1. Assembly-line balancing is the process of assigning tasks to workstations along an assembly line to maximize efficiency. 2. It aims to balance the workload across stations so that no station is a bottleneck and idle time is minimized. 3. The document provides steps for balancing an assembly line, including determining task relationships, cycle time, number of stations, and assigning tasks based on precedence and time constraints. It includes an example to illustrate the process.

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

2. Coverage
1. 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.
rcsaini.blogspot.com 2

3. 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.
rcsaini.blogspot.com 3

4. History
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

5. How Can Assembly-Line Balancing Help
Organization?
 Increased efficiency
 Increased productivity
 Potential increase in profits and decrease in costs
rcsaini.blogspot.com 5

6. Unbalance Line and Its effect
 !? Zzz Zzz
10 sec
40 sec 15 sec 15 sec
Overproduction! Undesirable waiting
Generates waste
 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 rcsaini.blogspot.com 6
 Poor efficiency

7. Balanced Line and its effect
   
25 sec 25 sec 20 sec 15 sec
 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
rcsaini.blogspot.com 7
 Minimizes Idle time

8. 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
rcsaini.blogspot.com 8

9. 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.
rcsaini.blogspot.com 9

10. 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.
rcsaini.blogspot.com 10

11. Example of Assembly-Line Balancing Cont.
1. Building the Model Z Bicycle: Assembly Steps and Times
Task Task Time Task Description Tasks that
(in seconds) 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 rcsaini.blogspot.com 11

12. Example of Assembly-Line Balancing Cont.
1. List the sequential relationships among tasks and then
draw a precedence diagram.
Tasks Tasks that Tasks Tasks that Tasks Tasks that
must precede must precede 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
rcsaini.blogspot.com 12

13. Example of Assembly-Line Balancing Cont.
1. List the sequential relationships among tasks and
then draw a precedence diagram.
50 sec. 16 sec. 14 sec. 17 sec.
A B C F
17 sec.
13 sec. 14 sec.
17 sec.
G
55 sec. 20 sec.
J K
H
D E
17 sec.
I
rcsaini.blogspot.com 13

14. 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
rcsaini.blogspot.com 14

15. 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
rcsaini.blogspot.com 15

16. 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 Number of
rule is to prioritize tasks based Task Following Tasks
on the largest number of
following tasks. A 6
 If there is a tie, our secondary B or D 5
rule is to prioritize tasks in the
C or E 4
order of the longest task time.
 In general, select rules that F, G, H, or I 2
prioritize tasks according to J 1
the largest number of
followers or based on length
rcsaini.blogspot.com
K 0
16
of time.

17. Example of Assembly-Line Balancing 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.
rcsaini.blogspot.com 17

18. Example of Assembly-Line Balancing Cont.
5 & 6. Balance made according to the Largest-Number-of-Following
Tasks Rule.
Stations Task Task Time Number of Remaining Feasible Task with Task with
(in seconds) Following Unassigned Remaining Most Longest
Tasks Time Tasks Followers Operating
Time
Station 1 A 50 6 10 idle None
Station 2 D 55 5 5 idle None
Station 3 B 16 5 44 C, E C, E E
E 20 4 24 C, H, I C
C 14 4 10 idle None
Station 4 F 17 2 43 G, H, I G, H, I G, H, or I
G 17 2 26 H, I, J H, I H or I
H 17 2 9 idle None
Station 5 I 17 2 43 J
J 13 1 30 K
K 14 0 16 idle None
rcsaini.blogspot.com 18

19. Example of Assembly-Line Balancing Cont.
5 & 6. Precedence Graph for Model Z Bicycle.
The five workstations are identified by color.
50 sec. 16 sec. 14 sec. 17 sec.
A B C F
17 sec.
13 sec. 14 sec.
17 sec.
G
55 sec. 20 sec.
J K
H
D E
17 sec.
I
rcsaini.blogspot.com 19

20. 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
rcsaini.blogspot.com 20

21. 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.
rcsaini.blogspot.com 21

22. 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.
rcsaini.blogspot.com 22

23. 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.
rcsaini.blogspot.com 23

24. 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.
rcsaini.blogspot.com 24

25. 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.
rcsaini.blogspot.com 25

26. Thank you
rcsaini.blogspot.com 26