An investigation of the job-type performance of priority scheduling in manufacturing cells

In traditional job-shop studies, it is usually assumed that jobs arrive randomly, they have random processing requirements, and measures of performance are taken over all jobs completed within a time period. There are many instances in practice, however, where a group of machines is formed to process a certain set of similar job types. A number of flexible manufacturing systems and group technology cells are examples of such manufacturing environments. In these types of manufacturing environments, the performance by job type is as important as the performance over all jobs. Problems may arise when jobs of a certain type are delayed more than the other job types. Such a situation is more likely to be seen when priorities are assigned based on information that is dependent on the type of a job. This study is an investigation of such variation in the job-type performance of the scheduling rules. It may be looked upon as an exploratory study since there is a lack of published results in this field of scheduling literature. Some fundamental questions regarding the job-type performance of a typical manufacturing cell are answered through a large-scale simulation experiment.