TTHE EFFECT OF LOT SIZE AND PRODUCT STRUCTURE ON MAKESPAN MINIMIZATION IN MULTILEVEL PRODUCT SCHEDULING (Due to 3 Levels of Product Structure with Maximum Parts Are 4 in Each Level)

Production scheduling plays important roles in production system. It directly affects the production capacity whether production capacity will inadequate or excessive which both of them can result lost. Generally, production scheduling is aimed to minimize production and labor cost that is affected by function of time which is total production time or makespan. Minimizing makespan becomes the research objective in this research that is included in the long term research project of The Production System Laboratory of Universitas Atma Jaya Yogyakarta. Some data is used in this research. They are product structures, lot size, setup time, and run time. Product structure used is 3 level of product structure with maximum number of parts are 4 in each level where the combinations of product structure forms are generated to fulfill that consideration. Number of item produced is 30 and lot size evaluated are 5,6,10,15, and 30. Setup time is randomly generated by random number that is varied from 5 to 10 minutes/lot, and run time is varied from 1 to 5 minutes/unit. Gantt chart generation is used to find makespan. Later, hypothesis testing is generated using ANOVA due to the optimum setup time - run time ratio. Based on the whole process, it results that optimum ratio tends to be among lot size 10, 15, and 30. Another result is that the complexity of product structure (in this research is the number of parts) affects the optimum ratio among product structures. Later, it affects optimum lot size that results minimum makespan