There are two ways to do this: The first method uses the circular circular plate material with the hydraulic force of the tailstock, close to the outer end face of the spherical mandrel and rotates with the main axis. With the help of the hydraulic profiling device, Pressure to make the plate gradually shrink deformation attached to the mandrel to get a hollow hemisphere, and then cut off the excess burrs and welding groove, and then the two hemispheres with argon arc welded into the desired hollow ball blank , And finally made into a valve sphere. The second way is to use flat rough rough board, the difference between the two is spin into a hemispherical shape, but also need to spin out a cylindrical semi-finished product, and then the semi-finished blank in the inner hemispherical core mold, through the pass Tailstock mandrel with the same diameter compacting, and pipe necking the same spinning method, the cylindrical section is gradually shrunk to produce the other hemisphere, and closing the excess metal material attached to the mandrel, and finally cut off excess Part, to get a desired overall hollow ball blank, and finally made into a valve sphere.

The advantages of steel plate spin method: steel source is convenient, the price is not high compared with the steel, to achieve a complete hollow structural sphere. The disadvantage is the need for two core mold, spinning process is complex, the required structure and control of the spinning device are more complex, higher equipment costs, but from the economic efficiency and product quality to resolve, this method is still the best method.