Manufacturing: Metal Forming

Sheetmetal Forming - Metal Spinning

The metal spinning process starts with special machinery that produces rotationally symmetrical (i.e. cone-shaped) hollow parts; usually from circular blanks. Shear forming, a related process where parts are formed over a rotating conical mandrel, can be used to produce not only cone-shaped parts but also elliptical or other concave or convex parts. Often, shear forming is used in conjunction with metal spinning. Metal spinning is used as a replacement for the stamping and deep drawing processes.

The metal spinning process starts with a sheet metal blank which rotates on a lathe. The metal disc is pressed against a tool (called a mandrel or a chuck) with a tailstock. The metal disc, tailstock and tool rotate in a circular motion and a roller presses against the metal to form the metal over the tool through a series of passes by the roller. The resulting part is a piece that duplicates the exterior portion of the tool it was formed on. The basic shapes in metal spinning are cones, flanged covers, hemispheres, cylindrical shells, venturis and parabolic nose shapes.

Metal spinning yields pots and pans, vases, lamp shades, musical-instrument parts and trophies. Automotive parts include wheel discs, rims, hubcaps and clutch drums. Other examples include radar reflectors, parabolic dishes, hoppers, concrete-mixer bodies, drums, pressure bottles, tank ends, compensator and centrifuge parts, pulleys, hydraulic cylinders, engine inlet rings and a variety of jet-engine and missile parts.

Some of the advantages of metal spinning include -

1. Low capital-investment
2. Low tooling and energy costs
3. Short setup times
4. Quick and inexpensive adaptation of tooling and methods to accommodate design changes
5. Ability to carry out other operations such as beading, profiling, trimming and turning in the same production cycle with one setup.
6. Forming forces are appreciably lower than competing processes due to localized working.
7. Economical for one-off parts; prototypes; and small, medium and high volumes.
8. Any sheet material that can be cold formed is a candidate for metal spinning including - cold rolled steel, hot rolled steel, aluminum, stainless steel, brass, copper and exotic metals such as titanium, inconel, and hastealloy.
   

Tooling for spinning is relatively inexpensive and simple to employ, translating to a short lead time for parts. Tight tolerancing requirements may require secondary operations, but the advent of automated spinning machines allows more precise forming than with manual spinning machines, with less reliance on operator skill.