Evaluating the effects of activation mode, torque and horizontal operatingdistance on hand-arm response while operating pneumatic screwdrivers

The objective of this study is to evaluate the influences of activation mod e, torque and horizontal operating distance on hand-arm response while oper ating in-line pneumatic screwdrivers, Hand-arm response was investigated in terms of finger force exertion, flexor digitorum electromyography, and han d-transmitted vibration. Two activation modes (push-to-start, and trigger-t o-start), two torque levels (low, and high) and three horizontal operating distance (far, middle, and near) were evaluated, Thirteen healthy mate subj ects drove screws into an iron plate with pre-tapped screw holes using in-l ine pneumatic screwdrivers in randomly ordered experimental conditions. The results indicate that the use of push-to-start mode, not only required a g reater holding force involving forearm muscular exertion and middle, ring a nd small finger forces, but also incurred a greater hand-transmitted vibrat ion than the use of trigger-to-start mode. Higher torque caused a greater h and-transmitted vibration and required a firmer grip than lower torque. A m iddle distance level (18-30 cm away from the table edge) is recommended as it is found to have the least hand-transmitted vibration and requires less finger force exertion. Relevance to industry The findings on the evaluation of the influence of activation mode, torque, and horizontal operating distance on hand-arm response can provide useful information for the design of assembly tasks using pneumatic screwdrivers a s well as the design of powered hand tools. (C) 2001 Elsevier Science BN. A ll rights reserved.