Ergonomic Evaluation of Power Tool Use at Different Task and Tool Related Conditions Using a Mechanical Test Rig, Electromyography and Subjective Evaluations

Abstract: Workers within production and assembly lines are often exposed to ergonomically unfavorable tasksand conditions. Reaction forces and reaction torques generated by industrial power tools may causenot only discomfort but also health issues and injury. The forceful tasks in combination with highlyrepetitive hand-arm motions and prolonged tool use paves the way for loss in workforce capacitywhich in turn can lead to great losses in productivity and product quality. An umbrella term for themany injuries and diseases that may arise from the use of such tools is Cumulative Trauma Disorders(CTD).This study aimed to investigate the ergonomic effect of power tool use for various tool and taskrelated conditions. The study required the setup of a test rig with a simulated handle of the tool. Theergonomic impact was assessed by measuring the torques associated with different tighteningstrategies, as well as measuring the angular displacement of the tool handle. By varying the jointstiffness and workplace orientation, the complexity of the task was varied and thus quantified.Measurements of muscle activity during each tightening procedure provided a quantification of thephysiological impact on the operator. By combining the measurements on the operator withsubjective assessment of perceived exertion and discomfort, a more holistic perspective on thetightening procedure was obtained.The results obtained from the study stressed the negative impact on the operator which the QuickStep tightening strategy on medium hard joints implies, regardless of workspace orientation. TheTurbo Tight and Tensor Pulse tightening strategies turned out to generate the lowest reactiontorques and handle deflections, regardless of joint stiffness and workspace orientation. The findingsfrom the muscle activity measurements in combination with the subjective evaluation methodsfurther confirmed the mildness of the Turbo Tight and Tensor Pulse strategies. Moreover, horizontalworkspace resulted in lower tool handle deflection compared to vertical workspace for all tighteningstrategies and joint stiffnesses.