Early risk identification and cost-benefit analyses through ergonomics simulation

For cost-beneficial reasons simulations with computer manikins have been increasingly used in the automotive industry for prediction of ergonomics problems before the product and work place exist in physical form. The main purpose of ergonomics simulations is to apply biomechanical models and data to assess the acceptability of the physical work load, e.g. working postures, visibility, clearance etc., which could result in requirements to change the design of the product. The aim is to improve ergonomics conditions in manual assembly and to promote a better product quality through improved assemblability (ease of assembly). Many studies have shown a clear correlation between assembly ergonomics and product quality and that poor assembly ergonomics result in impaired product quality and in decreased productivity. Nevertheless, there are remaining difficulties in achieving acceptance for changes of product and production solutions because of poor assembly ergonomics. A recent study in the Swedish automotive industry showed that huge savings and increased profit margins can be obtained by eliminating ergonomics risk concepts in the very early product development process. The study confirmed a strong relation between poor ergonomics assembly solutions and quality errors of the product (car). There was a substantially increased risk for quality errors and increased costs for corrective measures of the product for assembly items of high and moderate physical work load compared to assembly items of low work load. The quality risk was increased 3 and 3.7 times, respectively. The overall cost for corrective measures in the assembly plant and for factory complete cars was 8.7 and 8.2 times higher for assembly items of high and medium physical work load compared to items of low physical work load. The purpose of this paper is to demonstrate the need for ergonomics simulations of potentially harmful assembly concepts in combination with cost-benefit analyses of conceivable system solutions based on calculation of costs for quality errors related to poor ergonomics and poor assemblability. The intended end result of this research is a model by application of which it is possible to calculate the cost for quality losses and health effects due to poor ergonomics and compare it with the cost for improving the ergonomics with designers, manufacturing engineers and ergonomists as main users