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.