2-Stage Design for a Hybrid Assembly Line with Humans and Robots Considering Automation Difficulty Level: Case Study of the Electrical Equipment Assembly Line

Abstract

Labor force in the manufacturing industry has declined with an aging society, and from a laborsaving perspective, automation using robots is expected for assembly lines. However, there are many tasks on an assembly line; while some such tasks can become easily automated using robots, others are hard to automate due to different automation difficulty levels. Therefore, with the automation difficulty level in mind, a line design is required to configure both human and robot contributions. This study applies a 2-stage design to an actual case in an electrical equipment assembly line and analyzes a hybrid assembly line design with humans and robots that considers automation difficulties from manual work. In the first stage, all tasks are selected as either human or robot tasks, based on the automation difficulty level and the automation rate of the line, using 0-1 integer programming. In the second stage, a line balancing problem is calculated by 0-1 integer programming to minimize the numbers of stations. Subsequently, numerical experiments are solved on the actual electrical product manufacturing line with a commercial solver. As a result, a line design is obtained with a short idle time and a small fluctuation for the time among assembly stations.