A New Approach for Assemblability Assessment Using Time and Postural Analysis - a Case Study

This paper explores a new approach to assess assemblability of manual assembly. Assessment of assembly is a prerequisite to optimize an assembly process. Traditionally assemblability is assessed by Design for Assembly (DFA) tools and Time motion studies. However, DFA tools do not usually take into account the in uence of human postures whereas time motion studies focus typically on bench work type of jobs. In order to assess the dif culty of a manual assembly process, we must take into account both the static aspects of the job (represented by dif culty of maintaining a posture) as well as its dynamic aspects (difficulties associated with moving from one posture to another). So, we propose a method that combines both time and postural analysis for the assessment of assemblability. The tool used for the static analysis is called Rapid Upper Limb Assessment (RULA); for dynamic analysis we propose a method of time analysis that is based on a ratio of time spent in ne and gross motions carried out in an assembly process. The dif culty of assembly of a series of manual assembly tasks carried out in laboratory was assessed by this method and correlating the assessment with the feedback obtained from the subjects who carried out these assembly tasks. A video recording of the assembly tasks of a desktop personal computer frame assembly was used as the case study. The results show that there exists a signi cant correlation between the subject feed backs and the combined dif culty scores