Ergonomic design and evaluation of gemstone polishing workstation

Objectives. Gemstone polishers suffer from musculoskeletal problems due to constrained working postures, substantially influenced by the poor design of conventional gemstone polishing workstations. The present study investigated the effects of three workstation adjustment parameters (illumination at workstation, polishing height, tool post position) on postural angle, muscle activity and perceived postural discomfort in order to develop recommendations for new gemstone polishing workstations. Methods. Twelve professional gemstone polishers performed the polishing task on a prototype test-rig in 27 different test conditions. Taguchi's L₂₇ orthogonal array was employed to estimate the optimum setting for gemstone polishing workstation design. Results. Study variables had a significant influence on postural angles. Polishing height substantially influenced muscle activity and perceived discomfort in the shoulder and lower back region. Tool post position was found to be the determinant factor for forearm muscle activity and perceived discomfort in the wrist/forearm region. Based on the findings, illumination of 1500 lux, polishing at 15 cm above the elbow height and a 20° tool position was recommended. Conclusions. Our findings present an alternative approach to using Taguchi's design of experiment for workstation improvement, which has received very little attention in ergonomics studies. A confirmation test was conducted to validate the study recommendations.