A bi-criteria heuristic for solving the assembly line balancing problem

The article presents the results of research concerning a manual assembly line. The discussed bi-criteria heuristic aims to take into account both the minimization of idle times and the workload of employees involved in the assembly process. As is well known, not every operation requires the same effort or the same physical movements. The presented method formally incorporates (using RULA and REBA methods) the contribution based on the workload of each line employee, and the obtained results are used to correct the line balance previously derived based on known heuristic methods for which the optimization criterion is solely machine downtime or employee idleness at the assembly station.

1. INTRODUCTION

The first assembly line for the Ford T was designed in 1913, thereby revolutionizing the mass production process. The introduction of this type of production allows for a significant acceleration of production while simultaneously reducing its costs. Today, production systems based on flow production lines are ubiquitous and apply to most products. The phenomenon of assembly line balancing was first described [10] in the 1950s. The basis of the balancing problem is the assignment of a set of tasks to an ordered set of workstations so that precedence relations are satisfied and quality indicators are optimized. An assembly line is considered balanced when all operations have been performed without violating any of the assumptions regarding assembly line production (indivisibility of operations, adherence to precedence relations). Although the balancing problem has been known for years, new algorithms and modifications to already known algorithms are still being proposed. Workers on manual assembly lines are exposed to injuries due to [1]:

− manual performance of tasks while maintaining a constant posture during work, − forced body position at work (unnatural positions of the whole body and\/or body segments, e.g. (…)