What is Sheet Metal Spinning?
Sheet Metal Spinning (also known as metal spinning or spin forming) is a metal forming process in which a sheet metal is formed into a cylindrical part by rotating it and applying forces on it.
In sheet metal spinning, there is no removal of the material, but it involves only the shaping of the sheet metal by application of forces.
Examples of metal spinning includes;
- Satellite dishes
- Rocket nose cones
- Metal vase
- Musical instruments, etc.
How Sheet Metal Spinning is done?
In sheet metal spinning operation, the sheet metal piece is rotated at a high speed and the rollers are pressed against the rolling sheet.
The sheet metal is supported by mandrel so when the rollers presses the sheet, it takes the shape of the mandrel and thus desired shape is obtained.
The parts prepared by sheet metal spinning have rotational symmetry and most of the parts are hollow shaped (like cylinder, hemisphere or cone).
Sheet metal spin forming is generally performed on a manual lathe machine or a CNC lathe machine.
During the metal spinning operation, the main essential components are blank, mandrel, roller and a spinning machine tool (i.e manual or CNC lathe).
The blank used for spinning operation is a disc shaped sheet metal piece which is cut out from the stock of the sheet.
The mandrel is a solid device which helps the sheet blank to take the desired shape when pressed with a roller. And this mandrel is attached with the rotating chuck of the lathe.
Well, there are also various types of mandrels for different purposes, but in sheet metal spinning (specially for spinning of complex parts) multi piece mandrels are used.
The mandrel does not experience much wear during the spinning operation, so sometimes wooden mandrel or plastic mandrel are also used.
But for large scale production purposes, the metal mandrel is preferred.
The sheet metal blank and the mandrel are clamped between the headstock and tailstock of the lathe and then it is rotated at a high speed.
During the rotation of these parts, the force is applied with the help of a roller tool which presses the sheet metal and causes it to bend and take the shape of the mandrel.
For complicated shapes or for the sheets having more thickness, the roller tool is passed multiple times over the sheet to achieve the final shape.
The rollers used for pressing a sheet metal are generally made up of steel or brass and they are attached to a lever.
The spinning rollers are cheap and they experience very little wear during the spin forming operation.
Different spinning methods used in spin forming
In spin forming, there are two different methods used for spinning.
- Conventional spinning
- Shear spinning
In convention spinning, the roller pushes the blank against the mandrel and this forms the shape of the mandrel.
The final resulting part will possess the shape of the mandrel and it will have a diameter smaller than the blank diameter.
Also the thickness of the spinned component will be constant throughout.
In shear spinning, the roller bends the sheet blank over the mandrel plus it also applies a downward force when it proceeds.
As the stretching of the sheet blank occurs, it will reduce the thickness of the spinned component.
Also in shear spinning, the outer diameter of the spinned part remains equal to the original blank diameter.