Reaches On The Constructing And Scheduling Of Virtual Cells Based On Queuing Network

With the advent of the era of customers personalized and diversified consumption, enterprises are faced with the chanllenge of the increasing demand for products category, the continuous improvement of customer personalized requirements, the constant shorten of product delivery time, high quality with low cost and so on. Manufacturing enterprises mainly focus on how to adapt to the change of market and response to customer demand in short time. Virtual cells are the further development of cellular manufacturing production applied in manufacturing enterprises. With the application of virtual cellular production, manufacturing enterprises can fully exploit potentialities with less time and capital investment, which can effectively avoid the reset cost of machine physical layouts change and enhance the market competitiveness of enterprises. Virtual cellular production can improve the production efficiency and the adaptability of the workshop production line to the diversification of product demand, and furtherly short the production cycle of products. However, considering the randomness arrival of workpieces and the uncertainty of workpieces operating on machines, there is often a queue phenomenon of workpieces waiting for processing in virtual cellular manufacturing system, which results in the high congestion rate of the system, affects the improvement of production efficiency and flexiblility of virtual cellular manufacturing system and prolongs the production time and cycle of workpieces. In view of this, the article mainly focuses on the effect of waiting time factor in virtual cellular construction and scheduling, and studies how to design the virtual cellular constructing strategy and scheduling scheme to eliminate the queuing phenomenon in virtual cellular manufacturing system, which is beneficial to shortening production cycle and responsing to customer demand rapidly.Cellular construction is a primary problem to ensure the balance of production load in virtual cellular manufacturing system and organize the production of virtual cells.Faced with the flexibility of routing problem in manufacturing cells caused by the plurality of same processing capacity of equipments, the article proposes the virtual cellular construction model based on Queuing Network theory. The article takes the waiting time of workpieces as the starting point and expresses the concept of the total flow time in vrtual cells, and uses Queuing Network theory to calculate the waiting time and other performance indicators of the parts. Based on this, the article takes the flow time of parts operating on machines as the path weight, and constructs the constructing path diagram of virtual cells based on queuing network. And based on the virtual cellular construction network chart, the paper solves the virtual cellular constructing model considering waiting time with the Double-Sweep algorithm solving the problem of the shortest path problem.Each workpiece of oarts family has an optimal path, and the article determine the number of shared machines through WITNESS simulation. Applied in the example, the results show that optimal paths of each part in virtual cells are both feasible and effective.The article can determine the number and type of machines in virtual cells using Queuing Network method, and construct virtual manufacturing cells.Based on the completion of virtual cell construction,the article considers the equipment resource and other factors comprehensively,and proposesthe scheduling model with the target of minimizing the total flow time.Part families produced in virtual manufacturing cells have many parts,and each part has one or more processes,which can operate on a plurality of machines with the same function. The article selects the appropriate machines for each process, and determines the processing sequence and strating time of each process.The article solves the model with the hybird algorithm of Genetic algorithm and Ant colony algorithm.The hybrid algorithm combines the advantages of Genetic algorithm and Ant colony algorithm, which avoids the problem that Genetic algorithm easily falls into local optimum faced with complex problems.That can obtain the satisfactory scheduling scheme. Through the example, the results show that the scheduling scheme effectively shorten the total flow time in virtual cellular manufacturing system,which reach a state satisfying the overall goal of the production system.In order to verify the operation effect of the proposed virtual cellular constructing and scheduling model in actual enterprises, this paper analyzes the the product status and problems of GSI shipyard, and apply the proposed concept into the pipe processing workshops in the shipyard, which reduces queuing and congestion, and optimize the allocation of resources in the process of constructing and scheduling. By the comparison of actual production in enterprises adopting the proposed model before and after, the results prove the feasibility and effectiveness of the proposed method and theory in the paper.