Lot-splitting and scheduling algorithm of multi-level assembly job shops

Is practical extension of job shop, it is oriented to the manufacturing of assembly products with multi-level BOM structure. The products need to go through two stages of parts processing and assembly. The assembly of higher parts can only begin after the complete set of its direct parts, that is, there is a hierarchical coupling constraint between the parts at all levels. Aiming at the difficult coordination of differentiated parts' processing and assembly progress in multi-level assembly job shop, the reasonable batching of parts could improve workshop mobility, achieve more flexible progress coordination and shorten the production cycle. A batch scheduling model for minimizing makespan in such workshops was presented. The batch division strategy in the processing/assembly phase and an improved genetic algorithm based on feasible region search were proposed. The initial population generation, crossover and mutation of this improved genetic algorithm considered the dynamic constraints brought by the batch change, which could always guarantee the legitimacy of chromosomes in the evolutionary process. The basic performance of the proposed algorithm was verified by experiments, the adaptability of different batching strategies to three typical product structures was revealed, and the good effect of collaborative complexity oriented strategy was illustrated. © 2021, Editorial Department of CIMS. All right reserved.