Approximating a global objective by solving repeated sub-problems for an oven scheduling problem
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Accepted version
Date
2024-09-02
Authors
Simonis, Helmut
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Publisher
ModRef 2024
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Abstract
In this paper we describe results for an oven scheduling problem studied during the European ASSISTANT project. This is a multi-stage scheduling problem arising in the production of rotor assemblies for compressors, provided by one of the industrial partners in the consortium. The main resource type is a set of identical ovens, which are used to heat-treat components in different ways. The process for one product may require multiple consecutive steps using these ovens, with specific temperature and process requirements at each step. Multiple tasks of different orders can be processed together in the same oven, if the temperature and process parameters for the tasks are identical. Processing multiple tasks together is more energy efficient, but typically forces some tasks to wait until all scheduled items are available, possibly impacting product quality and creating delays for the orders. The main difference to the oven scheduling problem studied in the literature is that we are not just trying to find an optimal solution to the short-term, detailed scheduling problem, but rather are interested in how selecting different parameters and constraints for the short-term scheduling problem affects the overall long-term, global objective of minimizing energy use, while maintaining the quality of products. Turning ovens off and then on again is considered bad for energy and maintenance reasons, we therefore try to minimize the number of shutdown events over the full planning horizon, while dealing with demand fluctuations over time. Information about jobs to be scheduled is only available within a limited time horizon, we therefore cannot solve the overall problem as one global optimization problem. Results indicate that we obtain a good overall schedule with a simple detailed scheduling model.
Description
Keywords
Scheduling , Global objective , Oven scheduling , Constraint programming , Applied computing , Industry and manufacturing
Citation
Simonis, H. (2024) 'Approximating a Global Objective by Solving Repeated Sub-problems for an Oven Scheduling Problem', ModRef 2024: The 23rd workshop on Constraint Modelling and Reformulation, part of CP 2024: The 30th International Conference on Principles and Practice of Constraint Programming, 2-6 Sept. Girona, Catalonia.