A Lot Sizing and Scheduling Approach on Non-Identical Parallel Machines for Cement Grinding Process Considering Process-Specific Characteristics

Integrating the lot sizing and scheduling problems for improving capacity utilization in process industries is crucial. In order to deal with this problem realistically and to obtain applicable schedules, it is a prerequisite to consider the typical characteristics of the industry under consideration. From this point of view, in this study, the lot sizing and scheduling problem in cement grinding, a multi-product, multi-period optimization problem with non-identical parallel machines, is addressed by considering the unique and industry-specific characteristics of the process. Besides applicability, it is aimed to create schedules that minimize total costs, including inventory holding, production, electricity, and lost sales. A lot sizing and scheduling model (LSM) based on the General Lot Sizing Problem (GLSP) and a capacity control model (CCM) derived from LSM has been developed for the considered problem with these objectives. The proposed approach based on the cyclical running of LSM and CCM has been applied for one year using the real data of a firm operating in the cement industry. The performance of this approach has been evaluated by comparing it with the firm's realized performance during that year. As a result, the proposed approach has significantly reduced inventory holding costs by 47.51%, production during setups by 62.54%, production after setups by 1.49%, and electrical energy by 8.65%.