| As one of the most important part of the internal-combustion engine, piston would be distorted in the special working condition by the heat and force acted on. In order to compensate this distortion, modern pistons with convex contour and vari-elliptical cross-section are designed, which can decrease wear and tear, depress working noises, prolong piston longevity and enhance engine performance. Therefore, machining precision and assembly precision of pistons influence engineperformance greatly. It is valuable to develop a new kind of CNC (Computer Numerical Control) System for automobile industry and airline industry, which canmachine pistons with convex contour and vari-elliptical cross-section.In this paper, a new kind of CNC system to machine shaft with non-circular cross-section is proposed. Pistons with convex contour and vari-elliptical cross-section are most representative examples of non-circular shaft workpieces.A universal precision lathe is rebuilt creatively as the experiment machine. Before software programming and debugging, the control algorithm is simulated with graphic in order to validate its' feasibility.The rebuilt machine, in which characteristic of lathe, feature of milling machine and advantage of explorator are integrated, is a key unit of the system. Unique mechanics designs made this system have larger cutting force, excellent flexibility and nice precision.On compare with other similar NC system, micro-feed mechanism based on a simple cam explorator proposed in this paper, which can offer greater cutting force and more dynamic rigidity than the fine feed servo mechanism based on linear motion actuator or electromagnetic actuator.Besides an rotatable principal axis, this system has a special cutter like a disc which can rotate around its' own axis at high speed. The CNC system proposed in this paper can machine workpiece by turning, milling and grinding, if proper tools are replaced, which shows excellent flexibility.IllOn the basis of special mechanical structure, a new interpolation method between a turning coordinate axis and an linear coordinate axis is proposed firstly. A simple cam outline under affine transformation can fit multiple non-circular carves of revolution. A control method to form vari-section surface is also proposed in this paper. In order to make manipulators use the system software easily, the function of auto-programming is integrated with interpolation module. |
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