The document explains assembly line balancing (ALB), which is the process of assigning tasks to workstations while respecting precedence relations, ensuring cycle time is not exceeded, and minimizing idle time. It discusses concepts like cycle time, theoretical number of workstations, balance delay, and various types of ALB problems focused on efficiency and workload balance. An example illustrates these principles with a case for assembling electric fans, detailing tasks, times, and daily production requirements.

1. Assembly line
balancing
INTRODUCTION

2. Definition of assembly lines
 Assembly line is a sequence of work stations performing a specified
repeated tasks on a product units moving along the line at constant speed.
 Each unit of the product spends the same amount of time in every station,
this time is called cycle time.
 The sequence, in which operations must be performed, follow certain
constraints called precedence relations.

3. Assembly line balancing (ALB)
 It is the procedure concerning the assignment of tasks to work stations so
that:
• Precedence relations are respected.
• Workstation time do not exceed the cycl time.
• Minimize the total idle time.

4. Important relations
 Cycle time (C) =
𝐴𝑣𝑎𝑖𝑙𝑎𝑏𝑙𝑒 𝑤𝑜𝑟𝑘𝑖𝑛𝑔 𝑡𝑖𝑚𝑒
𝐶𝑢𝑠𝑡𝑜𝑚𝑒𝑟 𝑑𝑒𝑚𝑎𝑛𝑑 𝑜𝑟 𝑡ℎ𝑒 𝑑𝑒𝑠𝑖𝑟𝑒𝑑 𝑝𝑟𝑜𝑑𝑢𝑐𝑡𝑖𝑜𝑛
 Theoretical number of work stations (N)=
𝑆𝑢𝑚𝑚𝑎𝑡𝑖𝑜𝑛 𝑜𝑓 𝑡𝑎𝑠𝑘 𝑡𝑖𝑚𝑒𝑠
𝑐𝑦𝑐𝑙𝑒 𝑡𝑖𝑚𝑒
 Theoretical line efficiency =
𝑆𝑢𝑚𝑚𝑎𝑡𝑖𝑜𝑛 𝑜𝑓 𝑡𝑎𝑠𝑘 𝑡𝑖𝑚𝑒𝑠
𝑁∗𝐶
%
 Balance delay (BD) =1-Efficiency.
 Smoothing index (SI)= (𝑀𝑎𝑥𝑖𝑚𝑢𝑚 𝑠𝑡𝑎𝑡𝑖𝑜𝑛 𝑡𝑖𝑚𝑒 − 𝑠𝑡𝑎𝑡𝑖𝑜𝑛 𝑡𝑖𝑚𝑒)
2
 SI is preferred to be small and near zero. This indicates a perfect workload
balance.

5. Goals of ALB
 The ALB problem can be classified to different types according to the
objective as the following:
• Type-1: minimizing the total number of stations.
• Type-2: minimize the number of work stations.
• Type-3: maximize the work load balance.
• Type-E: this type is concerned with maximizing the efficiency of assembly
line by minimizing cycle time and number of stations.

6. Example
 The example below shows the tasks required for assembly of electric fan
and the time of each task and the precedence relations between tasks.
Code task time
A Assemble frame 3
B Mount switch 1
C Assemble motor housing 3.25
D Mount motor housing in frame 1.2
E Attach blade 0.5
F Assemble and attach safety grill 1
G Attach cord 1
H Test 1.4
A
C
B
D E F
G
H
2
3.25
1
1.2 .5
1
1.4
1

7.  Daily demand 100 units per day and the available working time is 420
minutes daily.
 Required cycle time (C) =
420
100
= 4.2 minutes/ unit
 Theoretical number of work stations =
𝑆𝑢𝑚𝑚𝑎𝑡𝑖𝑜𝑛 𝑜𝑓 𝑡𝑎𝑠𝑘 𝑡𝑖𝑚𝑒𝑠
𝑐𝑦𝑐𝑙𝑒 𝑡𝑖𝑚𝑒
=
11.35
4.2
=
2.702. (round up to nearest integer number = 3).

8. Station no. Task Description Predecessors Assigned
time (min)
Remaining
time
1 A
B
G
Assemble Frame
Mount Switch
Attach Cord
-
A
B
2
1
1
2.2
1.2
0.2
2 C Assemble Motor Housing - 3.25 0.95
3 D
E
F
H
Mount motor housing in
frame
Attach Blade
Assemble and attach safety
grill
Test
A,C
D
E
F,G
1.2
0.5
1
1.4
3
2.5
1.5
0.1

9. Performance criteria of the line
 Actual cycle time (realized cycle time) =4.1
 Line efficiency =
11.35
4.1∗3
= 92.27 %
 SI= 0.98

10. Thank you