Development of scheduling system considering statistical distributions of processing times for human operators

A new scheduling method is proposed, in this paper, to consider the statistical distributions of the processing times which are represented by normal distributions for the manufacturing systems where the human operators carry out the machining operations by using manual machine tools. The proposed scheduling method consists of two steps. In the first step, the machining schedules are determined for the individual machine tools based on average processing times by using utility value based method. In the second step, the candidate human operators are assigned to the individual machine tools taking into consideration of the statistical distributions of the processing times. A new scheduling system is also developed to generate suitable schedules based on the proposed scheduling method by using the processing time data executed by the combination of human operators, manual machine tools and machining operations. Some case studies have been carried out to verify the effectiveness of the proposed method.