Single-stage setting of blind rivet nuts without pre-drilling

<jats:title>Abstract</jats:title> <jats:p>The increasing use of thin-walled profiles in automotive battery housing construction is leading to a growing demand for one-sided access mechanical fasteners. Currently, the installation of blind rivet nuts still requires pre-drilling using chip-forming operations. In Meschut and Meyer (Vorlochfreies Setzen von Funktionselementen mittels Fließformen, Europäische Forschungsgesellschaft für Blechverarbeitung e.V. (EFB), Hannover, 2021), a chipless, two-step method for installing blind rivet nuts was developed, in which flow-drilling is the initial step. To eliminate the pre-drilling operation and optimise the joining process of blind rivet nuts, a pilot-hole-free joining method using a flow-drilling process is being pursued. The use of these blind rivet nuts can significantly simplify the joining process by eliminating chip-forming pre-drilling operations. Additionally, the screw-through capability reduces screw variance in automated fastening, optimising the feeding process by minimising the risk of incorrect screw selection. This work aims to develop a single-step process for the installation of a blind rivet nut. To achieve this, it is necessary to design the geometries of both the blind rivet nut and the flow-drill former, which also serves as the mandrel for the blind rivet nut. In addition to the geometries of the tools and functional elements, the flow-drilling process itself has been developed. Special attention is given to the pull-through and the formation of the closing head. To optimise the closing head formation, an iterative optimization process was used. The quality of the pull-through is improved by varying the tip geometries and adjusting the process parameters during flow-drilling.</jats:p>