Research And Development Of Computer-aided Design System For Grinding Wheel Of Screw Rotor

Screw compressors are widely used in various industrial sectors due to their obvious advantages such as energy conservation,high efficiency,high reliability and low noise level.Its market demand will far exceed that of traditional compressors and has even started to replace traditional compressors in many industries.Screw rotors--the core components in a screw compressor,the processing quality of the screw rotor directly determines the overall performance of the screw compressor,and the main ways of machining the screw rotor are: milling,hobbing and grinding.Among them,grinding has become the main way of machining screw rotors because of its high efficiency and precision.In the actual production of screw rotors,most manufacturers use the form of discrete point data to express the end profile of screw rotors,which is composed of multi-segment tooth curves.However,in the process of solving the profile of formed-grinding wheel,the first derivative at the data point of rotor end profile must be obtained first.The solving process of the first derivative satisfying accuracy is not only tedious,but also very difficult,and the solution accuracy of the first derivative also affects the smoothness of the profile of the formed-grinding wheel.Under this background,this thesis focuses on the subject of "Research and Development of Computer-aided Design System for Grinding Wheel of Screw Rotor",and develops a computer-aided design system of the formed-grinding wheel for machining screw rotors.The main research contents are as follows:(1)The basic structure and related characteristic parameters of screw compressor and screw rotor are analyzed,and the three-dimensional model of screw rotors is established.(2)Based on the envelope method,the mathematical model of contact condition between the screw rotor and the formed-grinding wheel is established.The Simpson numerical differential method is used to solve the first derivative of the data points of the end profile in the contact condition equation.The Simpson numerical differential method overcomes the technical problem of low derivative accuracy at the first and last points in the traditional derivative calculation.This method of derivation is of great significance for improving the design accuracy of the profile of formed-grinding wheel.(3)This thesis analyzes the adjustment of screw rotor end profile in the profile design of formed-grinding wheel and the post-processing problem of the profile design of formed-grinding wheel.For the problem of outliers in the profile of formed-grinding wheel obtained by numerical calculation,a robust locally weighted regression method is proposed to smooth the profile of formed-grinding wheel.The error between the profile of formed-grinding wheel after smoothing by robust locally weighted regression method and the enterprise provides the profile data of formed-grinding wheel for actual processing are analyzed to verify the feasibility and correctness of this smoothing method.(4)Based on the theory of the profile design and post-processing of formed-grinding wheel,the formed-grinding wheel computer-aided design system is developed.This system mainly includes five design functions: import of the rotor end profile data,increment and derivation of the rotor end profile data,input of rotor parameters and formed-grinding wheel parameters,angle adjustment of the rotor end profile and solution and preservation of profile data of formed-grinding wheel.And it also includes four post-processing functions: manifest special points,automatic and manual removal of the special points,automatic and manual replacement of the special points and smoothness of formed-grinding wheel profile.(5)Based on the Vericut virtual machining simulation software,the three-dimensional model of the five-axis CNC rotor grinder is established.And the virtual grinding scene of a certain type 6-tooth female rotor is built with the formed-grinding wheel designed by the development software of this project.Finally,the virtual grinding process simulation of the female rotor is completed,and the accuracy of the profile design of formed-grinding wheel is verified.(6)A formed-grinding wheel is manufactured based on the designed profile of formed-grinding wheel,and a certain type of 6-tooth female screw rotor is ground with the manufactured formed-grinding wheel on a KAPP five-axis CNC rotor grinder.Then,the precision of the ground female rotor is measured with coordinate measuring machine.The measurement results show that the designed formed-grinding wheel could meet the practical industrial application,and the practicability of the developed computer-aided design system for formed-grinding wheel of screw rotor is verified.