There are thin wall balls and hollow balls cast abroad, and there are also castings cast at home, but the quality of castings can not pass the standard. Even as qualified parts, they are far from meeting the technical requirements for ball quality. The other is the ball welded with multiple plates, but it is not suitable for batch production because of many welds and complex process. Our method is to replace the traditional welding method with the once forming technology of pipe cold extrusion for the sphere of DN 100. At present, there are also pipes for forming in China, but the traditional method they use abroad is the hydraulic expansion molding process, which is complex and inefficient. For the production of large balls, we have also found out a different processing method, called plate forming process. This method is used to reduce the dead weight of the pneumatic ball valve and extend the service life of the pneumatic ball valve. The utilization rate of steel is up to more than 60%, almost double the original one. The net weight of the ball after balling is reduced by more than 50%, and there is only one weld, At the non critical non mating surface. It is not difficult to see that the use of thin wall ball and hollow ball technology is not desirable. This not only improves the low-pressure sealing performance, but also extends the service life of pneumatic ball valves. At the same time, the metalworking hours are reduced by more than 2/3 compared with the original.

Manufacturing and consumption process of pneumatic butterfly valve
Hydraulic machining of pneumatic butterfly valve is a common process for forming annular bellows with circular, elliptical, rectangular, runway shaped sections. After adjusting the relative position of the die and the tube blank, pressurize the inner cavity of the tube blank, and then stop the mechanical tightening along its axial direction. A corrugated pipe of a given length will soon be formed. This is a method of hydraulic forming, called multi wave one-time forming method. This processing method is often used for bellows commonly used as elastic elements. However, for the bellows as the body of the pneumatic butterfly valve, this method will not work. The longer the bellows request, the better. For this reason, people invented another method of hydraulic forming, namely single wave continuous forming method. It can continuously form tens, hundreds, even thousands, tens of thousands of corrugations when the length of tube blank allows. When used, it can be cut according to the required length or the required number of corrugations. In this sense, it can replace multi wave one-time forming machine tools. The bellows of different specifications can be consumed only by changing the molds of different specifications. It can be said that the single wave continuous forming machine tool is a multifunctional equipment for processing corrugated pipes and a key equipment on the consumption line.
1、 Single wave continuous forming method
The working procedure of metal bellows single wave continuous forming is as follows.
（1） Close the upper and lower symmetrical pushing dies! At the same time, move vertically to the axis line of the tube blank in parallel with the die sheet, and tightly wrap the thin-walled tube blank $installed on the mandrel # from the surface.
（2） The mandrel sleeve of the inlet mandrel moves to the left against the friction resistance of% of the seal ring and the inner wall of the tube blank, so that the seal ring fixed on the mandrel moves relative to the mold piece to the preset position.
（3） The working fluid of filling pressure liquid flows from the central hole of the mandrel to between the two sealing rings and acts on the inner wall of the tube blank. Under the action of liquid pressure, the tube blank between the two sealing rings bulges, forming an initial wave.
（4） Push the mold and push the mold against the resistance of the spring&, move it to the right along the guide slide bar, so that the height of the original initial wave increases and the width decreases until the design size