University of Twente Student Theses


The Industrial Bakery Scheduling Problem : solving a complex continuous hybrid flow shop model using meta-heuristics

Bosch, Y.J. (2022) The Industrial Bakery Scheduling Problem : solving a complex continuous hybrid flow shop model using meta-heuristics.

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Abstract:In an automated industrial bakery, the scheduling of different batches of bread is a challenging optimization problem that is NP-hard. We call this the Industrial Bakery Scheduling Problem (IBSP). A large body of research exists for industrial process optimization. However, existing optimization methods leave out critical factors in the production process, such as waiting times, change-over times and differences in processing time or machine settings between various recipes. This leads to solutions that are insufficiently accurate. The IBSP problem can be described as a hybrid flowshop problem with multiple stages that has anticipatory, sequence-dependent batch setup times, no waiting in between batches and with a total makespan-minimization goal. Importantly, batches flow on the line continuously, with potentially hours between the first and last bun in a batch. In this thesis we build a novel flow-shop model that meets those requirements, and that can calculate the makespan of hundreds of production plans per second. Additionally, we integrate several machine variants into this model, to simulate the effects of added change-over flexibility on total makespan. We integrate and test several well-known construction- and meta-optimization heuristics and validate the model on a test-case. Finally, we experiment with the efficacy of optimization methods and machine variants for a set of randomly generated production plans with up to 20 recipes, with satisfactory results. Our model structure allows for fast and efficient optimization of realistic problems that were previously out of reach for engineering staff at the host company, representing a significant improvement to their body of knowledge, and potentially hundreds of work-hours saved per customer.
Item Type:Essay (Master)
Royal Kaak
Faculty:BMS: Behavioural, Management and Social Sciences
Programme:Industrial Engineering and Management MSc (60029)
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