materi # 14 - line balancing-1(2)

7/30/2019 Materi # 14 - Line Balancing-1(2)

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LINE BALANCING

SIMPLE ASSEMBLY LINEBALANCING PROBLEM


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WHAT IS LINE BALANCING

PROBLEM????Simple Assembly-Line Balancing Problem (SALBP) :

Balancing work station through minimizing delay, and Continuous operation for assembly line (Elsayed dan Boucher,

1994).

Batasan-batasan dalam mendesain sebuah lini perakitan: precedence relationship, Number of work station : 1 S N, Cycle time : maxWiTsTc.

Operator performance : assign the right operator to the rightjob.

Layout : minimizing the distance between stations.


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ADA 2 MACAM SALBP:

Dua kelompok besar SALBP: SALBP-I, meminimalkan jumlah stasiun kerja

yang dibutuhkan untuk memenuhikebutuhan kapasitas produksi denganmempertimbangkan precedence constraints,

SALBP-II, mengalokasikan elemen-elemenkerja ke dalam stasiun-stasiun kerja yang

jumlahnya telah ditentukan untukmemaksimumkan kapasitas produksi danmempertimbangkan precedence constraints(Hackman et al. 1989).


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Scheduling High-Volume-

Low-Variety Operations The mass consumption patterns of modern industrialized

nations depend on assembly line technology. The classic example is Henry Fords auto chassis line.

Before the moving assembly line was introduced in 1913, each

chassis was assembled by one worker and required 12.5 hours. Once the new technology was installed, this time was reduced to

93 minutes.

Favorable Conditions Volume adequate for reasonable equipment utilization. Reasonably stable product demand.

Product standardization Part interchange-ability. Continuous supply of material Not all of the above must be met in every case.


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Concepts (1/2)

Minimum rational work element Smallest feasible division of work.

Flow time = time to complete all stations

Cycle time Maximum time spent at any one workstation. Largest workstation time or work element. How often a product is completed. Inverse of the desired hourly output rate = the amount of

time available at each work station to complete all assignedwork (targeting)

1 2 3

4 min 5 min 4 min

Flow time = 4 + 5 + 4 = 13

Cycle time = max (4, 5, 4) = 5


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Concepts (2/2)

Total work content: Sum of the task timesfor all the assembly tasks for the product.

Precedence diagram: network showingorder of tasks and restrictions on theirperformance

Measure of efficiency

(Tc)timeCyclex)(NworkstationsofnumberActual

( Tei)timestaskofSum=Efficiency


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Measuring the Balance Delay

Balance delay=d= %100)(

)( xNxTc

TeNxTc i

Where : N = number of work station

Tc = cycle time (largest time of work station)

Tei = time for work element i


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The Problem

Assign tasks to work stationsobserving balancing restrictions so as

to minimize balance delay whilekeeping station work content for everystation cycle time.

Restrictions: Technological: precedence requirement.

Position restrictions.


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Finding a Solution

Heuristic procedures generally allow for a broaderproblem definition, but do not guarantee optimalsolution.

Optimizing procedures generally have used morenarrowly defined problems, but guarantee optimalsolution.

Examples of optimizing procedures Dynamic programming

0-1 Integer programming Branch and bound techniques.

Trend in research has been toward optimizingprocedures due to availability of large-scalecomputers.


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Basic Production Layout

Formats Process Layout

Product Layout

Group Technology (Cellular) Layout

Fixed-Position Layout


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Process-Oriented Layout

Design places departments with large flows ofmaterial or people together

Dept. areas have similar processes

Used with process-focused processes

Examples


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Process-Oriented Layout

Floor Plan

Table Saws

Tool RoomDrill Presses

Office


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Product-Oriented Layout

Facility organized around product

Design minimizes line imbalance

Types: Fabrication line; assembly line

Examples


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Product-Oriented Layout

Floor Plan1

2

4

5

Office

Belt

Conveyor

Operations


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Cellular Layout - GroupTechnology

(Work Cells) Special case of process-oriented layout

Consists ofdifferentmachines brought

together to make a product


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Work Cell Floor Plan

Office

Tool RoomWork Cell

Saws Drills


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Fixed-Position Layout Design is for stationary project

Workers & equipment come to site

Complicating factors

Limited space at site Changing material needs

Examples Ship building

Highway construction


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Fixed Position Layout

Question: What are our primaryconsiderations for a fixed position layout?


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METHODS OF LINE

BALANCINGThe methods are heuristic approaches,

meaning that they are based on logic and

common sense rather than onmathematical proof.

The manual methods to be presented are:

1. Largest-candidate rule

2. Kilbridge and Westers method

3. Ranked positional weights method


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Method 1 : Largest-

Candidate RuleThis is the easiest method to understand.

Procedure:

Step 1. list all elements in descending order of Te

value, largest Te at the top of the list.Step 2. to assign elements to the first workstation,

start at the top of the list and work down, selectingthe first feasible element for placement at the

station. A feasible element is one that satisfies theprecedence requirements and does not cause thesum of the Te values at the station to exceed thecycle time Tc.


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Continued Largest

Candidate RuleStep 3. Continue the process of

assigning work elements to the station

as in step 2 until no further elementscan be added without exceeding Tc.

Step 4. Repeat steps 2 and 3 for the

other stations in the line until all theelements have been assigned.


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Table 1 Work elements arranged according to Te value.

no element description Te (min) Immediate predecessors

1 place frame on workholder and clamp 0.2 none

2 assemble plug, grommet to power cord 0.4 none

3 assemble brackets to frame 0.7 1

4 wire power cord to motor 0.1 1,2

5 wire power cord to switch 0.3 2

6 assemble mechanism plate to bracket 0.11 3

7 assemble blade to bracket 0.32 3

8 assemble motor to brackets 0.6 3,4

9 align blade and attach to motor 0.27 6,7,8

10 assemble switch to motor bracket 0.38 5,8

11 attach cover, inspect, and test 0.5 9,10

12 place in tote pan for packing 0.12 11


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Table 2 Work elements arranged according to Te value for the LargestCandidate Rule

no element Te (min) Immediate predecessors

3 0.7 1

8 0.6 3,4

11 0.5 9,10

2 0.4 none

10 0.38 5,8

7 0.32 3

5 0.3 2

9 0.27 6,7,8

1 0.2 none

12 0.12 11

6 0.11 3

4 0.1 1,2


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Table 3 Work elements arranged according to the LargestCandidate Rule

station element Te (min)

1

2 0.4

15 0.3

1 0.2

4 0.1

23 0.7

0.816 0.11

38 0.6

0.9810 0.38

47 0.32

0.599 0.27

511 0.5

0.6212 0.11

Te at station


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PERFORMANCE

MEASUREMENT%202.0

)0.1(5

4)0.1(5

dayBalancedel

Elements 2, 5, 1, 4 Elements 3, 6 Elements 8,10

Elements 11,12 Elements 7,9

Workflow


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Method 2 : Kilbridge and

Westers MethodStep 1. construct the precedence diagram so that

nodes representing work elements of identicalprecedence are arranged vertically in columns.

Step 2. list the elements in order of their columns,column I at the top of the list. If an element can belocated in more than one column, list all thecolumns by the element to show the transferabilityof the element.

Step 3. to assign elements to workstations, start withthe column I elements.


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solutions

no column Te (min) sum of column Tes

1 I 0.2

2 I 0.4 0.6

3 II 0.7

4 II 0.1

5 II,III 0.3 1.1

6 III 0.11

7 III 0.32

8 III 0.6 1.03

9 IV 0.27

10 IV 0.38 0.65

11 V 0.5 0.5

12 VI 0.12 0.12

Table 4 Work elements arranged according to columns in the Kilbridge and Wester

Method


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Table 5 work elements assigned to stations according to Kilbridge and Westers

Method


1

0.2

12 0.4

4 0.1

5 0.3

23 0.7

0.816 0.11

37 0.32

0.98

8 0.6

49 0.27

0.6510 0.38

511 0.5

0.6212 0.12

Te at station


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Method 3 : RankedPositional Weights Method

Step 1. calculate the RPW for each element bysumming the elements Te together with theTe values for all the elements that follow itin the arrow chain of the precedencediagram.

Step 2. list the elements in the order of theirRPW, largest RPW at the top of the list.

Step 3. assign elements to stations accordingto RPW, avoiding precedence constraint andtime-cycle violations.


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Table 6 Work elements arranged in order of RPW value in the Ranked Positional WeightsMethod

no RPW Te (min)

1 3.3 0.2

3 3 0.7

2 2.67 0.4

4 1.97 0.1

8 1.87 0.6

5 1.3 0.3

7 1.21 0.32

6 1 0.11

10 1 0.38

9 0.89 0.27

11 0.62 0.5

12 0.12 0.12


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Table 7 Work elements assigned to stations according to the Ranked Positional WeightsMethod


11 0.2

0.9

3 0.7

2

2 0.4

0.914 0.1

5 0.3

6 0.11

38 0.6

0.927 0.32

410 0.38

0.659 0.27

511 0.5

0.6212 0.12

Te at station


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Exercise of Line Balancing

Youve just been assigned the job asetting up an electric fan assembly line

with the following tasks:Task Time (Mins) Description Predecessors

A 2 Assemble frame None

B 2 Mount switch A

C 3.25 Assemble motor housing NoneD 1.2 Mount motor housing in frame A, C

E 0.5 Attach blade D

F 1.1 Assemble and attach safety grill E

G 1 Attach cord B

H 1.4 Test F, G


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Task Predecessors

A None

A

B A

B

C None

C

D A, C

D

Task Predecessors

E D

E

F E

F

G B

G

H F, G

H

PRECEDENCE DIAGRAM


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The question?

Suppose we only have demand for 100fans per day.

a.What would our cycle time have tobe?

b.How many work stations required?


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[1] Groover, Mikell P., Automation,Production Systems, And Computer

Integrated Manufacturing, Prentice-Hall,Inc, Englewood Cliffs, New Jersey, 1987.

[2] Lesmana, Hartono, Model OptimasiPenyeimbangan Lini Perakitan Dengan

Mempertimbangkan Performansi Operator,Prosiding Seminar Sistem Produksi VIYogyakarta, 14-15 Agustus 2003.

References and

acknowledgements.

materi # 14 - line balancing-1(2)

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