A Full Kinematic Model of Thread-Starting for Assembly Automation Analysis

This work addresses the geometry of threaded fastener insertion at a detailed level in order to determine the nature of contact between a bolt and nut during the initial phases of thread mating. The assembly problem was modeled as a constrained three-dimensional analysis to gain an understanding about how contacts between the bolt and nut change during the thread starting counterclockwise motion. We introduce a fully detailed thread profile model which is parametrically adaptable to all practical thread forms. From this geometric representation, we derive contact state maps graphically represented as axial discs. From these maps we show the phase relationship of the bolt and nut in the critical thread-starting process. This model is based on the premise that an unspecified active or passive device will be employed for correcting alignment errors. The model serves to visualize the contact conditions which could lead to wedging and jamming events, and provides one component for such analyses.