Job release and labour flexibility in a dual resource constrained job shop

Most of the past research in the area of job shop scheduling have used a model that simply equated job arrival with the release of the job to the shop floor for processing. Another common characteristic of this research is that it has ignored the worker altogether or confined the worker to a single type of machine. This study examines the role of labour flexibility in conjunction with the shop’s ability to regulate the type and number of jobs active on the shop floor for processing. The release mechanisms that regulate the jobs on the shop floor consider both job and shop information in determining when a job should be released for processing. Labour flexibility, such as might be achieved through worker cross-training, enables workers to operate more than one type of machine without any loss in productivity. Two release mechanisms with three levels of labour flexiblity and two labour assignment rules are simulated in this study using two levels of job due date tightness. The shop performance is measured using several of the traditional measures as well as incremental and total cost. Results presented using statistical and graphical analysis show that there is no statistically significant differences in the performance using finite loading and infinite loading release mechanisms. Also, the inclusion of the minimum increment of labour flexiblity produces the maximum performance improvement. Succeeding increases in labour flexibility show a diminishing return in shop performance.