Assembly.ppt

8/14/2019 Assembly.ppt

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Assembly-Line Balancing:A Valuable Tool for

Increasing Efficiency

By :Joseph George Konnully


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rcsaini.blogspot.com 2

Coverage1. What is assembly-line balancing?2. History 1 st time introduces.3. How can assembly-line balancing be used in

organization?4. Unbalance Line and Its effect.5. Balanced Line and its effect.6. What are the steps in balancing an assembly line?7. Example of assembly-line balancing.

8. Assembly-Line Balancing in the real world.9. Assembly-Line Balancing by Digital

Manufacturing.10. Summary.

11. Suggested reading list.


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Ford installs first moving assembly line

1913

In 1907, Henry Ford announced his goalfor the Ford Motor Company: to create "amotor car for the great multitude." At thattime, automobiles were expensive,custom-made machines.

Ford's engineers took the first step towardsthis goal by designing the Model T, asimple, sturdy car, offering no factoryoptions -- not even a choice of color. TheModel T, first produced in 1908, kept thesame design until the last one -- number15,000,000 -- rolled off the line in 1927.From the start, the Model T was lessexpensive than most other cars, but it wasstill not attainable for the "multitude."

Photo: Moving assembly line at FordMotor Company's Michigan plant

History


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How Can Assembly-Line Balancing HelpOrganization?

Increased efficiency

Increased productivity

Potential increase in profits and decrease in costs


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Unbalance Line and Its effect

High work load in some stages (Overburden)Maximizes wastes (over-processing, inventory, waiting, rework, transportation,motion)High variationRestrict one piece flowMaximizes Idle timePoor efficiency

Work

Station 1

Work

Station 4

Work

Station 3

Work

Station 2

!? Zzz Zzz

Overproduction!Generates waste

Undesirable waiting

10 sec40 sec 15 sec 15 sec


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Balanced Line and its effect

Promotes one piece flow

Avoids excessive work load in some stages (overburden)Minimizes wastes (over-processing, inventory, waiting, rework,transportation, motion)Reduces variationIncreased Efficiency

Minimizes Idle time

WorkStation 1

WorkStation 4

WorkStation 3

WorkStation 2

25 sec 25 sec 20 sec 15 sec


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Steps in Balancing an Assembly Line

1. List the sequential relationships among tasks andthen draw a precedence diagram.

2. Calculate the required workstation cycle time.

3. Calculate the theoretical minimum number ofworkstations.

4. Choose a primary rule that will determine howtasks are to be assigned to workstations.

. . . more


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Steps in Balancing an Assembly Line Cont.

5. Beginning with the first workstation, assign eachtask, one at a time, until the sum of the task times isequal to the workstation cycle time or until no other

tasks can be assigned due to sequence or timerestrictions.6. Repeat step 5 for the remaining workstations until

all the tasks have been assigned to a workstation.

7. Evaluate the efficiency of the line balance.8. Rebalance if necessary.


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Example of Assembly-Line Balancing

Problem : The Model Z Bicycle is assembled in anassembly line. Four hundred bicycles are requiredeach day. Production time per day is 420 minutes.

Find the balance that minimizes the number ofworkstations, that stays within the workstation cycletime limitation, and that complies with taskprecedent constraints.


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Example of Assembly-Line Balancing Cont.

1. Building the Model Z Bicycle: Assembly Steps and TimesTask Task Time

(in seconds) Task Description Tasks that

must precede

A 50 Connect the front tire to the bicycle frame.

B 16 Insert the handle bar. A

C 14 Tighten handle bar with two screws and nuts. B

D 55 Connect the rear tire to the bicycle frame.

E 20 Position chain mechanism to the frame. D

F 17 Attach right hand brake to handle bar. C

G 17 Attach left hand brake to handle bar. C

H 17 Attach right side pedal. E

I 17 Attach left side pedal. E

J 13 Position chain onto chain mechanism. F,G,H,I

K 14 Attach seat post. J

250


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1. List the sequential relationships among tasks and thendraw a precedence diagram.

Tasks Tasks thatmust precede



A E D I E

B A F C J F,G,H,I

C B G C K J

D H E


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1. List the sequential relationships among tasks andthen draw a precedence diagram.

H

G

14 sec.

55 sec.

50 sec.

A

16 sec.

B

20 sec.

E

14 sec.

C

17 sec.

17 sec.

17 sec.

17 sec.

F

I

13 sec.

J K

D


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2. Calculate the required workstation cycle time.Convert minutes to seconds because task times are in seconds.

Production time per day 60 sec. X 420 min. 25,200Cycle = = = = 60 sec.Time Output per day 420 bicycles 420


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3. Calculate the theoretical minimum number ofworkstations.

Sum Totalof Task Times 250 seconds

Number of = = = 3.97 = 4 (rounded up)workstations Cycle Time 60 seconds


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5. Beginning with the first workstation, assign eachtask, one at a time, until the sum of the task times is

equal to the workstation cycle time or until no othertasks can be assigned due to sequence or timerestrictions.

6. Repeat step 5 for the remaining workstations until allthe tasks have been assigned to a workstation.



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5 & 6. Balance made according to the Largest-Number-of-Following

Tasks Rule.Stations Task Task Time

(i n seconds) Num ber ofFollowingTasks

RemainingUnassignedTime

FeasibleRemainingTasks

Task wi thM ostFollowers

Task wi thLongestOperatingTime

Station 1 A 50 6 10 idle None

Station 2 D 55 5 5 idle None

Station 3 BEC

162014

544

442410 idle

C, EC, H, I

None

C, EC

E

Station 4 FGH

171717

222

43269 idle

G, H, IH, I, J None

G, H, IH, I G, H, or IH or I

Station 5 IJK

171314

210

433016 idle

JK

None


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5 & 6. Precedence Graph for Model Z Bicycle.

The five workstations are identified by color.

14 sec.

H

G 55 sec.

50 sec.

A

16 sec.

B

20 sec.

E

14 sec.

C

17 sec.

17 sec.

17 sec.

17 sec.

F

I

13 sec.

J K

D


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7. Evaluate the efficiency of the line balance.

Sum Totalof Task Times 250

Efficiency = = = 0.83 or 83%

Actual Number (5)(60)of WorkstationsX Cycle Time


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Assembly-Line Balancing in the real world

The simple ALB problem approach is limited by someconstraints:Balance on existing and operating lines.

Workstations have spatial constraints.Some workstations cannot be eliminated.Need to smooth workload among workstations.

Multiple operators per workstation.Different paces among operators, different lead times within thesame workstation.


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Assembly-Line Balancing in the realworld(cont.)

Operator spatial constraints.Different workstation imposed working positions.More than one task to be performed in what should be the spacefor one task.

Multiple Products.Coping with different products, some operations are needed forsome products but not for others.Some products can introduce peak times in some workstations.

Different task times performed in different shifts.Particularly when introducing new employees or workers withsome degree of incapacity.


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Assembly-Line Balancing by DigitalManufacturing Cont.

Advantages

Time Saving.

Money Saving (Time Is Money, make changes invirtual world).Simplifies complex assembly line balancingproblems.

Faster, easier, and more accurate than calculatingby hand.


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Summary

1. Assembly-Line Balancing consists of assigning each task toa workstation to meet the required production rate and toachieve a minimum amount of idle time.

2. Benefits of line balancing includes increased efficiency and

increased productivity.3. Balance assembly line by determining sequential task

relationships, the required workstation cycle time, thetheoretical minimum number of workstations, workstationassignments, and assembly line efficiency.

4. Digital Manufacturing Simplifies complex assembly linebalancing problems with faster, easier, and more accuratethan calculating by hand and its save time & money.


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Thank you

Assembly.ppt

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