Optimization of Injection Molding Shop Scheduling Based on the Two-Stage Genetic Algorithm
Injection molding shop Scheduling is a large-scale parallel machine scheduling with process constraints, time constraints, earliness/tardiness penalties and due window constraints. Given the complexity of injection molding shop scheduling, a two-stage gen
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Optimization of Injection Molding Shop Scheduling Based on the Two-Stage Genetic Algorithm Jin-ping Zhou and Hu Fu
Abstract Injection molding shop Scheduling is a large-scale parallel machine scheduling with process constraints, time constraints, earliness/tardiness penalties and due window constraints. Given the complexity of injection molding shop scheduling, a two-stage genetic algorithm is presented: the first stage is to partition jobs to machines, and the second stage is to sequence jobs for each machine. A simulation model for solving injection molding shop scheduling problem is proposed. For determining the optimal starting time of a single machine, a rulebased heuristic algorithm is also proposed. The application demonstrates the reliability and validity of the algorithm and simulation model. Keywords Due window • Earliness/tardiness penalties • Injection molding • Parallel machine scheduling • Procedure constraint
6.1 Introduction The general processes of the plastic injection company which makes to order are: injection, painting, printing, assembly. According to the differences of orders and product requirements, we can choose one of the general processes or all. But the injection process must be the first one. The different processing abilities of machines between the injection and follow-up crafts necessities the temporary storage for products after plastic injection. For direct molding products, the time of temporary storage determines the inventory cost and other related costs. The indirect molding products which have some rest processes need temporary packaging (dust requirements) and storage, transportation. If the injection process is delayed,
J. Zhou () • H. Fu School of Mechatronics Engineering, Guangdong University of Technology, Guangzhou, China e-mail: [email protected] E. Qi et al. (eds.), The 19th International Conference on Industrial Engineering and Engineering Management, DOI 10.1007/978-3-642-37270-4 6, © Springer-Verlag Berlin Heidelberg 2013
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the follow-up processing plan is often disrupted, and even causes the tardiness. Therefore the scheduling of injection molding shop is the most important aspects of reducing the overall production costs. Injection molding shop scheduling (IMSS) has two critical parameters in consideration: the injection pressure and the product’s color. The injection pressure determines the type of injection molding machine (process constraints), the product’s color determines the setup time (processing time constraints). The aim of IMSS is how to partition the existing jobs (orders) to the injection molding machine reasonably and find out the best process sequence of these jobs to ensure follow-up process work normally and minimize the earliness/tardiness (E/T) penalties.
6.2 Problem Description IMSS can be stated as follows: 1. There are n independent jobs (defined by set J) working on m independent machines (defined by set M); 2. Due to the injection pressure, Ji (I D 1, 2, : : : , n) are only allowed to work on some machines
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