________________________________________ † : Corresponding Author The Application of Genetic Algorithm on U-Shaped Line Balancing with Stochastic Processing Times Hotna Marina Sitorus† and Cynthia P. Juwono Industrial Engineering Department Parahyangan Catholic University, Bandung 40141, INDONESIA +62-22-2032 700, Email: {nina, juwonocp}@home.unpar.ac.id Deci Marlina Industrial Engineering Department Parahyangan Catholic University, Bandung 40141, INDONESIA Abstract. The purpose of this paper is to describe the application of Genetic Algorithm (GA) to solve a type II U-shaped line balancing problem. Type II line balancing aims to obtain the minimum cycle time in which an assembly can be produced using number of workers available. To accommodate the differences between operators, this paper uses stochastic processing times. To evaluate the performance of the proposed GA, various cases are developed. The cases have different characteristics, such as the complexity of precedence structure, the number of workstations available, and the standard deviation of processing times. This paper also studies the impact of crossover and mutation rates used in Genetic Algorithm on the performance of the proposed GA. Experimental results show that Genetic Algorithm can be used to minimize cycle time in U-shaped line balancing. The sensitivity analysis shows that the values of GA parameters influence the quality of solutions. In low mutation rate, the bigger crossover rate is, the smaller the cycle time obtained. Moreover, regardless of the crossover rate, the higher the mutation rate, the higher is the probability to obtain better solution. It is also found that a high standard deviation of processing time results in a long cycle time and the complexity of precedence structure affects the result obtained. Keywords: U-shaped line balancing, Type II line balancing, Genetic Algorithm. 1. INTRODUCTION In contrast to a traditional straight line, in a U- shaped line workstations are arranged so that both ends of the line are closely together forming a "U" shape. Many shop floors arrange their production lines into U-shaped lines as a consequence of application of Just in Time concept. U-shaped lines offer many advantages compared to traditional straight lines, including the improvement of operator visibility and communications, the increase of operator skills to perform most of the operations in the line, the flexibility of output rate adjustment, and the requirement of the number of stations that is never more than the traditional lines (Miltenburg and Wijngaard, 1994). Miltenburg (2001) studied 114 US and Japanese U- shaped lines and found that when the U-shaped lines were implemented to replace existing traditional production lines, the productivity improved by an average of 76%, WIP dropped by 86%, lead time shrunk by 75% and defective rates dropped by 83%. With respect to line balancing, the task assignment in U-shaped line balancing is not only done by moving forward along the precedence diagram, but also backward, or combination of both directions. As a result, the first workstation in a U-line may contain the first operation and the last operation. Figure 1 illustrates an example of a U-shaped line. Miltenburg and Wijngaard (1994) introduced optimization and heuristic models to solve U-shaped line balancing problems. Ajenblit and Wainwright (1998) used