| Blade is a typical hard to machine curved surface part made of superalloy or titanium alloy.As one of the most important parts of aero-engine,the working environment of blade is usually high temperature,high pressure and high speed.The profile accuracy and surface quality have a significant impact on the aerodynamic performance and service life of aero-engine.No matter fan blade,compressor blade or high-pressure turbine blade,there are many characteristics,such as complex surface shape,difficult material processing and high machining accuracy requirements.Obviously,grinding and polishing become an important means of blade finishing.Because of the bad working environment,the influence of human factors and the poor uniformity of blade surface after grinding and polishing.There are some problems in the grinding and polishing of machine tools,such as high cost,small working space and poor universality.The robot has many advantages,such as good flexibility,low cost,high precision of repeated positioning,rich information of sensing mode,etc.,so the grinding and polishing of blade robot has gradually become a new way and hot issue of blade grinding and polishing.In this paper,the theory and technology of robot grinding and polishing of aeroengine blades are studied.First of all,a robot grinding and polishing system including machining,automatic control,detection and other systems is built.Then,the material removal rate of titanium alloy blade was studied on the grinding and polishing system,and the material removal rate model of titanium alloy blade was obtained.Last but not least,the blade surface is planned for grinding and polishing.Finally,the corresponding software of robot blade grinding and polishing is developed,and the practicability of the software is verified by the blade machining experiment.The main work of this paper is as follows:（1）Study on the material removal rate of grinding and polishing based on material removal profile.By combining Preston equation and elastic Hertz contact theory,the formula of material removal rate is extended,and the expression of material removal profile is obtained.The Taylor expansion is used to simplify,and the quadratic curve expression of material removal profile is obtained.Through the experimental verification of the removal profile,the conic fitting error is less than10-3mm,and the experimental results verify the accuracy of the expression of the material removal profile,which provides an important basis for the accurate prediction of material removal.（2）Blade path planning and post-processing based on equal arc length method.The equal arc length method is adopted for the step length of the horizontal and vertical grinding paths.Based on the equal residual height method,the calculation formula of the line spacing of the horizontal and vertical grinding paths is extended,and the factors affecting the line spacing planning of the horizontal and vertical grinding paths are obtained.Based on the planning formula of the distance between the horizontal and vertical grinding,the coupling tool path of the blade inlet and exhaust side grinding was planned.This method overcomes the over cutting problem of the air inlet and exhaust edge grinding by using the cross grinding path and the transition discontinuity problem of the air inlet and exhaust edge grinding by using the longitudinal grinding path,and provides a new idea for the grinding and polishing of the air inlet and exhaust edge of the blade.（3）Development of off-line programming software for robot.The software integrates the forward and inverse kinematics of the robot,the planning of grinding and polishing tool path,and the transformation of Cartesian coordinate system of blade machining points,which is universal to different blades and fixtures.In order to adapt to different robot languages,the software integrates the ability of generating robot simulation code and actual machining code.Therefore,the software can provide guidance for the development of robot polishing software. |
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