The Whirling Theory And Its Use For Rotors' Machining Of Twoin-screw Pump

The screw pump is a new type of industrial pumps. There are many types of screw pumps to fit for different situations.2G-A twin-screw pump is a not-fully sealed type of screw pump, which could be used for handling fluids with abrasives. It is extremely rugged and highly reliability. Consequently, it's used very widely. The screw pump use one or several screws to move fluids, so the exact design and high precise machining of the screw result in good performance of the screw pump. This paper is wrote about these two aspects.The helicoids of screw are generated by the screw profiles on a cross-section with a screw motion along its axis, so the profile is investigated firstly. The screw profile of 2G-A twin-screw pump is more complicated than other type of pumps, the theoretical equations of the screw cross-section profiles and the meshing line of the two rotors are derived by using gear meshing theory, according to its forming principle. A program is also designed by MATLAB GUI toolbox to calculate the coordinate of cross-section profiles, axis section profiles and normal section profiles, to generate the data file of coordinate points.The rotors of screw pumps are commonly machined using shaped milling cutter. In this paper, a method called whirling is described to manufacture screws. Firstly the principle of whirling processing is analyzed, the mathematical model of whirling is given, and then the method to calculate the exact cutter profile is derived. The contact line between the tool and the workpiece is then determined, based on the equations of the cross-section profile, calculated the profile by MATLAB. A 3D model of the cutter is established by SolidWorks.With customization of SolidWorks, a program is established for creating 3D model of the central rotor or idler rotor. The whirling process is simulated to check its feasibility and accuracy. The experiments are carried out in a modified lathe. The results show that the whirling process could simplify the process of rotors' production, could reach the requirements of semi-finishing and improve the efficiency greatly. In practice, the finishing process can be achieved by improving the design of whirling head and the design of a special machine for whirling.