Metal spinning is a near-net-shape forming process used to produce axisymmetric hollow parts, usually with circular cross-sections, that
involves forming sheet metal over a rotating mandrel with the help of
one or more rigid tools called rollers. The selection of rollers,
available in different diameters, profiles, thicknesses and materials,
including plastic, involves blank size, material type, product radii and
desired surface finish.
Metal spinning imparts continuous localized plastic deformation through the feeding motion of the roller(s). Local material deformation
in metal spinning—as opposed to global deformations in deep
drawing—provides inherent advantages, including process flexibility,
non-dedicated tooling, low forming loads, good dimensional accuracy and
surface finish, high material utilization, low production costs, and
improved mechanical properties.
Metal spinning consists of three primary processes: conventional spinning, shear spinning and flow forming, with the primary difference
between the three processes being the wall thickness after spinning.In
conventional spinning, the wall thickness remains nearly constant
throughout the process, with the final wall thickness of the spun part
measuring about the same as the flat blank. A rotating sheet metal blank
takes the shape of a rotating component called a mandrel through the
application of localized pressure by a roller tool. The roller tool
pushes on the blank as it follows a predetermined forming path
consisting of multiple roller passes. The forming action continues
incrementally until the inside of the formed part matches the contour of
the mandrel (Fig. 1). Depending on part size, complexity, material type
and quality requirements, it is sometimes possible to spin some parts
with a single roller pass.
In multipass conventional spinning, the number of roller passes and direction of each pass determines the final wall thickness. When the
roller moves forward, the material thins slightly; when it moves
backward, it displaces metal in the opposite direction to ensure
consistent wall thickness and reduce springback. Improving finish and
accuracy may require intermediate and finishing passes, called
planishing. Planishing passes, designed to remove waviness produced
during the various stages in the spinning process, involve high feed
rates to minimize tangential flow. A final roller pass enhances the
surface finish by reducing the feed and speed while applying a
relatively high radial force.
