JOB SHOP SCHEDULING IN PULL TYPE PRODUCTION ENVIRONMENTS

The tremendous increase in the competitive advantage that the Japanese manufacturing companies have experienced in the past decades over their American counterparts has been widely attributed to their use of just in time with Kanban among other things. Slow down in the increase of productivity and loss of business to foreign competitors have made the American manufacturing managers increasingly aware of the inadequacy of the classical push type production systems. In the last decade the American manufacturing managers have shown an increasing amount of interest in abandoning these push type systems and adopting the more current pull type systems such as just in time with Kanban . The difference between pull and push systems lies in the control structure. In the classical push system, a work center has no control on the arrival of the jobs to be processed. Once the processing of a job is completed, it immediately gets pushed to the next work center. Hence the inventories at a given work center in a push system consist of nonprocessed jobs. In a pull system, on the other hand, a work center has no control on the delivery dates (the date a job needs to be delivered) but can specify the time a job has to arrive to be processed. Hence in a pull system the inventories on a given work center consist of processed jobs, waiting to be pulled by the next work center. Most research in the scheduling literature so far has focused on push type manufacturing systems. In this thesis we study and analyze two major scheduling problems which are relevant for pull type systems. The first problem considers the scheduling of jobs on a single machine without lot sizing. The second problem is similar to the first one except that both scheduling and lot sizing are done simultaneously. We focus on The Single Machine Scheduling Problem. Extending the results to The Multiple Machine Scheduling Problem requires further research. Some ideas along this line are proposed