw materials and components are
adequate and of uniform qualityadequate and of uniform quality
Organized around products or families of similarOrganized around products or families of similar
high-volume, low-variety productshigh-volume, low-variety products

Product-Oriented LayoutsProduct-Oriented Layouts
1.1. Low variable cost per unitLow variable cost per unit
2.2. Low material handling costsLow material handling costs
3.3. Reduced work-in-process inventoriesReduced work-in-process inventories
4.4. Easier training and supervisionEasier training and supervision
5.5. Rapid throughputRapid throughput
AdvantagesAdvantages
1.1. High volume is requiredHigh volume is required
2.2. Work stoppage at any point ties up the wholeWork stoppage at any point ties up the whole
operationoperation
3.3. Lack of flexibility in product or production ratesLack of flexibility in product or production rates
DisadvantagesDisadvantages

Comparison of Product vs.
Product Layouts
Process Layouts Product Layouts
Products: 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 faster
Rates:
Handling costs: high low
Space requirements: higher lower

Assembly Line
Balancing
 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.

Assembly Line
Balancing
 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
Balancing
1. 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
D
P
C ==
cycle_time
task_times
C
T
N
∑
==t

Assembly Line
Balancing
5. 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
T
E −= a
a

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

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./unit60
units/hr60
sec/min60xmin/hr60
units/hroutputdesired
sec./daytimeavailable
)(sec./unittimeCycle ===
hourperpizzasorunits/hr,72
sec./unit50
sec./hr.3600
timetaskbottleneck
timeavailable
outputMaximum ===

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
( )
stations3or2.75,
nsec/statio60
seconds165
timecycle
timestask
TM ===
∑

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%100
sec.60xstations3
sec.165
NC
t
(%)Efficiency ===
∑
8.3%91.7%100%delayBalance =−=

Line Balancing
Example 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 information in the previous slide,
answer the following questions:
1.Construct a Precedence diagram
2.If the company would like to product 60 units
per hour determine cycle time:
5.Determine required workstations (theoretical
minimum)
6.Assign tasks to workstations
7.Calculate line efficiency:

© 2007 Pearson Education© 2007 Pearson Education
Line Balancing
Green Grass, Inc.Green Grass, Inc.
66
E
2020
H
1818
I
4040
D
3030
B
2525
F
5050
C4040
A
1515
G
AA Bolt leg frame to hopperBolt leg frame to hopper 4040 NoneNone
BB Insert impeller shaftInsert impeller shaft 3030 AA
CC Attach axleAttach axle 5050 AA
DD Attach agitatorAttach agitator 4040 BB
EE Attach drive wheelAttach drive wheel 66 BB
FF Attach free wheelAttach free wheel 2525 CC
GG Mount lower postMount lower post 1515 CC
HH Attach controlsAttach controls 2020 D, ED, E
II Mount nameplateMount nameplate 1818 F, GF, G
TotalTotal 244244
WorkWork TimeTime ImmediateImmediate
ElementElement DescriptionDescription (sec)(sec) Predecessor(s)Predecessor(s)

Application 8.3

Using the information in the previous slide, answer the
following questions:
1.Construct a Precedence diagram
2.If the company would like to product 60 units per
hour determine cycle time:
5.Determine required workstations (theoretical
minimum)
6.Assign tasks to workstations
7.Calculate line efficiency:

Solved Problem 2

Solved Problem 2
Precedence Diagram
2020
E
145145
H
130130
I
2525
D
8080
B
1515
F
5050
C
4040
A
120120
G
115115
J

Solved Problem 2
Line Balancing Process

Solved Problem 2
Line Balancing Solution
2020
E
145145
H
130130
I
2525
D
8080
B
1515
F
5050
C
4040
A
120120
G
115115
JS1
S4
S2
S5
S3

Process layout

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