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Different production capacities can be achieved by different reconfigurations of machining devices. For example, through different compositions of T (translation) and R (rotation), and whether or not R and T were out of the side of cutters or work pieces of movement chain, different configurations of machine tool can be obtained which can adapt to different machining operations. It means the optimal production efficiency and benefits can be obtained by selecting the optimal configuration of machine tool according to part process plan. Of course, to choose different configurations of machine tools according to the process plan has also a lot of limitations. High demand of machining capacity usually leads to higher production cost and reconfiguration cost. Meanwhile, configurations of machine tools also affect manufacturing quality of parts. For the above reasons, the optimization method based on cooperative consideration of process plan design and configurations of machine tool according to part process features is presented in the paper. The extraction and analysis of part process plan is a very complex problem, in addition, the machine tool reconfiguration is a multi-factors consideration problem, so the above problem is a Non-deterministic Polynomial problem. Using genetic algorithm (GA) to solve optimization problem can obtain an optimal/suboptimal solution in relatively rapid rate. The paper is organized as follows: section 2 details the problems; section 3 defines the problem model; section 4 presents the optimization method based on GA; section 5 discusses an actual case; the conclusion is presented in section 6.
2 Problem Statement
The cooperative optimization model based on production process plan and configurations of machine tool needs consider the following problems: how to choose configurations of machine tool, operation precedence based production process plan, line balance, arrangements for production process and so on.
2.1 Operation process design of part production
In order to achieve rapid response to market demand, the part design uses the modular design approach. During the process of decomposition and classification of structural module characteristics, some variant designs are carried out at the same time, which makes that products have both consistency and personalization. For this kind of products, the process design and plan are described as follows. According to structural characters of parts, the n-dimension features are decomposed, and the implementation of each character needs a series of operation processes (OPs) The processes are shown by the directed graph in Fig. 2. Fig. 2. Directed graph of operation precedence 12 ,,,nFFFi F12 , ,, . mOPOPOPEach OP can be processed in different ways. For example, the complement of half precision production of hole can adopt the mode: bore, expand or hinge. The directed links show the sequential relationship between processes
2.2 Production line design
The line design includes line balance, choice of productive resources, and layout of machine tools, logistics design and other issues. In the paper, the focus is on the configuration and reconfiguration choice of machine tools and the balance of cycle time. A reconfigurable production line usually consists of several RMTs, as well as buffers, transportation equipment, process aid components, and so on. Each RMT has a certain degree of transformation ability to adapt to a range of process requirements. Non-reconfigurable production lines attach great importance to cycle time, bottleneck, the largest production capacity and other factors. However, reconfigurable production lines consider not only the above indicators but also the reconfiguration cost. The production cycle balancing of each station in production line is an important issue for production line design. Hence, one of the important goals in production line design is to distribute the workload as evenly as possible. One of the characteristics of RMTs is that it can have different functions and capacity by different reconfiguration actions, such as adding/removing components. The changes of configurations usually lead to reconfiguration cost, and each specific configuration needs some amount of cost. Generally, the production cost of product is a fixed value according to configuration of machine tool which means that the production time and cost of some operation is mainly dependent on the selection of configuration of machine tools.