Multi-Objectives Finite Capacity Scheduling of Make-and-Pack Production With Options to Adjust Processing Time

Abstract

Make-and-pack production is characterized by two stages of production namely, "make-stage" and "packstage" where each stage consists of parallel processing units. In make-stage, raw materials are converted into final products by batch processing. Then, the final products are packed into containers in pack-stage. This paper develops finite capacity scheduling (FCS) system of make-and-pack production with multi-objectives and options to adjust processing time (OAPT). Multi-objectives including minimizations of total tardiness, total earliness, total flow time, and total processing costs are conflicting and a compromised solution is needed. Moreover, the processing time can be adjusted by adding some special chemicals. This paper proposes mixed-integer linear programming models to determine the compromised solution by using weighted average of satisfaction levels (WASL) of all objectives as performance measure. The proposed compromised solution method consists of three steps, (1) determining the best and worst values of each objective, (2) determining the initial compromised solution of all objectives when OAPT is not included in the model, and (3) determining the compromised solution with OAPT. The effect of chemical costs to the OAPT is evaluated. The results showed that the proposed FCS system offered a compromised solution between conflicting objectives. The compromised solution is relatively good but not the best for all objectives. The OAPT can improve the performance of the system and it is significantly affected by the chemical cost per unit. When the chemical cost per unit is reduced, the special chemical is used more to reduce processing time per batch and then the performance measure is more improved.