Metal Spinning / Flow Turning

Metal Spinning / Flow Turning

Spinning is a process used to produce an axis-symmetric hollow shape by the application of lateral pressure from a forming tool, to a rapidly revolving circular blank of sheet material, causing it to assume the shape of a former that is rotating with it.

The principles of flow turning
Thicker sheet is plastically deformed by a pressure roller over a former. Metal is thinned.

Series of metal spinning operations
Deformation in metal spinning is a mixture of bending and stretching.

  1. Metal spinning involves spinning a flat circular blank of the sheet material on to a special lathe to which a former is attached. This former provides the inside shape and dimensions of the article being produced. Hardwood formers are used. With a lever-like tool the blank is progressively fashioned over the former until it fits like a skin.
  2. Simple forms like a dish-shaped parabola, for example, can be made in one operation. Two or more formers can be used for more complex shapes.
  3. A high level of manual skill is involved. Automatic spinning machines with robot assistance are also used to produce higher volume production, e.g. hot-water cylinder bases, with a cycle time of 25 s per component.
  4. Can be used as a manual batch or prototype process, with low tooling costs.
  5. Adequate lubrication is required, such as beeswax, tallow or soap.
  6. The thicker, the harder and the larger the diameter of the blank, the slower the spinning speed will be, e.g. thin copper foil (25 mm in diameter) 2500 rev min – 1. 5 mm thick brass (2m in diameter) 250 rev min-1.
  7. In the “flow-turning” process, thick gauge material is made to flow plastically by pressure rolling it in the same direction as the roller is travelling, so that a component is produced in which the wall thickness is much less than that of the original blank. This is a more automated process than metal spinning.

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