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.
- 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.
- 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.
- 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.
- Can be used as a manual batch or prototype process, with low tooling costs.
- Adequate lubrication is required, such as beeswax, tallow or soap.
- 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.
- 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.
Read more: Metal Spinning / Flow Turning