A Research On Resequencing Methods Of Automobile Mixed-Model Assembly Lines

Product variety of automobile has steadily increased nowadays as modern technology being fast developed, market competition being fierce and customers' demands being unique. As a flexible manufacturing system which can simultaneously provide multiple product models efficiently and economically, mixed-model assembly lines (MMAL) is widespread in automobile manufacturing. And a lot of researches on MMAL sequencing problem and resequencing problem have been carried out on the purpose of further reducing manufacturing cost.This thesis focuses on resequencing problems in paint shop, and research three different ways of applying resequencing in paint shop:only applying virtual resequencing, only applying physical resequencing and applying both virtual resequencing and physical resequencing. The major work of this thesis is summarized as follow:(1) This part treats the car resequencing problem where virtual resequencing is applied to reshuffle a given initial sequence and color changes are to be minimized. The problem is formalized, greedy rules and a graph-based beam search procedure are presented and the performance is tested through computational study. Furthermore, two search procedures, iterated beam search and simulated annealing, based on beam search are presented and tested.(2) This part studies the car resequencing problem where a selectivity bank is used to reshuffle a given initial sequence, which is much larger than the capacity of selectivity bank, and color changes are to be minimized. A simulation model is established, a greedy filling method and a single color releasing method are presented and the performance is tested through simulation study. Furthermore, the simulation study shows that it is beneficial to add the number of lanes in selectivity bank and the optimal WIP level of selectivity bank is between 50%-70%.(3) This part mixes physical resequencing with virtual resequencing to reshuffle a given initial sequence, which is much larger than the capacity of selectivity bank, and color changes are to be minimized. Virtual resequencing is carried out both in upstream sequence and in selectivity bank, and a simulation model is established accordingly. A color oriented method for upstream sequence and a local search for selectivity bank are presented and the performance is tested through simulation study. Furthermore, the simulation study shows that it is beneficial to enlarge the capacity of overlap area between two adjacent shops.