chapter9 (1) operations

7/28/2019 chapter9 (1) operations

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9-1

Operations

Management

Layout StrategyChapter 9


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Outline

Strategic Importance of Layout Decisions.

Fixed-Position Layout.

Office Layout. Process-Oriented Layout (Flow graphs).

Retail Layout.

Warehouse Layout.

Product-Oriented Layout (Assembly line balancing).


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What is Facility Layout

Location or arrangement of everythingwithin & around buildings.

Objectives are to maximize:

Utilization of space, equipment, & people.

Efficient flow of information, material, & people.

Employee morale & safety.

Trend is towards flexible and dynamic layouts.


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Facility Layout

Helps achieve competitive advantage:

Better, faster, cheaper.

Determines productivity, cost, quality,flexibility, image, etc.

May involve a blend of strategies.


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Six Layout Strategies

1. Fixed-position layout.

For large unique projects such as ships and buildings.

2. Office layout. Positions workers, equipment, and spaces/offices to

provide for movement of information and material.

3. Process-oriented layout. For low-volume, high-variety production.


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Six Layout Strategies - continued

4. Retail/service layout.

Arranges facility and allocates shelf space in light ofcustomer behavior.

5. Warehouse layout.

Addresses trade-offs between space utilization andmaterial handling.

6. Product-oriented layout.

For repetitive or continuous production.


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Layout Strategies

Project

(fixed-position)

Job Shop

(Process-oriented) Office

Examples

Problem

Ingal ShipBuilding

Pittsburgh Airport

ShouldiceHospital

Olive Garden

AllstateInsurance

Microsoft

Move materialto limited

storage areasat the site.

Manage variedmaterial flow for

each product.

Locate workersrequiring contact

close to eachother.


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Layout Strategies

RetailWarehouse

(storage)

Repetitive/Continuous

(Product-oriented)

Examples

Problem

Krogers

Supermarket

Famous-Barr

Federal-MogulsWarehouse

The Gaps

distribution center

Sonys TVAssembly Line

DodgeCaravans

Exposecustomer tohigh-margin

items.

Balance cost forstorage and

materialhandling.

Equalize thetask time at

eachworkstation.


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Requirements for a Good Layout

Understand capacity and space requirements.

Understand information flows.

Understand cost of people and product flows.

Select appropriate material handling equipment.

Consider environment and aesthetics.Consider safety and regulations.


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Constraints on Layout Objectives

Product/service design.

Volume of business.

Process equipment & capacity.

Quality of work life.

Building and site.


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1. Fixed-Position Layout

Project is stationary.

Special purpose: Construction, shipbuilding, etc.

Workers and equipment come to site.Complicating factors.

Limited space at site.

Changing material needs.

Unique projects.


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2. Office Layout

Positions people, equipment, & offices. Usually for maximum information flow.

Also can consider material flow.

Arranged by process or product.

Example: Payroll dept. is by process.

Different cultures have differentexpectations for space.

Relationship (or proximity) chart used.


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Relationship (Proximity) Chart

Uses 6 levels to express desired proximity.

A = Absolutely necessaryE = Especially important

I = Important

O= Ordinary importanceU = Unimportant

X = Not desirable


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1 PresidentO

2 Costing U

E A3 Engineering I

U4 Presidents Secretary

5 Photocopiers

UE

A

X


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1 PresidentO

2 Costing UE A

3 Engineering IU

4 Presidents Secretary

5 Photocopiers

UE

A

X

1

4

3

2

5A

A

E

E

I

X

Can determine layoutusing proximity diagram


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Office Layout

1 President O2 Costing U

E A3 Engineering I

U4 Presidents Secretary

5 Photocopiers

UE

A

X

1

4

3

2

5A

A

E

E

I

X

Locate 5 offices in a rectangular

space.Offices 2-5 are to be same size.

Office 1 (Presidents) is twice as

large.


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Office Layout

Costing

(3)

Photocopiers(5)

PresidentsSecretary

(4)

(2)

President(1)

Engineering

Corridor


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3. Process-Oriented Layout

Place departments with large flows ofmaterial or people close together.

Similar processes and equipment arelocated in close proximity.

For example, all x-ray machines in same area.

Used with process-focused processes.

Low volume, high variety.


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Emergency Room Layout

E.R. beds Pharmacy Billing/exit

E.R.Triage

room

Patient B - erratic

pacemaker

Patient A -broken leg

Hallway


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Process-Oriented Layout Advantages

Flexibility.

Allows wide variety of products.

Low fixed costs for generalpurpose equipment.

Breakdown of one machine or

worker does not stopprocessing.

Process Oriented Layout


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Process-Oriented LayoutDisadvantages

Scheduling is difficult.

High variable cost.

High work-in-processinventory and waiting.

High labor skills required.

Developing a Process Oriented


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Developing a Process-OrientedLayout by Hand

Goal: Minimize cost of moving between departments.

1 Construct a from-to matrix.

2 Determine space requirements for each department.

3 Develop an initial layout and try to place departmentswith large flows close together.

4 Determine the cost of this initial layout.

5 Improve the initial layout (by hand or moresophisticated means).

6 Consider factors in addition to transportation cost.


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Cost of Process-Oriented Layout

jiij

C

jiij

X

i,j

n

ijC

ijX

n

i

n

j

departmentanddepartmentbetweenloadamovetocost

departmenttodepartmentfrommovedloadsofnumber

sdepartmentindividual

sdepartmentorcentersworkofnumbertotalwhere

costM inimize

1 1


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1 2 3 4 5 6

1

2

3

45

6

40 100 0 0 0

10 40 10 0

0 0 80

50 00

10

0

00

20

20

10

0

0

200

20

0

0 0

Flows of Parts (loads/week)

to


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Interdepartmental Flow of Parts

1 2 3 4 5 6

1

2

3

4

5

6

50 100 0 0 20

30 50 10 0

20 0 100

50 00

Number of loads/week between departments


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Initial Layout

AssemblyDepartment

(1)

PrintingDepartment

(2)

Machine shopDepartment

(3)

ReceivingDepartment

(4)

ShippingDepartment

(5)

TestingDepartment

(6)

Room 1 Room 2 Room 3


Initial Layout Flow Graph Showing


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Initial Layout Flow Graph ShowingLoads/Week

100

50 30

10

50

100

1 2

4 5 6

3


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Cost of Initial Layout

100

50 30

10

50

100

1 2

4 5 6

3

1-2 50 = 50*1

1-3 200 = 100*2

1-6 40 = 20*2

2-3 30 = 30*12-4 50 = 50*1

2-5 10 = 10*1

3-4 40 = 20*2

3-6 100 = 100*1

4-5 50 = 50*1

Total = $570

Cost per load for adjacent locations = $1

Cost per load for non-adjacent locations = $2

L Fl i I iti l L t


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Large Flows in Initial Layout100

50 30

10

50

100

1 2

4 56

3

Largest Flows: 100 for 1-3 & 3-6, so put 3 close to 1 and 6.

50 for 1-2, 2-4 & 4-5 ,


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Improved Layout Flow Graph

100

10050

30

50

2

4

31

5 6


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Improved Layout

PrintingDepartment

(2)

AssemblyDepartment

(1)


(3)

ReceivingDepartment

(4)

ShippingDepartment

(5)

TestingDepartment

(6)




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Cost of Improved Layout

1-2 50 = 50*1

1-3 100 = 100*1

1-6 20 = 20*1

2-3 60 = 30*22-4 50 = 50*1

2-5 10 = 10*1

3-4 40 = 20*2

3-6 100 = 100*1

4-5 50 = 50*1

Total = $480



10050

30

50

2

4

31

5 6

100


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Alternative Improved Layout

50

100100

20

50

1

2

63

4 5

10

Cost of Alternative Improved Layout


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Cost of Alternative Improved Layout

1-2 50 = 50*1

1-3 100 = 100*1

1-6 40 = 20*2

2-3 30 = 30*12-4 50 = 50*1

2-5 20 = 10*2

3-4 20 = 20*1

3-6 100 = 100*1

4-5 50 = 50*1

Total = $460



50

100100

20

50

1

2

63

4 5

10

Is this best?

Alt ti I d L t


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Alternative Improved Layout

PrintingDepartment

(2)

AssemblyDepartment

(1)


(3)

ReceivingDepartment

(4)

ShippingDepartment

(5)

TestingDepartment

(6)



L t E l 2


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Layout Example 2Given the following tables of interdepartmental flows and distances

between locations A-E, locate the five departments to minimize the totaldistancexflow.

Interdepartmental flows

1 2 3 4 51 - 13 18 3 0

2 - 15 0 6

3 - 0 4

4 - 4

A B C D EA - 9 8 12 14

B 9 - 9 6 7

C 8 9 - 4 9

D 12 6 4 - 14

Distances between locations

E 14 7 9 14 -

L t E l 2


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Layout Example 2Largest flow 1-3 (flow=18) should be in closest locations: C&D

Could have: Solution 1: C=1 and D=3 orSolution 2: C=3 and D=1


1 2 3 4 51 - 13 18 3 0

2 - 15 0 6

3 - 0 4

4 - 4

A B C D EA - 9 8 12 14

B 9 - 9 6 7

C 8 9 - 4 9

D 12 6 4 - 14


E 14 7 9 14 -

L t E l 2


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Layout Example 2Next largest flow is 2-3, so 2 should be placed in location closest to 3.

Solution 1: D=3 and closest open location to D is B, so B=2, C=1, D=3.Solution 2: C=3 and closest open location to C is A, so A=2, C=3, D=1.


1 2 3 4 51 - 13 18 3 0

2 - 15 0 6

3 - 0 4

4 - 4

A B C D EA - 9 8 12 14

B 9 - 9 6 7

C 8 9 - 4 9

D 12 6 4 - 14


E 14 7 9 14 -

L t E l 2


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Layout Example 2Next largest flow is 1-2, but 1 and 2 are already located.

So consider next largest flow 2-5.Solution 1: B=2 and closest open location to B is E, so A=4,B=2,C=1, D=3,E=5.Solution 2: A=2 and closest open location to A is B, so A=2,B=5,C=3, D=1,E=4.


1 2 3 4 5

1 - 13 18 3 0

2 - 15 0 6

3 - 0 4

4 - 4

A B C D E

A - 9 8 12 14

B 9 - 9 6 7

C 8 9 - 4 9

D 12 6 4 - 14


E 14 7 9 14 -

Layout Example 2


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Layout Example 2Solution 1: A=4,B=2,C=1, D=3,E=5.

Distance = 13x9 + 18x4 + 3x8 + 15x6 + 6x7 + 4x14 + 4x14 = 457

Solution 2: A=2,B=5,C=3, D=1,E=4.Distance = 13x12 + 18x4 + 3x14 + 15x8 + 6x9 + 4x9 + 4x7 = 508


1 2 3 4 5

1 - 13 18 3 0

2 - 15 0 6

3 - 0 4

4 - 4

A B C D E

A - 9 8 12 14

B 9 - 9 6 7

C 8 9 - 4 9

D 12 6 4 - 14


E 14 7 9 14 -

Solution 1

is best!

Computer Programs for Layout


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Computer Programs for Layout

Many different programs: CRAFT

SPACECRAFT

CRAFT 3-D CORELAP

ALDEP

All are heuristic - not necessarily optimal!!

Work Cells in Process Layouts


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Work Cells in Process Layouts

Special case of product-oriented layout - in aprocess-oriented facility.

Differentmachines brought together to make a product.

Use when high volume warrants special arrangement.

For 1 product or a small group of products.

Temporary arrangement.

Example: Assembly line set up to produce 3000identical parts in a job shop.

Work Cell Floor Plan


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Work Cell Floor Plan

Office

Tool Room Work Cell

Saws Drills

Work Cell Advantages


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Work Cell Advantages

Lower:

Inventory.Floor space.

Direct labor costs.

Higher:

Equipment utilization.Employeeparticipation.

Quality.

Work Cells, Focused WorkC d h F d F


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Centers and the Focused Factory

Work Cell A temporaryassembly-line-orientedarrangementof machines and personnel inwhat is ordinarily a process-oriented facility.

Focused WorkCenter

Apermanentassembly-line-orientedarrangementof machines and personnel inwhat is ordinarily a process-oriented facility.

Focused Factory Apermanent facilityto produce a product orcomponent in a product-oriented facility.

4 Retail/Service Layout


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4. Retail/Service Layout

Maximize product exposure to customers. Maximize profitability per square foot of floor space or

per linear foot of shelf space.

Decision variables:

Arrangement of store.

Store flow pattern.

Allocation of (shelf) space to products.

Video

Retail Layouts - Rules of Thumb


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Retail Layouts Rules of Thumb

Locate high-draw items around the periphery.

Use prominent locations (end aisle locations; first orlast aisle) for high-impulse and high margin items.

Remove crossover aisles to prevent customers from

moving between aisles.

Distribute power items (that dominate a shopping

trip) around store to increase the viewing of other

items. Locate far apart.

Locate on both sides of an aisle.

Grocery Store Layout


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y y

Retail Store Shelf Space


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Retail Store Shelf Space

Consider prominence ofshelf location and numberof facings.

Can use computerized toolsto manage shelf-space.

Track sales and product

location (scanner data).

5facings

PERT

PERT

PERT

PERT

PERT

Servicescape Considerations


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Servicescape Considerations

Ambient conditions.

Background characteristics such as lighting, sound,smell, and temperature.

Spatial layout and functionality.

Customer circulation, aisle width, shelf spacing, etc.

Signs, Symbols, and Artifacts. Various other characteristics of design (carpeting,

greeters, etc.).

5 Warehouse Layout


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5. Warehouse Layout

Balance space utilization & handling cost. Similar to process layout.

Items moved between loading docks

& various storage areas.

Optimum layout depends on:

Variety of items stored.

Number of items picked.

Space Utilization vs. Handling


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Costs

High space utilization (for storage).

Small, narrow aisles.

Product stacked high and deep (not easily accessible).

Ease of material handling.

Wide, short aisles.

Product easily accessible.

Design facility to optimize space utilization andhandling costs tradeoff.

Assigned vs. Random StockL ti


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Locations

Assigned locations for products: May be inefficient use of space.

Easier order picking and re-stocking.

Random locations: More efficient use of space.

Added costs to track location of inventory and open space.

More difficult order picking and re-stocking.

Stock products to optimize cost and efficienciestradeoffs.

Cross Docking (Wal-Mart)


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Cross Docking (Wal Mart) Transferring goods:

From incomingtrucks at receivingdocks.

To outgoingtrucks at shipping docks.

Avoids placing goods intostorage.

Requires suppliers provide

effective addressing (bar codes)and packaging for rapidtransshipment.

In-

comingOutgoing

Order Picking


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Collecting items on a customer order from various

locations in the warehouse.

Sequence items to minimize travel time in

warehouse to pick order.

Also, should locate items to be efficient to pick.

Combine several orders to reduce picking time.

Zoning: Assign separate pickers to differentzones in the warehouse.

Split order among several pickers.

6. Product-Oriented Layout


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6. Product Oriented Layout

Used with product-focussed processes. Facility organized around product.

High volume, low variety.

Types:

Fabrication line - Builds components.

Assembly line - Assembles components intoproducts.

Product-Oriented Layout


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y

Divide work into small tasks. To be done byworkers or machines.

Assign tasks to workstations.

Balance output of each workstation.

To smooth operations of the line.

To make workload equal.

To minimize idle time.

To achieve desired output.

Product-Oriented Requirements


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q

Standardized product.

High production volume.

Stable production quantities.Uniform quality of raw materials &

components.

Product-Oriented Layout Advantages


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Product Oriented Layout Advantages

Lower variable cost per unit.

Lower material handling costs.

Lower work-in-processinventories.

Rapid throughput.

Easier training & supervision.

Product-Oriented LayoutDisadvantages


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Disadvantages

Higher capital investment forspecial equipment.

Any work stoppage stopswhole process.

Lack of flexibility in volume

and product.

Repetitive Layout


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Note: 5 tasks or operations (T1-T5);

3 work stations (orange rectangles)

T1 T3

T2

T4

T5

Work Station 1

Office

Belt Conveyor

WorkStation 3

Work Station 2

Assembly Line Balancing Steps


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y g p

1. Determine tasks (operations) & task times.2. Determine sequence of tasks.

3. Draw precedence diagram.

4. Calculate cycle time .

5. Calculate minimum number of work stations, N.

6. Assign tasks.7. Calculate efficiency.

Assembly Line Balancing Data


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Usually we are given:

Production rate.

Units of product to be produced per unit time.

Production time available per day.

Tasks (operations) & task times.

Sequence of tasks.

Assembly Line BalancingGeneral Procedure


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General Procedure

1. Determine cycle time - The time betweenproduction of successive units. (May bemeasured in seconds, minutes, etc.)

2. Calculate the theoretical minimum number ofworkstations, denoted N. (May not be achievable.)

3. Assign tasksto workstations to balance the line.Compute the efficiency.

Assembly Line Balancing Equations


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y g q

Cycle time =Production time available

Production rate

Minimum

number ofwork stations

Task timesCycle time

Efficiency =

=

Task times

* (Cycle time)(Actual numberof work stations)

= N Rounded up

Assembly Line Balancing Example


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Task Time PredecessorA 0.1 min. -B 0.7 min. AC 1.0 min. B

D 0.5 min. CE 0.2 min. D

2.5 min.

Immediate

A B C D E

0.1 0.20.7 1.0

0.5

Suppose we want to

produce 300 units/day

and 8 hours are

available each day.



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Task Time PredecessorA 0.1 min. -B 0.7 min. AC 1.0 min. BD 0.5 min. CE 0.2 min. D

2.5 min.

Immediate

Suppose we want toproduce 300 units/day

and 8 hours are

available each day.

nsworkstatioortesminu

tesminu

N

unittesminudayunits

daytesminutimecycle

25625.16.1

5.2

/6.1/300

/480

So assign tasks A-E to 2 workstations, where neither workstation

should exceed 1.6 minutes.



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A B C D E

0.1 0.20.7 1.

0

0.5

Suppose we want toproduce 300 units/day

and 8 hours are

available each day.

Can not use only 2 workstations! Must use 3.

Efficiency=2.5/(3*1.6) = 52.1%

Task Time PredecessorA 0.1 min. -B 0.7 min. AC 1.0 min. BD 0.5 min. CE 0.2 min. D

2.5 min.

Immediate



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A B C D E0.1 0.20.7 1.

00.5

Both of these can

produce 300/day in8 hours.

Efficiency=2.5/(3*1.6) = 52.1%

A B C D E

0.1 0.20.7 1.

0

0.5

Efficiency=2.5/(3*1.6) = 52.1%

Better balance!

Note: this line could produce 300 units in 5 hours (1 per minute)

Efficiency=2.5/(3*1.0) = 83.3%



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A B C D E

0.1 0.20.7 1.0

0.5

If 2 workstations were required, then it will take more than 8 hours

to produce 300 units.

Cycle time = 1.7 minutes

Efficiency=2.5/(2*1.7) = 73.5%

Time to produce 300 units

1.7 min/unit*300 units = 510 minutes = 8.5 hours

Assembly Line Balancing Heuristics


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Longest (or shortest) task time.

Choose task with longest (or shortest) operation time.

Most following tasks.

Choose task with largest number of following tasks.

Ranked positional weight.

Choose task where the sum of the times for each

following task is longest.

Least number of following tasks.

Choose task with fewest subsequent tasks.

Ranked Positional Weight Heuristic


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Positional weight = Sum of times for a task and all

tasks that must follow it.

1. Calculate positional weight for each task.

2. Assign task with largest positional weight to theearliest workstation where it fits.- Obey precedence relations.- Do not exceed cycle time.

3. Repeat step 2 until all tasks are assigned.

Line Balancing Example 2


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Task Time PredecessorA 0.2 min. -B 0.6 min. A,CC 0.5 min. -

D 0.3 min. -E 1.0 min. B,DF 0.2 min. DG 0.9 min. E,F

3.7 min.

Immediate

Suppose we want toproduce 450 units/dayand 8 hours are

available each day.

Line Balancing Example 2


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Task Time PredecessorA 0.2 min. -B 0.6 min. A,CC 0.5 min. -D 0.3 min. -E 1.0 min. B,D

F 0.2 min. DG 0.9 min. E,F3.7 min.

Immediate

Suppose we want toproduce 450 units/dayand 8 hours are

available each day.

nsworkstatioortesminu

tesminuN

unittesminu

dayunits

daytesminutimecycle

4...47.30667.1

7.3

/0667.1

/450

/480

Precedence Diagram - Example 2


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A

BEC

D F

G

0.2

0.5

0.3

0.6

0.2

1.0

0.9

Example 2 - Positional Weight


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Task Time Predecessor weightA 0.2 min. - 2.7B 0.6 min. A,C 2.5C 0.5 min. - 3.0

D 0.3 min. - 2.4E 1.0 min. B,D 1.9F 0.2 min. D 1.1G 0.9 min. E,F 0.9

3.7 min.

Immediate Positional

Example 2 - Assign Tasks


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Task Time Predecessor weightA 0.2 min. - 2.7B 0.6 min. A,C 2.5C 0.5 min. - 3.0D 0.3 min. - 2.4

E 1.0 min. B,D 1.9F 0.2 min. D 1.1G 0.9 min. E,F 0.9

3.7 min.


Cycle time = 1.07 min.

N= 4 workstations

WS1 WS2 WS3 WS4C(0.5)

A(0.2)

Example 2 - Assign Tasks (cont.)


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3.7 min.



N= 4 workstations

WS1 WS2 WS3 WS4C(0.5) B(0.6)

A(0.2)D(0.3)

Example 2 - Assign Tasks (cont.)

I di t P iti l


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3.7 min.



N= 4 workstations

WS1 WS2 WS3 WS4C(0.5) B(0.6) E(1.0) G(0.9)

A(0.2) F(0.2)D(0.3)

Efficiency =

3.7/(4*1.07) = 86.4%

Precedence Diagram - Example 2


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A

B

EC

D F

G

0.2

0.5

0.3

0.6

0.2

1.0

0.9

WS1 WS2

WS3

WS4

Example 2 - Final Comment

Immediate


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Task Time PredecessorA 0.2 min. -B 0.6 min. A,CC 0.5 min. -D 0.3 min. -

E 1.0 min. B,DF 0.2 min. DG 0.9 min. E,F

3.7 min.

Immediate

Could use a cycle time of

1 minute & produce 450

units in 7.5 hours

WS1 WS2 WS3 WS4C(0.5) B(0.6) E(1.0) G(0.9)

A(0.2) F(0.2)D(0.3)

Efficiency =

3.7/(4*1.0) = 92.5%

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