Reconfiguration of assembly lines under the influence of high product variety in the automotive industry–a decision support system

Abstract

In this paper we consider the mixed model assembly line reconfiguration problem in the context of auto production which is characterised by a make-to-order production process and a huge product variety. Starting from a given line balancing solution the goal is to minimise production costs in the short term for a largely known production program by reassigning and shifting tasks between workstations. We present a mathematical optimisation model that aims at minimising the costs incurred by overload situations, regular workers and reconfiguration measures. Due to the model's complexity, lack of data and acceptance issues it is hardly possible to fully automate the solution process in an industrial environment. Therefore, we present a decision support approach that consists of visualisation components, new numerical indicators and an integrated heuristic optimisation procedure to semi-automate the reconfiguration process. In particular, reconfiguration costs can be taken into account and no complete precedence graph is required. Finally, we show on the basis of two industrial case studies that our approach can be successfully applied in a practical environment where it was capable of drastically reducing the occurrence of overload situations.

Keywords:

• assembly
• line balancing
• sequencing
• production management

Notes

Notes

1. In a practical scenario, so-called two-cycle workers, being assigned to the same workplace, would alternately take a workpiece and work on it for two cycles. This implies that these workers have to drift into the succeeding station. Becker and Scholl (2009) call this type of workplace a multiple-station workplace.

2. See also Hotman (2006, p. 31) and Smith (1998, p. 6).

3. This is comparable to the ‘Issue Detection’ process defined by Smith (1998, S. 44) and the process of analysis of Turban and Aronson (1998)

4. This is a necessary but not a sufficient condition. Further conditions are given by the precedence graph, the ratio between the costs for the shifting operations and the costs for workers that can be saved.

5. This usually minimises the costs for retraining the workers as well, as most workers are also able to do the tasks of neighbouring workplaces.

6. There may be identical solutions in the search tree because of different shift sequences.

7. See also Section 5.2.2.