TORQUE VIBRATIONS IN AUTOMATIZED SCREW ASSEMBLY - REASONS, ELIMINATION AND VIRTUAL TESTING

摘要

Today the torque controlled tightening method for screw assembly is an established process in industries undertaking large scale productions. In this tightening method an instability of friction during the tightening procedure leads to an imprecise stop of the electronic tightening tool affecting the preload. Besides this heavy noise emission occurs due to vibrations. Because of shorter and shorter cycle times in automated screw assembly, higher precision requirements, new surface pairings (e.g. Cr(Ⅵ)-free) with changed coefficients of friction and more complex assemblies with difficult access to the joint, result in an increased number of torque vibrations on automatized screw assembly (also called stick-slip). Due to highly interconnected production flows, the productivity is hereby significantly interrupted. This means significant financial loss because of a small screw which stops the entire production line. This contribution entitles the reasons for the origin of torque vibrations as well as advices for elimination.