A Study on Sophisticated Production Management for Engineer-to-Order Production: A Mixed Integer Programming Formulation for Production Scheduling

Engineer-to-order (ETO) production in which products are designed and manufactured in response to customer orders is required to respond flexibly to customer requests at various stages from design to maintenance. This characteristic makes it difficult to apply a standard production planning strategy which divides the planning into three phases, i.e., long-term, medium-term and short-term planning (production scheduling), because there are large discrepancies among the phases and rescheduling requires a lot of man-hours. We proposed a production planning framework that unifies the granularity of resources and unit time in all of the planning phases aiming to reduce the discrepancies, and a model that is commonly used in the three phases of planning was organized as flexible job-shops. This paper provides a mixed integer programming formulation of the production scheduling problem based on the model considering the following characteristics of the target ETO production site: (1) The planner has discretion in shortening required processing time; (2) Operation time is limited to day time of weekdays; (3) Overtime works can be accepted if necessary; (4) Some operations of multiple parts must be processed at the same time on the same machine. A numerical experiment showed validity of the model.