Grey Parallel Assembly Line Balancing

Purpose: The purpose of this paper is to solve a grey parallel assembly line balancing problem with type-I (G-PALBP-I) to minimize the number of stations under the major constraints and restrictions of the PALs. Design/methodology/approach: A manufacturing system with parallel assembly lines (PALs) consists of at least two assembly lines placed next to each other in the facility layout. To design real-life PAL applications, the processing durations of the tasks may not always be fixed due to workers getting tired or making mistakes. In addition, the variability in customer demands may also affect the cycle duration called the total processing duration of a station. To better reflect the real-life applications of PALs, task and cycle times are expressed with grey system theory and grey numbers. A binary integer linear programming model is proposed to solve the G-PALBP-I. Findings: The proposed model is implemented to the PAL systems designed by using a simple assembly line data in the literature. The results show that considering precedence relationships and variability in task and cycle durations provides a more flexible and consistent perspective. Originality/value: The grey system theory and grey numbers, to the best of the authors’ knowledge, have not been considered to describe the uncertainty of task and cycle times in PALBPs. Therefore, this study provides important insight to both researchers and decision-makers in practice.