Features of metal spinning techniques used by metal spinners and flow forming specialists
The traditional term “metal spinning” typifies a group of forming processes applied to metals for the production of rotationally symmetrical hollow shapes. Common to all of these is the rotation of the spun metal and tools which produce the variety of shapes.
The general classification of these metal spinning processes, which is also covered by DIN standard 8582, is based on the internal stresses placed upon the material by metal spinners. In the metal spinning process, these stresses occur as either a combination of tension/compression or just compression. The type of stress generated is dictated by the technique applied to the spun metal in order to arrive at the correct shape for the spun metal part.
Accordingly, DIN standards 8584 and 8583 differentiate between “metal spinning” where the material is plasticised by compression and tension, and “metal flow forming” where deformation results from compressive force alone. Under metal flow forming, the standard further differentiates between metal shear forming (or metal flow turning) and metal cylindrical flow forming.
Cylindrical metal flow forming is often abbreviated to “metal flow forming”. The term shear metal forming refers to conical or radiused metal forms. Additionally, metal surface enhancement techniques such as planishing and smoothing are applied by metal spinners. Planishing and smoothing can be generically referred to as “metal flow forming”.
In the case of spun metal, the starting 'metal spinners blank' is a sheet metal disc. Usually there is no change in metal thickness during the forming process. Variations in metal wall thickness can only be introduced by using appropriate working parameters. Virtually any metal spun shape can be produced within limits dictated to by material failure.
In the case of metal flow forming, the starting 'metal spinners blank' is a tube or cup shape with parallel sides, which has a taper or radius, this being formed to a finished spun metal part by reducing the wall thickness by a pre-set value. The difference between metal flow forming and metal spinning is the intentional reduction in wall thickness employed in metal flow forming.
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