Assessing the impact of changing available multiple process plans of a job type on mean tardiness in job shop scheduling

This paper assesses the impact of changing the available multiple process plans of a job type in a production order on mean tardiness using simulation based genetic algorithm approach. A restart scheme as suggested in the literature is embedded into genetic algorithm in order to prevent premature convergence. An algorithm is developed to select a job type that becomes a candidate in order to change the available multiple process plans. Three case studies of varying sizes have been considered to assess the performance of job shop with an objective to minimise mean tardiness. Results indicate that by changing the available multiple process plans of a job type in a production order assists in reducing mean tardiness of a production order. In addition, selecting the best process plan among available multiple process plans on the basis of minimum total production time criterion for a job type does not yield optimal schedule.