Assembly Line BalancingAssembly Line Balancing

Applied Management Science for Decision Making, 1e Applied Management Science for Decision Making, 1e © 2012 Pearson Prentice-Hall, Inc. Philip A. Vaccaro , PhD© 2012 Pearson Prentice-Hall, Inc. Philip A. Vaccaro , PhD

Assembly Line BalancingAssembly Line Balancing

The assignment of tasks to work stations along an assembly line in such a way as

to achieve the same or close to sameworking times at each work station.

THE GOAL IS TO CREATE A SMOOTH,THE GOAL IS TO CREATE A SMOOTH,CONTINUOUS FLOW OF PRODUCT THROUGHCONTINUOUS FLOW OF PRODUCT THROUGH

THE ASSEMBLY LINE FOR MAXIMUMTHE ASSEMBLY LINE FOR MAXIMUMPRODUCTIVITY AND MINIMUM IDLE TIMEPRODUCTIVITY AND MINIMUM IDLE TIME

AT EACH WORK STATIONAT EACH WORK STATION

Assembly Line BalancingAssembly Line BalancingAPPLICATIONS

Cafeteria line

Carwash line

Appliance manufacturing line

Automobile manufacturing line

Registry of Motor Vehicles office line

Disassembly line

Fabrication line

Physical exams for military recruits

- POULTRY SLAUGHTER- AUTOMOBILE RECYCLING

- PRODUCTION OF PARTS VIA SERIES OF MACHINES

Assembly Line BalancingCafeteria Line

Station 1Station 1Trays, Plates, Utensils

Station 2Station 2Appetizers

Station 3Station 3Entrees

Station 4Station 4Desserts

Station 5Station 5Cashier

Assembly Line BalancingAssembly Line BalancingPoultry Dissassembly Line

Station 1

Station 2

Station 3

Station 4

Station 5

Station 6

Assembly Line BalancingRaw Recruit Physical Examinations

14 Stations includingReception

Eye ExaminationChest X-ray

Weight + Height MeasurementPsychological

Heart Rate

Assembly Line BalancingAssembly Line BalancingWHEN IT IS DONEWHEN IT IS DONE

BEFORE ACTUAL PRODUCTIONIN WESTERN MANUFACTURING

SYSTEMS

DURING ACTUAL PRODUCTIONIN ASIAN MANUFACTURING

SYSTEMS

Individual Task TimesIndividual Task Times

These are set well in advance by industrial engineers and time & motion specialists

They are called standard task times and consist of normal time to perform a particular task and extra time allowances for fatigue, personal needs, and unavoidable, but recurring delays.

The Assembly Line BalancingThe Assembly Line Balancing Concept Concept

Station1

Station2

Station3

The Assembly Line

towarehouse

orretailer

At the end of every cycle, each station hands itsAt the end of every cycle, each station hands its work-in-process unit to the next station.work-in-process unit to the next station.

A cycle is the amount of time that a work-in-process unit canstay in a work station before it must move onto the next.

The Assembly Line BalancingThe Assembly Line Balancing Concept Concept

Station1

Station2

Station3

The Assembly Line

towarehouse

orretailer

The effective production rate for the assembly line The effective production rate for the assembly line equals one completed product every equals one completed product every 1010 minutes, minutes,

even though each unit requires 30 minutes to build!even though each unit requires 30 minutes to build!

If the cycle time were 10 minutes, each station would hand its work-in-processunit over to the next station at the end of 10 minutes.

The The Assembly Line Balancing Assembly Line Balancing ConceptConcept

Station 1( 10 Minutes )

Station 2( 10 Minutes )

Station 3( 10 Minutes )

Total Time( 30 Minutes )

Task A( 10 minutes )

Task B( 5 minutes )

Task D( 2 minutes )

Task C( 5 minutes )

Task E( 3 minutes )

Task F( 5 minutes )

10 Minutes Productive

Time

10 Minutes Productive

Time

10 Minutes Productive

Time

30 MinutesTotal Productive Time

0 Minutes Idle Time

0 Minutes Idle Time

0 Minutes Idle Time

0 MinutesTotal Idle Time

Assumethe cycletime is

10minutes

A A PERFECTLY-BALANCEDPERFECTLY-BALANCED ASSEMBLY LINE ASSEMBLY LINE

The The Assembly Line BalancingAssembly Line Balancing ConceptConcept

Tasks are measured in seconds and vary widely.

It is impossible to as- sign tasks to all work stations so as to get exact work times at each station per cycle. Therefore, a perfectly balanced assembly line does not exist !

The The Assembly Line Balancing Assembly Line Balancing ConceptConcept

Station 1( 10 Minutes )

Station 2( 10 Minutes )

Station 3( 10 Minutes )

Total Time( 30 Minutes )

Task A ( 9 minutes )

Task B( 4 minutes )

Task D( 2 minutes )

Task C( 4 minutes )

Task E( 2 minutes )

Task F( 5 minutes )

9 Minutes Productive

Time

8 Minutes Productive

Time

9 Minutes Productive

Time

26 MinutesTotal Productive Time

1 Minute Idle Time

2 Minutes Idle Time

1 Minute Idle Time

4 MinutesTotal Idle Time

Assumethe cycletime is

10minutes

A A NOTNOT PERFECTLY-BALANCEDPERFECTLY-BALANCED ASSEMBLY LINE ASSEMBLY LINE

Assembly Line Balancing Assembly Line Balancing StepsSteps

Provide the tools, equipment, and work methodsProvide the tools, equipment, and work methods to be used in producing a product or service at ato be used in producing a product or service at a desired volume.desired volume.

Assembly Line Balancing Assembly Line Balancing StepsSteps

Provide the tools, equipment, and work methodsProvide the tools, equipment, and work methods to be used in producing a product or service at ato be used in producing a product or service at a desired volume.desired volume.

Identify the Identify the standard time standard time for each assembly or for each assembly or service task involved in the creation of the productservice task involved in the creation of the product or service.or service.

Assembly Line Balancing Assembly Line Balancing StepsSteps

Provide the tools, equipment, and work methodsProvide the tools, equipment, and work methods to be used in producing a product or service at ato be used in producing a product or service at a desired volume.desired volume.

Identify the Identify the standard time standard time for each assembly or for each assembly or service task involved in the creation of the productservice task involved in the creation of the product or service.or service.

Identify the Identify the precedence relationships.precedence relationships.THE ORDER IN WHICH THE TASKS MUST BE PERFORMED

Practical Problem StatementPractical Problem Statement

Develop the Assembly Line !

A firm wants to produce160 units of a producteach 8-hour day on an

assembly line.

Nine ( 9 ) separatetasks are neededto complete eachunit of product.

Assume no break timeand no paid lunch time

Task Predecessor Standard TimeTask Predecessor Standard Time

A none 60

B A 80

C none 30

D C 40

E B,D 40

F none 50

G F 100

H D,G 70

I E,H 30

ΣΣ = = 500 seconds500 seconds

The Precedence DiagramThe Precedence Diagram

A network showing the sequential relationships among all tasks to be performed on the assembly line, together with their respective standard times.

An optional, useful tool for avoiding precedence relationship violations when assigning tasks to work stations, without benefit of the computer.

The Precedence DiagramThe Precedence DiagramTHE ORDER IN WHICH TASKS MUST BE PERFORMED

A60

C30

F50

B80

D40

G100

E40

H70

I30

The Cycle TimeThe Cycle Time

SHOWN IN SECONDSSHOWN IN SECONDS

The maximum period of time that a work-in-process

unit can stay in any givenwork station before it mustmove on to the next work

station.

The Cycle Time FormulaThe Cycle Time Formula

Total Available Daily Production Time

Daily Production Quota

28,800 Seconds

160 Units( FROM THE PROBLEM )

= 180 Seconds

The Minimum Number of Work StationsThe Minimum Number of Work Stations

The minimum number of work stations that theThe minimum number of work stations that the new assembly line, when balanced, will contain.new assembly line, when balanced, will contain.

The Minimum Number of Work StationsThe Minimum Number of Work Stations

The minimum number of work stations that theThe minimum number of work stations that the new assembly line, when balanced, will contain.new assembly line, when balanced, will contain.

The actual number of work stations may well The actual number of work stations may well exceed the minimum number by one or more. exceed the minimum number by one or more.

The Minimum Number of Work StationsThe Minimum Number of Work Stations

The minimum number of work stations that theThe minimum number of work stations that the new assembly line, when balanced, will contain.new assembly line, when balanced, will contain.

The actual number of work stations may well The actual number of work stations may well exceed the minimum number by one or more. exceed the minimum number by one or more.

Also known as the Also known as the theoretical minimumtheoretical minimum number of work stations.number of work stations.

The FormulaThe Formula

Total Task Time Per Unit of Product

The Cycle Time

500 Seconds

180 Seconds= 2.77 ≈ 3.00

FRACTIONS ARE ALWAYS ROUNDED UP( i.e. “2.01” becomes “3.00” )

MINIMUM NUMBER OF WORK STATIONS

The Line-Balancing SpreadsheetThe Line-Balancing Spreadsheet To assign individual tasks to each work station.

The theoretical minimum number of work stations. The cycle time for each work station. The cycle time for the entire assembly line. The productive time per cycle at each work station. The idle time per cycle at each work station.

SHOWS

The Line Balancing SpreadsheetThe Line Balancing Spreadsheet

Cycle Time180

seconds

180seconds

180seconds

540seconds

Station

1

Station

2

Station

3Productive

Time

Per Cycle

Idle

Time

Per Cycle

Task Assignment HeuristicTask Assignment Heuristic

From the Greek From the Greek έύρϊσκεινέύρϊσκειν ( heuriskein ) ( heuriskein ) meaning “to discover” or “to guide”.meaning “to discover” or “to guide”.

Task Assignment HeuristicTask Assignment Heuristic

From the Greek From the Greek έύρϊσκεινέύρϊσκειν ( heuriskein ) ( heuriskein ) meaning “to discover” or “to guide”.meaning “to discover” or “to guide”.

A A rule of thumb rule of thumb or guideline for finding or guideline for finding a solution in general.a solution in general.

Task Assignment HeuristicTask Assignment Heuristic

From the Greek From the Greek έύρϊσκεινέύρϊσκειν ( heuriskein ) ( heuriskein ) meaning “to discover” or “to guide”.meaning “to discover” or “to guide”.

A A rule of thumb rule of thumb or guideline for finding or guideline for finding a solution in general.a solution in general.

Here, a particular Here, a particular rationale rationale for assigning for assigning tasks to work stations in line balancing.tasks to work stations in line balancing.

Heuristic SelectionHeuristic Selection

I. The LOT rule – longest operating time

II. The SOT rule – shortest operating time

III. The MFT rule – the most follower tasks

IV. The LFT rule – the least follower tasks

V. The Ranked Positional Weight or Highest

Sum rule

FIVE POPULAR HEURISTICS FOR LINE BALANCING

The LOT Assignment HeuristicThe LOT Assignment Heuristic

Also known as the longest operating time rule.

Assigns the longest tasks to the work stations first.

SUBJECT TO MAINTAINING THE PRECEDENCERELATIONSHIPS AMONG THE WORK TASKS

Task A

before

B

B and D

before E

Precedence Diagram LegendPrecedence Diagram Legend

X

Y

Z

NON-CANDIDATE TASKS

( SHOWN IN BLUE )

A

D

AN ASSIGNED TASK( SHOWN WITH “X” ACROSS )

X

CANDIDATES FOR THE NEXTTASK ASSIGNMENT

( SHOWN IN RED )

B

C DX

DX

The Precedence DiagramThe Precedence Diagram

A60

C30

F50

B80

D40

G100

E40

H70

II3030

The Precedence DiagramThe Precedence Diagram

A60

C30

F50

B80

D40

G100

E40

H70

II3030

1st TASK ASSIGNMENTCANDIDATES FOR

STATION 1

The Line Balancing SpreadsheetThe Line Balancing Spreadsheet

Cycle Time180

seconds

180seconds

180seconds

540seconds

Station

1

Station

2

Station

3Productive

Time

Per Cycle

Idle

Time

Per Cycle

TASK ATASK A( 60 sec )( 60 sec )

The Precedence DiagramThe Precedence Diagram

A60

C30

F50

B80

D40

G100

E40

H70

II3030

2nd TASK ASSIGNMENTCANDIDATES FOR

STATION 1X

The Line Balancing SpreadsheetThe Line Balancing Spreadsheet

Cycle Time180

seconds

180seconds

180seconds

540seconds

Station

1

Station

2

Station

3Productive

Time

Per Cycle

Idle

Time

Per Cycle

TASK ATASK A( 60 sec )( 60 sec ) TASK BTASK B( 80 sec )( 80 sec )

The Precedence DiagramThe Precedence Diagram

A60

C30

F50

B80

D40

G100

E40

H70

II3030

3rd TASK ASSIGNMENTCANDIDATES FOR

STATION 1X X

The Line Balancing SpreadsheetThe Line Balancing Spreadsheet

Cycle Time180

seconds

180seconds

180seconds

540seconds

Station

1

Station

2

Station

3Productive

Time

Per Cycle

Idle

Time

Per Cycle

TASK A ( 60 sec )TASK A ( 60 sec )TASK B ( 80 sec )TASK B ( 80 sec )TASK C ( 30 sec )TASK C ( 30 sec )

1010seconds

The Precedence DiagramThe Precedence Diagram

A60

C30

F50

B80

D40

G100

E40

H70

II3030

1st TASK ASSIGNMENTCANDIDATES FOR

STATION 2X X

X

The Line Balancing SpreadsheetThe Line Balancing Spreadsheet

Cycle Time180

seconds

180seconds

180seconds

540seconds

Station

1

Station

2

Station

3Productive

Time

Per Cycle

Idle

Time

Per Cycle

TASK A ( 60 sec )TASK A ( 60 sec )TASK B ( 80 sec )TASK B ( 80 sec )TASK C ( 30 sec )TASK C ( 30 sec )

1010secondsseconds

TASK FTASK F( 50 sec )( 50 sec )

The Precedence DiagramThe Precedence Diagram

A60

C30

F50

B80

D40

G100

E40

H70

I30

2nd TASK ASSIGNMENTCANDIDATES FOR

STATION 2X X

X

X

The Line Balancing SpreadsheetThe Line Balancing Spreadsheet

Cycle Time180

seconds

180seconds

180seconds

540seconds

Station

1

Station

2

Station

3Productive

Time

Per Cycle

Idle

Time

Per Cycle

TASK A ( 60 sec )TASK A ( 60 sec )TASK B ( 80 sec )TASK B ( 80 sec )TASK C ( 30 sec )TASK C ( 30 sec )

1010secondsseconds

TASK F ( 50 sec)TASK F ( 50 sec) TASK G (100 sec)TASK G (100 sec)

3030secondsseconds

The Precedence DiagramThe Precedence Diagram

A60

C30

F50

B80

D40

G100

E40

H70

I30

1st TASK ASSIGNMENTCANDIDATES FOR

STATION 3X X

X

X X

The Line Balancing SpreadsheetThe Line Balancing Spreadsheet

Cycle Time180

seconds

180seconds

180seconds

540seconds

Station

1

Station

2

Station

3Productive

Time

Per Cycle

Idle

Time

Per Cycle

TASK A ( 60 sec )TASK A ( 60 sec )TASK B ( 80 sec )TASK B ( 80 sec )TASK C ( 30 sec )TASK C ( 30 sec )

1010secondsseconds

TASK F (50 sec)TASK F (50 sec) TASK G (100 sec)TASK G (100 sec)

3030secondsseconds

TASK DTASK D( 40 sec )( 40 sec )

The Precedence DiagramThe Precedence Diagram

A60

C30

F50

B80

D40

G100

E40

H70

I30

2nd TASK ASSIGNMENTCANDIDATES FOR

STATION 3X X

X

X X

X

The Line Balancing SpreadsheetThe Line Balancing Spreadsheet

Cycle Time180

seconds

180seconds

180seconds

540seconds

Station

1

Station

2

Station

3Productive

Time

Per Cycle

Idle

Time

Per Cycle

TASK A ( 60 sec )TASK A ( 60 sec )TASK B ( 80 sec )TASK B ( 80 sec )TASK C ( 30 sec )TASK C ( 30 sec )

10seconds

TASK F (50 sec)TASK F (50 sec) TASK G (100 sec)TASK G (100 sec)

3030secondsseconds

TASK DTASK D( 40 sec )( 40 sec )TASK HTASK H

( 70 sec )( 70 sec )

The Precedence DiagramThe Precedence Diagram

A60

C30

F50

B80

D40

G100

E40

H70

I30

3rd TASK ASSIGNMENTCANDIDATES FOR

STATION 3X X

X

X X

X

X

The Line Balancing SpreadsheetThe Line Balancing Spreadsheet

Cycle Time180

seconds

180seconds

180seconds

540seconds

Station

1

Station

2

Station

3Productive

Time

Per Cycle

Idle

Time

Per Cycle

TASK A ( 60 sec )TASK A ( 60 sec )TASK B ( 80 sec )TASK B ( 80 sec )TASK C ( 30 sec )TASK C ( 30 sec )

1010secondsseconds

TASK F (50 sec)TASK F (50 sec) TASK G (100 sec)TASK G (100 sec)

3030secondsseconds

TASK D (40 sec)TASK D (40 sec)TASK H (70 sec)TASK H (70 sec)TASK E (40 sec)TASK E (40 sec)

The Precedence DiagramThe Precedence Diagram

A60

C30

F50

B80

D40

G100

E40

H70

I30

4th TASK ASSIGNMENTCANDIDATES FOR

STATION 3X X

X

X X

X

X

X

The Line Balancing SpreadsheetThe Line Balancing Spreadsheet

Cycle Time180

seconds

180seconds

180seconds

540seconds

Station

1

Station

2

Station

3Productive

Time

Per Cycle

Idle

Time

Per Cycle

TASK A ( 60 sec )TASK A ( 60 sec )TASK B ( 80 sec )TASK B ( 80 sec )TASK C ( 30 sec )TASK C ( 30 sec )

1010secondsseconds

TASK F (50 sec)TASK F (50 sec) TASK G (100 sec)TASK G (100 sec)

3030secondsseconds

TASK D (40 sec)TASK D (40 sec)TASK H (70 sec)TASK H (70 sec)TASK E (40 sec)TASK E (40 sec)TASK I (30 sec)TASK I (30 sec)

00secondsseconds

The Line Balancing SpreadsheetThe Line Balancing Spreadsheet

Cycle Time180

seconds

180seconds

180seconds

540seconds

Station

1

Station

2

Station

3Productive

Time

Per Cycle

Idle

Time

Per Cycle

TASK A ( 60 sec )TASK A ( 60 sec )TASK B ( 80 sec )TASK B ( 80 sec )TASK C ( 30 sec )TASK C ( 30 sec )

1010secondsseconds

TASK F (50 sec)TASK F (50 sec) TASK G (100 sec)TASK G (100 sec)

3030secondsseconds

TASK D (40 sec)TASK D (40 sec)TASK H (70 sec)TASK H (70 sec)TASK E (40 sec)TASK E (40 sec)TASK I (30 sec)TASK I (30 sec)

00secondsseconds

500seconds

40seconds

TOTAL

Evaluating The Balanced LineEvaluating The Balanced Line

Efficiency =

total productive time on the assemblyline per cycle

total available time on the assemblyline per cycle

500 seconds

540 seconds= 92.6%

EFFICIENCY => 90% IS CONSIDERED ACCEPTABLE

Evaluating The Balanced LineEvaluating The Balanced Line

Balance Delay Factor ( % IDLE TIME )

line idle time per cycle

line total time per cycle=

40 seconds

540 seconds= = 7.4%

A BALANCE DELAY FACTOR=< 10% IS CONSIDERED TO

BE ACCEPTABLE

Evaluating The Balanced LineEvaluating The Balanced Line

Effectiveness is achieved if theassembly line meets management’s

daily production quota

THE EMPLOYMENT OF THEMAXIMUM ALLOWABLE CYCLE

TIME GUARANTEED DAILY QUOTA COMPLIANCE !

10 10 10

Line Balancing under QM for WindowsLine Balancing under QM for Windows

We Select The ‘Assembly Line Balancing’

Program

We Desire ToSolve A New

Problem

The Dialog BoxAppears

Nine ( 9 ) TasksNeed To BeAssigned

To Work Stations

Task Times AreNormally Stated

In Seconds

We Label Tasksas A,B,C,D, etc.

THE DATA INPUT TABLEPROVIDES COLUMNSFOR LISTING EACH

TASK’S PREDECESSOR(S)

THE SOFTWAREDETERMINES

HOW MANY COLUMNSSHOULD BE PROVIDED

FOR LISTING PREDECESSOR TASKS

The Predecessor TasksMust Be Shown InIndividual Cells,Alphabetically

Here, We Entered TheCycle Time For

The Software ToWork With

We Selected The“LOT” Assignment

HeuristicFor Balancing This

Assembly Line

Line Efficiency = 92.59%

Balance Delay Factor = 7.41%

Idle Time Per Cycle,Per Work Station

Task Candidates

Tasks A,B,C assignedTo Work Station # 1

This Is The Program’s Way of Asking Us

If This Is The CorrectPrecedence RelationshipAmong The Nine Tasks

The Amount of ProductiveTime Per Cycle

In Each Work Station

The Cycle Timeis

180 seconds

If task “ I ” had a standard time offorty seconds…..

1. What changes must be made to the line-balancing spreadsheet?

2. How would the efficiency of the line be affected?

NEW SCENARIO

??

The New Precedence DiagramThe New Precedence Diagram

A60

C30

F50

B80

D40

G100

E40

H70

I40

TASK“ I “

BECOMESFORTY

SECONDS

The Line-Balancing SpreadsheetThe Line-Balancing Spreadsheet

Cycle time

180seconds

180seconds

180seconds

180seconds

Σ

720

station

1

station

2

station

3

station

4TASK ATASK A

TASK BTASK B

TASK CTASK C

170 seconds

TASK FTASK F

TASK GTASK G

150 seconds

TASK DTASK D

TASK HTASK H

TASK ETASK E

150 seconds

TASK I

40 seconds

Σ = 510seconds

Σ = 210seconds

MODIFIED FOR TASK “ I ” NEW STANDARD TIME

seconds

ProductiveTime

Per Cycle

Idle Time

Per Cycle10 seconds 30 seconds 30 seconds

140seconds

Spreadsheet ModificationsSpreadsheet Modifications

A 4th work station would need to be opened exclusively for task “I”.

Total assembly line available time per cycle would jump to 720 seconds ( 180 secs x 4 stations )

Total assembly line idle time per cycle would jump to 210 seconds ( under any assignment heuristic )

The balanced line would no longer be efficient ( 71% )

Evaluating The Balanced LineEvaluating The Balanced LineFOURTH STATION ADDED FOR TASK “I”

Efficiency = = 71%

Balance Delay Factor

210 seconds

720 seconds= = 29%

THE LINE FAILS IN THE LINE FAILS IN EFFICIENCYEFFICIENCY

510 seconds

720 seconds

Minimum Allowable Cycle TimeMinimum Allowable Cycle Time THE “OTHER” CYCLE TIMETHE “OTHER” CYCLE TIME

Cycle time based on the bottleneck task*

No guarantee that the daily production quota will be met

Line efficiency will most likely change under this cycle time

* THE LONGEST TASK TIME

Minimum Allowable Cycle TimeMinimum Allowable Cycle Time

From the text example, the longest task is “G” which takes 100 seconds to perform.

The minimum allowable cycle time therefore is 100 seconds.

The theoretical minimum number of work stations:

EXAMPLE

500 seconds

100 seconds= 5

ASSUME TASK “ I “ = 30 SECONDS

100seconds

100seconds

100seconds

100seconds

100seconds

100seconds Σ 600

seconds

Station

1

Station

2

Station

3

Station

4

Station

5

Station

6

Productive

Time

Per Cycle

TASK ATASK A

TASK CTASK C

90 seconds

TASK BTASK B

80 seconds

TASK F

TASK D

90 seconds

TASK G

100 seconds

TASK HTASK H

70 seconds

TASK ETASK E

TASKTASK II

70 seconds

Σ 500seconds

Idle

Time

Per Cycle

Σ 100seconds

Minimum Allowable Cycle TimeMinimum Allowable Cycle TimeLINE-BALANCING SPREADSHEET

CycleTime

10seconds

20seconds

10seconds

0seconds

30seconds

30seconds

ASSUME TASK “ I ” = 30 SECONDS

WE ENDED UP WITH SIX WORK STATIONS IN ORDER TO ASSIGN ALL 9 TASKS

Evaluating The Balanced LineEvaluating The Balanced Line MINIMUM ALLOWABLE CYCLE TIME

Efficiency = 500 seconds = .833 = 83.3%

600 seconds

Balance DelayFactor = 100 seconds = .167 = 16.7%

600 seconds

THE LINE FAILS TOMEET ACCEPTABLE

EFFICIENCY

0 0 0

ASSUME TASK “I” = 30 SECONDS

100seconds

100seconds

100seconds

100seconds

100seconds

100seconds Σ 600

seconds

Station

1

Station

2

Station

3

Station

4

Station

5

Station

6

Productive

Time

Per Cycle

TASK ATASK A

TASK CTASK C

90 seconds

TASK BTASK B

80 seconds

TASK FTASK F

TASK DTASK D

90 seconds

TASK GTASK G

100 seconds

TASK HTASK H

70 seconds

TASK ETASK E

TASKTASK II

80 seconds

Σ 510seconds

Idle

Time

Per Cycle

Σ 90seconds

Minimum Allowable Cycle TimeMinimum Allowable Cycle TimeLINE-BALANCING SPREADSHEET

CycleTime

10seconds

20seconds

10seconds

0seconds

30seconds

20seconds

ASSUME TASK “ I ” = 40 SECONDS

Evaluating The Balanced LineEvaluating The Balanced Line MINIMUM ALLOWABLE CYCLE TIME

Efficiency = 510 seconds = .850 = 85.0%

600 seconds

Balance DelayFactor

= 90 seconds = .150 = 15.0%

600 seconds

THE LINE FAILS TOMEET ACCEPTABLE

EFFICIENCY

0 0 0

ASSUME TASK “ I ” = 40 SECONDS

Evaluating The Balanced LineEvaluating The Balanced LineEffectiveness

Under

Maximum Allowable

Cycle Time

28,800 seconds

180 seconds

= 160 units produced daily

Effectiveness

Under

Minimum Allowable

Cycle Time

28,800 seconds

100 seconds

= 288 units produced daily

_________________________ __________________________

Scoreboard

Type Type CycleCycle

Cycle Cycle TimeTime

Task Task

“ “ I ”I ”

EfficiencyEfficiency BalanceBalance

Delay Delay MAXIMUM

Allowable180 seconds 30 seconds30 seconds 92.59%92.59% 7.41%

MAXIMUM

Allowable180 seconds 40 seconds 70.83% 29.17%

MINIMIN

Allowable100 seconds 30 seconds30 seconds 83.33% 16.67%

MINIMIN

Allowable100 seconds 40 seconds 85.00% 15.00%

ACCEPTABLE EFFICIENCYACCEPTABLE EFFICIENCY

Line Balancing under QM for WindowsLine Balancing under QM for WindowsADDITIONAL SCENARIOS

The MaximumAllowable

Cycle Time

Assume Task “ I “

Equals 40 Seconds

TheLOT Assignment

Heuristic

Rebalanced Assembly Line

Maximum Allowable Cycle Time

Task “ I “ = 40 Seconds

LOT Assignment Heuristic

The Minimum Allowable

Cycle Time

Task “ I “ Equals

30 Seconds

TheLOT Assignment Heuristic

Is Employed

Rebalanced Assembly Line

Minimum Allowable Cycle Time

Task “ I “ = 30 Seconds

LOT Assignment Heuristic

LOT Assignment Heuristic

Task “ I “ Equals 40 Seconds

TheMinimum Allowable

Cycle Time

Rebalanced Assembly Line

LOT Assignment Heuristic

Minimum Allowable Cycle Time

Task “ I “ = 40 Seconds

Scoreboard

Type Type CycleCycle

Cycle Cycle TimeTime

Task Task

“ “ I ”I ”

EfficiencyEfficiency BalanceBalance

Delay Delay MAXIMUM

Allowable180 seconds 30 seconds30 seconds 92.59%92.59% 7.41%

MAXIMUM

Allowable180 seconds 40 seconds 70.83% 29.17%

MINIMIN

Allowable100 seconds 30 seconds30 seconds 83.33% 16.67%

MINIMIN

Allowable100 seconds 40 seconds 85.00% 15.00%

ACCEPTABLE EFFICIENCYACCEPTABLE EFFICIENCY

Decision ProcessDecision ProcessLine Efficiency < 90%

Try Minimum Allowable Cycle Time

Line Efficiency Still < 90%

Product RedesignWorker Training

Faster Equipmentetc.

Rebalance Line

OUTSIDETHE

REALM OF

LINEBALANCING

MAYTAKE

MONTHSTO

ACCOMPLISH

Why Labor Idleness Is CostlyWhy Labor Idleness Is Costly

Average worker wage rate is $25.00 per hour

Ten (10) seconds of idle time per cycle in one particular work station.

One hundred sixty (160) cycles per work day.

ASSUME THE FOLLOWING

IDLE TIME COSTSIDLE TIME COSTS

1 Station1 Station$11.20$11.20DailyDaily

1 Station1 Station$2,800.00$2,800.00AnnuallyAnnually

20 Stations20 Stations$56,000.00$56,000.00AnnuallyAnnually

5 Plants5 Plants$250,000.00$250,000.00

AnnuallyAnnually

Assembly Line EfficiencyAssembly Line Efficiency

The overall efficiency of the assembly line cannot be changed by employing a different task assign- ment heuristic. This would merely reshuffle the tasks among the work stations.

MFTSO

T

LFT

A FINAL WORDA FINAL WORD

Fairness in Line BalancingFairness in Line Balancing

Experimenting with different task assignment heuristics may prove useful if management is seeking a more equitable distribution of work among all of its work station employees.

Per Cycle STATION 1 STATION 2 STATION 3PRODUCTIVE TIME 167 seconds 167 seconds 167 seconds

IDLE TIME 13 seconds 13 seconds 13 secondsAVAILABLE TIME 180 seconds 180 seconds 180 seconds

Assembly Line BalancingAssembly Line Balancing

THE ENDTHE END

Applied Management Science for Decision Making, 1e Applied Management Science for Decision Making, 1e © 2011 Pearson Prentice-Hall, Inc. Philip A. Vaccaro, PhD© 2011 Pearson Prentice-Hall, Inc. Philip A. Vaccaro, PhD