Modified analytical method to calculate the assembly and separation forces of cantilever hook-type snap-fit

In this study, a new analytical method to calculate the assembly force and separation force of cantilever hook type snap-fit was proposed. Finite element analysis and experimental measurement were performed to verify the new approach. It was found out that the conventional analytical method had a few limitations. The solution was only applicable when the retention face angle was small, and there existed a critical value of retention face angle where separation force unreasonably decreased with increase in deflection. The new approach considered large deflection of retention feature and resultant moment term in addition to the previous method, and the solution was obtained explicitly. The new analytical solution could be applied to large face angles without any divergence, and showed good agreement with finite element analysis results. When the face angle was relatively small, both conventional method and new method showed reasonable results; however, when the angle was large, only the new analytical method showed reasonable results. Experimental investigations of forces during assembly and separation showed that the measured forces were much smaller than the predicted values by analytical methods and finite element analysis. The forces were strongly dependent on the rigidity of the mating part and the magnitude of radius at the edges of beam and mating parts. It was found from experiment that the separation force nonlinearly increased as clearance decreased.