Grouping and sequencing product variants based on setup similarity

Abstract

In some flow shop environments, set-up times between product variants have an important role and are considered more significant than processing times. Therefore, optimal sequence of various product variants is based on improving machine utilisation. A flow shop environment which addresses the set-up criterion where bypassing is not permitted is considered in this paper. A mathematical model is developed and solved using GAMS optimisation software. The non-linear model is then linearised to find exact solutions. A new policy for sequencing product variants is proposed and compared to the exact solutions obtained from GAMS. This sequencing policy capitalises on the commonality between product variants to increase sequencing efficiency. The developed sequencing policy is simple and easy to apply in manufacturing environments. A case study in the label stickers making industry is used for demonstration and validation. Numerical results indicate that the proposed sequencing policy is capable of finding good, and exact solutions in some cases, in less than one second for all studied small, medium and large problem sizes. The solutions obtained using the proposed sequencing policy has a total average of 1.2% relative error which is quite comparable with the solutions obtained using GAMS.

A two-stage ant colony algorithm for hybrid flow shop scheduling with lot sizing and calendar constraints in printed circuit board assembly

“…Raduly-Baka et al (2017) proposed two heuristics based on job grouping to optimize the problem with the idea of constructing the minimum number of component reel modules. Navaei and ElMaraghy (2017) developed a new grouping and sequencing policy for finding the optimal sequence of various product variants to improve machine utilisation. Tóth et al (2018) presented a two-step optimisation method for the machine reconfiguration and workload balancing in the case of multiple PCB batches of different sizes and PCB types.…”