The Online Dressing Method Of Grinding Wheel For Screw Rotor

The screw rotor grinding technology is matured in abroad at present, as well as the grinding machines. In China, the technology is in the study stage. Few screw manufacturers afforded high price to import the foreign machines, and only method of its application was grasped but its key technology. As far as know, there is few with respect to the core technology of screw rotor grinding in the public literatures. Grinding machining is efficient for enhancing rotor surface accuracy and performance of screw compressor; hence, it is significant of the localization of screw rotor grinding technology and equipment. As one of the critical technology in the research of screw rotor grinding, the dress method of grinding wheel is urgently awaits to be solved.In this paper, the method for wheel dressing was studied on the basis of analyzing of screw rotor grinding process. A conjugate model and a method for determining the cutter (grinding wheel) geometry to ensure sufficient precision for grinding a screw rotor (workpiece) is presented. With the conjugate model, the cutter geometry parameters can be determined from the tooth profile of the work piece, vice versa. The cutting parameters include the distance and position angle between the centerlines of the cutter and the work piece. To consider the effect of cutter wear on the grinding precision, the tooth profile in the transverse plane is measured at the end of a rough, or semi-finish cut for each tooth profile; the cutter geometry is obtained from the conjugate model; machining error of the tooth profile and allowance for finish are then determined. In the subsequent grinding, the processing parameters are determined from the rotor error evaluation and compensation approach, which compensates the amount of cutter wear resulted in the previous cut. If the amount of the adjustment to the center distance and angle exceeds the threshold, optimal parameters with minimal amount of grinding wheel dressing are pursued to prolong the cutter life. The proposed methodology is programmed into a computer program written in MATLAB. Numerical results obtained from the program show the validity and feasibility of the proposed method.The online grinding wheel dressing method and its software, which are presented in the paper with fully consideration of the engineering practice, are expected to communicate with CNC system of the grinding machine, to grind the screw rotor and control its precision.