Simulation of the effect of geometrical variation on assembly and holding forces

All assembly situations include joining of parts – by welding, riveting, bolting or using clip fasteners etc. Normally, the force needed to join two parts, i.e. the assembly force, is calculated under nominal conditions. Since all manufactured parts, as well as assembly fixtures, are afflicted with variation, the gap between two flanges that are to be joined may vary. Therefore, also the force needed to close the gap will vary as well as the remaining holding force. For a fixed force produced by a welding gun or an operator, also the remaining force after closing the gap will vary, which may lead to quality problems. In this paper, a simulation method for prediction of required assembly forces as well as holding forces due to initial gap is presented. Three different joining techniques are also discussed with respect to assembly and joining forces