| As the key component of aeroengine,the blade machining quality has a very important influence on the service performance of the whole machine.However,in order to meet the aerodynamic characteristics and working environment requirements,blade parts usually have the characteristics of thin wall,large twisted blade body and complex profile,which undoubtedly increases the difficulty of machining and manufacturing,and seriously affects the processing accuracy and surface quality of blades.Usually,after forging and NC milling,the blade blank is processed by grinding and polishing to improve its surface integrity and ensure its shape accuracy.At present,the precision machining methods of blades are mainly manual grinding and CNC grinding.Manual polishing not only has high technical requirements and low grinding efficiency,but also has bad working environment.CNC grinder grinding is of high cost and poor versatility.Robot abrasive belt grinding has many advantages,such as high efficiency,good flexibility,easy combination of various external sensors to improve the processing quality,and has been gradually applied to the precision grinding of blades.However,many technical difficulties need to be solved urgently,and grinding process is one of the key technical difficulties.Therefore,this paper carries out research on precision abrasive belt grinding process of aero-engine blades based on grinding platform built by force-controlled robot.The main research contents are as follows:(1)Set up the platform of robotic abrasive belt grinding processing system.The overall composition of the robotic abrasive belt grinding processing system is studied,and the system is divided into hardware and software.The equipment,software and functions of each component are introduced in detail,including HSR-JR605 six-axis industrial robot,Hebson HPS-FT060 six-dimensional force/torque sensor,belt conveyor,belt,Inter Robot,etc.The constant force control scheme adopted by the robot is also introduced.(2)Research on surface roughness of workpiece grinded by abrasive belt.Based on the material removal mechanism of single abrasive particle,the surface roughness prediction model of workpiece in abrasive belt grinding is obtained by using the surface roughness meaning and the undistorted chip thickness model.For the calculation of contact length in the model,considering the characteristics of abrasive belt grinding comprehensively,the elastic deformation of contact length in the grinding contact area is accurately calculated with the known normal contact force and the Hertz contact theory,and the actual contact length is obtained.The surface roughness prediction model is simulated and analyzed with MATLAB software to determine the influence of various parameters on surface roughness.(3)Parameter optimization and experimental verification of abrasive belt grinding of blade robot.According to Preston equation,the process parameters affecting the material removal rate are determined,and then the grinding parameters affecting both the blade surface roughness and the material removal rate are determined by combining the above research results of surface roughness.It is verified by single factor experiment and reasonable range of each parameter is determined.On this basis,the center composite design(CCD)experiment is carried out,and the width learning system is used to train and fit the experimental data to obtain the prediction model of surface roughness and material removal rate,and the accuracy of the model is verified.Then,the prediction model of surface roughness and material removal rate is used as the objective function to optimize the grinding process parameters,and the optimal combination of grinding process parameters is obtained by using multi-objective particle swarm optimization(MOPSO).Finally,experiments were carried out on titanium alloy test blocks to verify the validity of the optimal parameter combination.(4)Research on Optimization of normal contact force variation in robot abrasive belt grinding.In view of the problems that are easy to appear in blade robot abrasive belt grinding,such as overcutting and under-cutting in the cutting in and out stage,poor grinding effect in places with large curvature change,it is found that the main reason is the change of normal contact force.In order to solve the effect of such problems on the surface quality of the blade after grinding,an adaptive technology of process parameters based on the change of normal contact force is proposed,and the effectiveness of the technology is verified by grinding experiments of titanium alloy test blocks.Finally,the final processing of the blades is carried out,and the experimental results show that their processing quality and processing efficiency have been significantly improved. |
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