Research On Stochastic U-shaped Mixed-model Assembly Line Balancing Problems

U-shaped assembly line is the outcome of lean production. Compared to the traditional linear assembly line, U-shaped assembly line could obtain the better balancing result and save the layout space, the operators in U-shaped assembly line can get to other stand with a short distance because of the connection between the front and rear of U-shaped assembly line, so the material will be saved in transportation. U-shaped assembly line is a flexible assembly line. The cycle time of assembly line can be adjusted when demand changes. According to this character, the U-shaped assembly line was mostly used in enterprise of manufacturing for mixed model product, named U-shaped mixed model assembly line. However, there are many variable factors in the process of U-shaped mixed model assembly line, which directly limit the production efficiency of the assembly line. Therefore, how to effectively weaken or even eliminate the influence of such factors is the urgent problem for enterprises.This paper takes U-shaped mixed model assembly line as the research object, which is generally used in enterprise, and consider scheduling problem of product in the U-shaped mixed model assembly line, then research the stochastic U-shaped mixed model assembly line balancing problem. Research contents include the search of optimal task allocation and the optimal product sequencing in U-shaped mixed model assembly line balance problem, considering the complexity of two problems, this paper proposes a method consists of three steps named step-by-step method. The first step, Use the single species of the U-shaped assembly line balancing method equivalent U-shaped mixed model assembly line balancing method, and utilize the mathematical modeling and genetic algorithm to find the optimal task allocation of simplified stochastic U-shaped mixed model assembly line balancing problem. Secondly, utilize the mathematical modeling and algorithm to find several optimal sequencing scheme of stochastic U-shaped mixed model assembly line balancing problem. At last, use the method of simulation analysis to build the actual simulation model and then find a final optimization solution. Combined with the best allocation scheme in first step, get the final solution of the stochastic U-shaped mixed model assembly line balancing problem.This paper considers the problem between sequencing scheme and stochastic U-shaped mixed model assembly line balancing problem and then tries to design a step-to-step method for this problem. The final results and conclusions can provide theoretical basis for the manufacturing enterprise in the process of scientific developing.