79971255 assembly-line-balancing

ASSEMBLY LINE BALANCING - BY MAXIMUM FOLLOWERS METHOD

1. Assembly-Line Balancing:Assembly-Line Balancing:
A Valuable Tool forA Valuable Tool for
Increasing EfficiencyIncreasing Efficiency
By :
Joseph George Konnully

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Coverage
1.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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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.

4. 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

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How Can Assembly-Line Balancing Help
Organization?
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 variation
Restrict one piece flow
Maximizes Idle time
Poor efficiency
 !? Zzz Zzz
Overproduction!
Generates waste
Undesirable waiting
10 sec
40 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 variation
Increased Efficiency
Minimizes Idle time
   
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 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

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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.

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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.

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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

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Example of Assembly-Line Balancing Cont.
1. List the sequential relationships among tasks and then
draw a precedence diagram.
Tasks Tasks that
must precede
Tasks Tasks that
must precede
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

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Example of Assembly-Line Balancing Cont.
1. List the sequential relationships among tasks and
then 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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Example of Assembly-Line Balancing Cont.
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

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Example of Assembly-Line Balancing Cont.

3. Calculate the theoretical minimum number of
workstations.
Sum Total
of Task Times 250 seconds
Number of = = = 3.97 = 4 (rounded up)
workstations Cycle Time 60 seconds

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Example of Assembly-Line Balancing Cont.
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.
Task
Number of
Following Tasks
A 6
B or D 5
C or E 4
F, G, H, or I 2
J 1
K 0

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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.
Example of Assembly-Line Balancing Cont.

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Example of Assembly-Line Balancing Cont.
5 & 6. Balance made according to the Largest-Number-of-Following
Tasks Rule.
StationsTaskTask Time
(in seconds)
Number of
Following
Tasks
Remaining
Unassigned
Time
Feasible
Remaining
Tasks
Task with
Most
Followers
Task with
Longest
Operating
Time
Station 1A 50 6 10 idle None
Station 2D 55 5 5 idle None
Station 3B
E
C
16
20
14
5
4
4
44
24
10 idle
C, E
C, H, I
None
C, E
C
E
Station 4F
G
H
17
17
17
2
2
2
43
26
9 idle
G, H, I
H, I, J
None
G, H, I
H, I
G, H, or I
H or I
Station 5I
J
K
17
13
14
2
1
0
43
30
16 idle
J
K
None

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Example of Assembly-Line Balancing Cont.
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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Example of Assembly-Line Balancing Cont.
7. Evaluate the efficiency of the line balance.
Sum Total
of Task Times 250
Efficiency = = = 0.83 or 83%
Actual Number (5)(60)
of Workstations
X Cycle Time

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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.

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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.

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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.

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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.

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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.

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Thank you