79971255 assembly-line-balancing

Assembly-Line Balancing:Assembly-Line Balancing:A Valuable Tool forA Valuable Tool for

Increasing EfficiencyIncreasing Efficiency

By :

Joseph George Konnully

rcsaini.blogspot.com 2

Coverage1. What is assembly-line balancing?2. History – 1st 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.


What is assembly-line balancing?

Assigning each task to a workstation within an assembly line in order to meet the required production rate and to achieve a minimum amount of idle time.

Line balancing is the procedure in which tasks along the assembly line are assigned to work station so each has approximately same amount of work.

Ford installs first moving assembly line 1913

In 1907, Henry Ford announced his goal for the Ford Motor Company: to create "a motor car for the great multitude." At that time, automobiles were expensive, custom-made machines.

Ford's engineers took the first step towards this goal by designing the Model T, a simple, sturdy car, offering no factory options -- not even a choice of color. The Model T, first produced in 1908, kept the same design until the last one -- number 15,000,000 -- rolled off the line in 1927. From the start, the Model T was less expensive than most other cars, but it was still not attainable for the "multitude."

Photo: Moving assembly line at Ford Motor Company's Michigan plant

History


How Can Assembly-Line Balancing HelpOrganization?

Increased efficiency

Increased productivity

Potential increase in profits and decrease in costs


Unbalance Line and Its effect

High work load in some stages (Overburden) Maximizes wastes (over-processing, inventory, waiting, rework, transportation,

motion) High variation Restrict one piece flow Maximizes Idle time Poor 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


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 variation Increased Efficiency Minimizes Idle time

Work Station 1

Work Station 4

Work Station 3

Work Station 2

25 sec 25 sec 20 sec 15 sec


Steps in Balancing an Assembly Line

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

2. Calculate the required workstation cycle time.

3. Calculate the theoretical minimum number of workstations.

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

. . . more


Steps in Balancing an Assembly Line Cont.

5. Beginning with the first workstation, assign each task, one at a time, until the sum of the task times is equal to the workstation cycle time or until no other tasks can be assigned due to sequence or time restrictions.

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.


Example of Assembly-Line Balancing

Problem: The Model Z Bicycle is assembled in an assembly line. Four hundred bicycles are required each day. Production time per day is 420 minutes.

Find the balance that minimizes the number of workstations, that stays within the workstation cycle time limitation, and that complies with task

precedent constraints.


Example of Assembly-Line Balancing Cont.

1. Building the Model Z Bicycle: Assembly Steps and Times

Task 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




Tasks Tasks that must precede



A — E D I E

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

C B G C K J

D — H E




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



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. 25,200

Cycle = = = = 60 sec. Time Output per day 420 bicycles 420


Example of Assembly-Line Balancing Cont. 3. Calculate the theoretical minimum number of workstations.

Sum Total of Task Times 250 secondsNumber of = = = 3.97 = 4 (rounded up)workstations Cycle Time 60 seconds



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

For this example, our primary rule is to prioritize tasks based on the largest number of following tasks.

If there is a tie, our secondary rule is to prioritize tasks in the order of the longest task time.

In general, select rules that prioritize tasks according to the largest number of followers or based on length of time.

TaskNumber of Following Tasks

A 6

B or D 5

C or E 4

F, G, H, or I 2

J 1

K 0


5. Beginning with the first workstation, assign each task, one at a time, until the sum of the task times is equal to the workstation cycle time or until no other tasks can be assigned due to sequence or time restrictions.

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




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

Stations Task Task Time(in seconds)

Number ofFollowing Tasks

RemainingUnassignedTime

FeasibleRemainingTasks

Task withMostFollowers

Task withLongestOperatingTime

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, INone

C, EC

E

Station 4 FGH

171717

222

43269 idle

G, H, IH, I, JNone

G, H, IH, I

G, H, or IH or I

Station 5 IJK

171314

210

433016 idle

JK None



5 & 6. Precedence Graph for Model Z Bicycle.

The five workstations are identified by color.

14 sec.

H

G55 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



7. Evaluate the efficiency of the line balance.

Sum Total of Task Times 250Efficiency = = = 0.83 or 83%

Actual Number (5)(60) of Workstations X Cycle Time


Assembly-Line Balancing in the real world

The simple ALB problem approach is limited by some constraints:

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 the

same workstation.


Assembly-Line Balancing in the real world(cont.)

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

for one task.

Multiple Products. Coping with different products, some operations are needed for

some 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 with

some degree of incapacity.


Assembly-Line Balancing by Digital Manufacturing

Build AL in virtual environment.Put Input data e.g. No.Assembly part, Task at each

station and estimated time, Human ergonomics etc.Run the Virtual AL and find outcome.Make changes in AL in virtual world and find best

ALB outcome.Build in real world.


Assembly-Line Balancing by Digital Manufacturing Cont.

Advantages

Time Saving.Money Saving (Time Is Money, make changes in

virtual world).Simplifies complex assembly line balancing

problems.Faster, easier, and more accurate than calculating

by hand.


Summary

1. Assembly-Line Balancing consists of assigning each task to a workstation to meet the required production rate and to achieve 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, the theoretical minimum number of workstations, workstation assignments, and assembly line efficiency.

4. Digital Manufacturing Simplifies complex assembly line balancing problems with faster, easier, and more accurate than calculating by hand and its save time & money.


Thank you

79971255 assembly-line-balancing

Documents

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