A New Ball Set for Tube Spinning of Thin-Walled Tubular Parts With Longitudinal Inner Ribs

Abstract

Tube spinning is one of the old incremental forming manufacturing processes. Recently, tube spinning using balls as forming tools, has been extensively utilized in producing tubular components with longitudinal or helical internal gear teeth, internal grooves or internal ribs. Thin-walled tubular parts with longitudinal inner ribs emerge in order to adapt to the development of aeronautic, aerospace and military industry. Recent development of tube spinning of macro and micro inner grooved tubes and inner geared drums face many challenges. The most important ones are; material built up formation in front of the forming balls, material folding at the tube inner surface, and the forming mandrel failure due to load fluctuations at the root of the forming tooth. These problems have been addressed separately in the literature without a unified approach to simultaneously overcome them. The current study proposes a new ball set design that is claimed to be able to overcome these problems simultaneously. A finite element simulation model for the conventional and the new proposed designs is built and verified. The conventional ball set contains four balls lie in the same plane. The proposed design contains 24 balls distributed in four planes, having 6 balls in each plane. The first plane is set to suppress the built up formation, the second and third plane are set for the main forming process, the fourth plane is set for suppressing the load fluctuation. Each two consecutive planes are shifted by 60 deg from each other to suppress the folding creation. By examining the achieved results, the new design has shown the potential to significantly reduce the built up formation in the front of the forming balls. Also, the reactions at the inner surface of the spun tube have shown significant improvements in both the radial load fluctuation which is responsible of the folding problems and the load in the tangential direction which is responsible of the tooth root failure.