24 1 20 4 20 5
24 2 16 6
16 3 20 7
The decision problem of optimally partitioning (balancing) the assembly operations among the workstations with respects to some objectives is known as the assembly line balancing (ALB) problems.

Precedence diagram: network showing restrictions on the sequence of each task.

Measure of efficiency
Efficiency =
Materials & parts
生产计划与控制实践课
sum of operation times for each task (t j ) actual number of workstations ( m) ×cycle time (c)
西安交通大学 管理学院
第一讲 装配线平衡问题及其求解
授课教师：高杰 西安交通大学 管理学院 工业工程系 7/29/2010
Outlines
1. Product/Process Matrix
2. Introduction to assembly line and the balancing problem 3. Heuristic approaches for sALB problems 4. Mathematical model for sLAB-2 problems
The cycle time is defined as the time between the entering of two consecutive product units in the assembly. The cycle time is equal to the assembly time of the workstation, which holds the maximum assembly time. How often a product is completed.
constraints between tasks are to be considered.
Input
S1
1
S2
2
S3
3
S4
4
S5
5
S6
6
Output
Legend:
Si
Workstation i
j Operator
j
生产计划与控制实践课
西安交通大学
管理学院
7/29/2010
10
2 Introduction to ALB Problems uALB
生产计划与控制实践课
西安交通大学
管理学院
7/29/2010
9
2 Introduction to ALB Problems sALB
The simple assembly line balancing (sALB) problem is relevant for
the straight single product assembly lines where only precedence
The U-line balancing problem (uALB) problem considers the case of U-shaped (single product) assembly lines.
Product A Front side In Product B station 2 Product C station 5
batch model line
More than one kind of products can be made through a batch model line. Yet, shifting from manufacturing one kind of products to another incurs a certain setup cost. Therefore, products of the same kinds are made in batch rather than by individual ones.
single model line
In
batch model line
1
2
3
4
N
Out
In
1
2
3
4
N
Out
mixed model line
In
生产计划与控制实践课
1
2
3
4
N
Out
7/29/2010 8
西安交通大学
管理学院
2. Introduction to Assembly Line Balancing (ALB) Problems
生产计划与控制实践课
2 Introduction to ALB Problems
Assembly lines are still typical in the industrial production of high quantity standardized commodities
Before the “moving assembly line” was introduced in 1913, each chassis was assembled by one worker and required 12.5 hours. Once Henry Ford’s auto chassis line was installed, this time was reduced to 93 minutes.
regarding the cycle time.
生产计划与控制实践课
西安交通大学
管理学院
7ion to ALB Problems
Key concepts in the ALB problems
Flow time: the sum of operation times for each task, which is involved in the production of a product Cycle time
生产计划与控制实践课 西安交通大学 管理学院 7/29/2010 2
Product/Process Matrix
Low Volume Low Standardization
Jumbled Flow (job shop) Commercial Printer High Volume Multiple Products Few Products Low Volume Higher Volume High Standardization Void
station 1
section station 3
station 4
Out Back side
生产计划与控制实践课 西安交通大学 管理学院 7/29/2010 11
2 Introduction to ALB Problems
mALB
Mixed model assembly lines produce several models of a basic product in an intermixed sequence. Besides the mixed model assembly balancing (mALB) problems, which have to assign tasks to workstations considering the different operation times for the different models, the mixed model sequencing problem (MSP) is relevant. MSP has to find a sequencing of all model units to be produced, such that inefficiencies are minimized. mixed model line
mixed model line
More than one kinds of products can be made through a mixed model line. Adjusting the mixed model line from manufacturing one kind of products to manufacturing another kind does not involve setup cost, or only negligible cost. Generally, in order to balance the workloads of different workstations, a careful scheduling (generally FSP) is necessary, by taking the advantage of the diverse operation time of different products on the same workstations.

They even gain importance in low volume production of customized products.
Fig. 1 Example of assembly line
生产计划与控制实践课 西安交通大学 管理学院 7/29/2010 4
2 Introduction to ALB Problems Assembly lines are flow-oriented production systems.