Analysis And Research On Error Of Manufacturing Complex Thin-walled Blade Surface

Complex thin-walled surface is widely used in aeronautic and aerospace industries, and also in ships building industries; so far, NC (Numerical Control) milling has become the most important way in the manufacturing. In comparison with the traditional way, NC milling has high efficiency and good quality; however, machining error which is caused by the deformation seriously influences the accuracy and the surface quality of blade. Thus, the prediction and compensation for the blade surface become the most effective method to reduce the the machining error.This paper firstly researches on the cutting forces which exist in the finish milling of blade, afterwards designs the orthogonal experiments which can get the related coefficient of the experimental formula, and studies the iterative algorithm of the deformation, and then compensates the surface error, finally the actual machining experiment is done. Through comparison with the ideal surface, the quality and the accuracy of the compensated blade has greatly improved.The main content is as follows:1. The blade surface is modeled based on the theory of B surface. Use UG to model the whole centrifugal impeller, and then the tool path for rough and finish machining of the blade and the flow is generated by UG software. Afterwards, the contact points of the tool path are calculated, and then the normal vectors of the blade surface are gotten by programming. All above are prepared for the analysis of the blade deformation.2. The modeling for the milling force of the ball end mill is performed. Firstly, the model of the mill force based on integral principle is contrasted with the model based on experimental formula. Based on the needs for deformation analysis, the later was chosen. Afterwards, the test for calculating the cutting force coefficient is designed, and then the model of cutting force is gotten.3. Based on the experimental model in the second step, the cutting forces are calculated in different cutting conditions. The coupling effect between the cutter force and the blade deformation is analysis when the cutting process is going on. After that, the flow of the deformation analysis is designed, and then the iterative algorithm for the blade deformation and the cutting force is performed by the language of MATLAB, and then, integrate the algorithm and the ANSYS for the iterative analysis, and the process won't be terminated until the setting precision is reached. After all, the final cutting force, cutting depth and deformation of all the contacted points are gotten. All of these are prepared for the compensation of the program.4. Study the method of the compensation error, and give out iterative algorithm which is used to calculate the final deformation of blade surface, then the amount of compensation is calculated to get the new contact points'trajectory, thus the distortion compensation is finished.5. Carry out verification process by manufacturing the whole impeller. Generate the post-processing procedures for double turntable 5-axis CNC, and then simulate the NC codes by VERICUT. Respectively use the original NC codes and the compensated NC codes in the blade surface finish machining.Collect the points' data of the blade surface which has been compesated, and measures them by 3D dimensional scanner, then analyze the surface differences with the original blade surface by using IMAGEWARE, and then calculate the error, finally verify the methods'correctness.