第一讲装配线平衡问题及其求解

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

Measure of efficiency
Efficiency =
Materials & parts
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sum of operation times for each task (t j ) actual number of workstations ( m) ×cycle time (c)
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
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2 Introduction to ALB Problems uALB
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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
station 1
section station 3
station 4
Out Back side
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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

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.
Disconnected Line Flow (batch)
Heavy Equipment Auto Assembly
Connected Line Flow (assembly batch)
Continuous Flow
Void
Sugar Refinery
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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.
2 3 4 min
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1 4 min
5 min
Product s
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flow time = 4 + 5 + 4 = 13 cycle time = max {4, 5, 4} = 5
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2 Introduction to ALB Problems
Table 1 Precedence structure i 1 1 2 3 4 5 6 7 8 9 j 2 6 3 8 5 6 7 8 9 10 Table 2 Operation time Task j Operation time tj 1 24 2 24 3 16 4 20 5 20 6 16 7 20 8 8 9 36 10 8
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
single model line
In
batch model line
1
2
3
4
N
Out
In
1
2
3
4
N
Out
mixed model line
In
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1
2
3
4
N
Out
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2. Introduction to Assembly Line Balancing (ALB) Problems
Materials & parts
1
2
3
4
5
Product s
An assembly line consists of a certain number of workstations, which are arranged along a conveyor belt. The workpieces are consecutively launched down the line and are moved from workstation to workstation. At each workstation, certain tasks are repeatedly performed
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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
regarding the cycle time.
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2 Introduction 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
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.
36 9 8 10
8 8
Fig. 2 Example of precedence diagram
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2. Introduction to Assembly Line Balancing (ALB) Problems
With respects to the possible products manufactured by an assembly line, there are three basic kinds of assembly lines.
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.
single model line
Only one kind of products can be made through a single model line, i.e., each assembly line is dedicated to only one kind of product.
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.
The U-line balancing problem (uALB) problem considers the case of U-shaped (single product) assembly lines.
ProduLeabharlann Baidut 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.