Hand/Arm Forces with Pneumatic Nail Gun Actuation Systems

Abstract

A biomechanical model is presented to estimate cumulative user hand/arm force associated with two pneumatic nail gun trigger systems. The contact actuation trigger (CAT) can fire a nail when the user holds the trigger depressed first and then “bumps” the nail gun safety tip against the workpiece. With a full sequential actuation trigger (SAT) the user must press the tip against the workpiece prior to activating the trigger. The SAT is demonstrably safer in reducing traumatic injury risk, but increases the duration (and magnitude) of tip force exertion. Time integrated hand force was calculated for a single user from measurements of the tip contact force with the workpiece and transfer time between nails as inputs to a quasi-dynamic model of nailing in two task orientations. Application of the model shows the hand/arm force dependence upon the orientation of the workpiece in addition to the trigger system. Based on standard time allowances from work measurement systems (i.e. MTM - 1) the model results suggest that efficient application of tip contact force with the SAT would reduce total hand/arm force exertion attributable to this trigger system for this user. The present model is useful for considering differences in cumulative hand/arm force exposure between the SAT and CAT systems and the user perceptions and practices that result from these differences.