Design Product Layouts: Line
Balancing
Line Balancing is the process of assigning
tasks to workstations in such a way that
the workstations have approximately
equal time requirements.
6-1
Cycle Time
Cycle time is the maximum time
allowed at each workstation to
complete its set of tasks on a unit.
6-2
Determine Maximum Output
OT
Out put rat e =
CT
OT  operat ingt imeper day
D = Desired out put rat e
OT
CT = cycle t ime=
D
6-3
Determine the Minimum Number
of Workstations Required
N=
( t )
CT
 t = sum of t ask t ime
6-4
Precedence Diagram
Figure 6.11
Precedence diagram: Tool used in line balancing to
display elemental tasks and sequence requirements
0.1 min.
1.0 min.
a
b
c
0.7 min.
d
0.5 min.
A Simple Precedence
Diagram
e
0.2 min.
6-5
Example 1: Assembly Line
Balancing
 Arrange tasks shown in Figure 6.10
into three workstations.


Use a cycle time of 1.0 minute
Assign tasks in order of the most number
of followers
6-6
Example 1 Solution
Eligible
Revised
Assign Time
Task
Remaining
1.0
0.9
0.2
a, c
c
none
a
c
-
0.9
0.2
2
1.0
b
b
0.0
3
1.0
0.5
0.3
d
e
-
d
e
-
0.5
0.3
Time
Workstation Remaining
1
Station
Idle Time
0.2
0.0
0.3
0.5
6-7
Calculate Percent Idle Time
Idle time per cycle
Percent idle time =
(N)(CT)
Efficiency = 1 – Percent idle time
6-8
Line Balancing Rules
Some Heuristic (intuitive) Rules:
 Assign tasks in order of most following
tasks.
 Count the number of tasks that follow
 Assign tasks in order of greatest
positional weight.

Positional weight is the sum of each task’s
time and the times of all following tasks.
6-9
Example 2
0.2
0.2
0.3
a
b
e
0.8
0.6
c
d
f
g
h
1.0
0.4
0.3
6-10
Solution to Example 2
Station 1
a
b
Station 2
Station 3
e
f
c
Station 4
g
h
d
6-11
Bottleneck Workstation
1 min.
30/hr.
1 min.
30/hr.
2 min.
30/hr.
1 min.
30/hr.
Bottleneck
6-12
Parallel Workstations
30/hr.
1 min.
60/hr.
2 min.
30/hr.
1 min.
1 min.
60/hr.
30/hr.
2 min.
30/hr.
Parallel Workstations
6-13