Scheduling Methods Of Multi-process Reentrant Hybrid Flow Shop In Cold Rolling Stages Of Aluminum/Copper Strip And System Development

As a key process in the production of aluminum/copper strip,cold rolling plays a decisive role in the production efficiency of the enterprise.The characteristics of large scale,multi-process and multi-units make it complex to solve.The contradiction between the mass production methods of iron and steel enterprises and the individualized needs of customers’ multi-variety and small batches is more prominent,which brings great problems to the production design and production organization of aluminum/copper strip enterprises.Therefore,it is necessary to develop a cold rolling production scheduling system of aluminum/copper strip to help enterprises reduce production costs and improve production efficiency.Compared with the steel industry,there are few studies on the cold rolling scheduling of aluminum/copper strips nowadays.In steel industry,cold rolling scheduling problem is mainly treated as Travelling Salesman Problem with Time Windows(TSPTW)problem.The essences of the problem are the assignment of machine and the decision of the start time of the process of each slab,which is constrained by the time window.The process of mill assignment is similar to that in the steel industry,nevertheless,the characteristics of reentrant in the production and the annealing process of the bell furnace are similar to those of the semiconductor industry.Reentrant Hybrid Flow Shop(RHFS)is common used in solving the scheduling problem of semiconductor industry.Thus,the RHFS model is applied to the aluminum/copper strip cold rolling scheduling,and it has made good progress.The main work is as follows:(1)A mathematical model is established with the objective function of minimizing the makespan and the constrain of the aluminum/copper strip cold rolling.A small-scale case is used to verify the correctness of the model.(2)For the large-scale problem of the real factory processing,two heuristics with different time complexity based on priority scheduling method and improved NEH are designed and compared with time costs and the quality of the solutions.(3)In order to get closer to the best solution,an effective algorithm based on iteration greedy algorithm is designed and compared with local search algorithm and standard iteration greedy algorithm.The local search algorithm is easy to fall into local optimum,and the standard iteration greedy algorithm is slow in convergence.(4)The aluminum/copper strip cold rolling scheduling system is designed with all the algorithms in the paper.The users can complete the management of the factory data,the maintenance of the order data and the query of the historical solutions by simply using the mouse.