Decomposition based extended project scheduling for make-to-order production

Abstract

Project scheduling has a critical function for many companies. Although there is a vast literature dedicated to the development of solution methodologies, the real-life applications of those techniques are few and often require over-simplification of the real-life problem. This study deals with the implementation of a project scheduling routine for a “make-to-order” machinery manufacturer. Although the problem is very similar to a resource-constrained project scheduling problem (RCPSP), which is a well-known and well-studied problem in the literature, it has multi-project and multi-mode components which make the project planning more challenging. Because of the multi-dimensional complexity of the problem, it is called a “Rich Project Scheduling Problem”. Our approach employs two techniques to deal with the issue of complexity. The first one is regarding calculation of the latest start time for each activity in the project. The second one is the decomposition method that includes breaking down the big problem into small manageable pieces. The approach was tested on real-life problems of a machine-building company. We also built more complex test cases from the real projects for testing purposes. Our approach produced high-quality solutions to the complex project scheduling problems within reasonable time limits. This work contributes to current research in several ways. An extension to the RCPSP formulation to include multi-project and multi-mode problems is introduced and successfully used for solving real-life problems. Additionally, activities of an RCPSP can be split into multiple sub-activities. Doing so is called preemption. The proposed formulation permits mode-switching during the execution of an activity, and it uses an alternative methodology to calculate latest activity start times.