Development of scheduling system considering statistical distribution of machining time executed by human operators

In the scheduling problems of the manufacturing systems with human operators, it is not easy to consider variation of machining time which are different from operator to operator. New scheduling method is proposed, in this paper, to consider the statistical distribution of machining time executed by human operators. It is assumed that the machining time executed by human operators are obtained by normal distribution. The proposed scheduling method consists of two steps. In the first step, the sequences of machining operations are determined for the individual machining tools by using utility value based method. In the second step, the candidate human operators are allocated to the individual machining tools taking into consideration of the statistical distribution of the machining time of the individual human operators. The scheduling system is also developed to carry out the proposed scheduling method by using machining time database. Some case studies have been carried out to verify the effectiveness of the proposed method.