Computer Aided Design Of Screw Rotor Profile For Grinding

This paper is Supported by the National Natural Science Foundation of China (No.50975038) and National Science and Technology Support Programme of China (NO.2012BAA01B00). Higher quality requirement is put forward to Profile of Helix-Shaped Compressor Rotor(PHSCR) because of the extensive use of digital controlled grinding machining method. It is of significance to study corresponding design method and pre-proccess technology of PHSCR in order to improve its menufacture accuracy and speed in grinding-process.To deal with models of PHSCR given in numerical form, which are figure out by a certain software, parametric cubic spline interpolation is introduced into of the data set, and basic space conjugate theory interrelating to PHSCR is also discussed. Based on those, methods for calculating its key performance parameters are promoted, mathematical model and algorithm given after analyzing the process of profile’s retreatment, and then an software to the design and pre-proccessing PHSC developed.First of all, cubic spline is used to plane curve with numerical form, and then parametric cubic spline is used to improve the result of cubic spline. One example shows the effect of the improvement. Rotor profile conjugate algorithm and space curved surface model are established based on coordinate transformation theory.Secondly, the key performance parameters are calculated based on space curved surface model of the rotors. Length of contact line is calculated by meshing condition and formulas for area between tooth as well as rotors’-used-area coefficients are obtained. Numerical calculating method of leakage-triangle-area is inferred by analyzing the engagement of rotors in space. The calculating method of twist-angle-coefficient as well as output volume is obtained by transforming from volume change between tooth to area change.Subsequently, this paper presents mathematical model and algorithm for every steps of pre-proccessing. Mathematical models for continuity check, probe path check, adding lead-ins and point density and cutter direction adjustment are established respectively by analyzing the requirements for every steps of pre-proccessing to achieve, also the algorithm flow charts are given. The addition and optimization method for clearance as well as tolerance distribution method based on the clearance are presented by taking equidistant-curve method as clearance added method. At last, the computer aided design software for PHSCR based on modular design concept is developed with MATLAB as programming platform. The operational process of the software is demonstrated by example to prove its practical applicabilityThe study of the design and pre-proccessing technology for profile and the computer aided design software will be of reference value and significance to study grinding process of PHSCR deeply.