Batch Scheduling for a Single Machine with Forgetting Effect to Minimize Total Actual Flow Time

Abstract

Abstract. This research discussed a batch scheduling model for a single machine with increasing processing time due to forgetting effect as the operator of the machine must relearn the operation after a setup time conducted between two consecutive batches. The forgetting effect leads to a condition where processing time of parts in a batch scheduled at a position will be longer than that of parts in the next scheduled batch in the backward scheduling approach. The objective function is minimizing the total actual flow time defined as total interval times between arrival times of all parts in all respective batches and their common due date. Decision variables are the number of batches, batch sizes and the sequence of the resulting batches. This problem is solved using the Lagrange Relaxation method. The result of research shows that total actual flow time can be minimized by sequencing batches according to the LPT rule in the backward scheduling approach. Keywords: forgetting effect, batch scheduling, the total actual flow time