Online Mesurement Planning And Error Compensation Of Impeller Flank Machining Based On Spherical Envelope

Complex thin curved surface parts such as integral impellers are widely used in the field of aerospace, marine and others, but the blade is thin and the tunnel is narrow, it is a "difficulty" in the machining field. Five axis CNC milling machining efficiency is high, which is one of the common methods for machining integral impeller. However, due to the effect of several kinds of factors such as elastic deformation, vibration and friction of impeller blade, there exist machining errors and restrict machining precision of integral impeller. Therefore, machining error measurement and compensation of thin wall parts such as integral impeller is an important method to improve the machining accuracy, class integral impeller machining errors of thin-walled parts measurement evaluation and compensation is an important method to improve machining accuracy. The measurement accuracy of traditional coordinate measuring machine is not high because of the positioning clamping and some other human factors, on-line measurement is widely used in recent years, the errors brought by repeated clamping can be avoided and the accuracy is high.Five axis flank milling of integral impeller, the errors are not only caused by elastic deformation and other external factors, but also there exists principle error due to the formation of flank milling is tool envelope surface. Therefore, how to measure and compensate the actual processing errors is an issue of great research significance.Firstly, this paper arranges the achievements of research group in the past, such as the tool path planning method of flank milling complex curved surface and the representation of tool envelope surface, which is theoretical foundation of the later research work in this paper.Secondly, according to the characteristic of flank milling complex surface, in order to adjust flank milling cutter location to reduce the machining error, the integral impeller blade flank milling tool position are analyzed and optimized in this paper. According to the principle that points from cutting tool tangent to surface is consistent with measuring ball tangent to surface, put foward a method of on-machine measurement path planning for impeller blade based on spherical envelop theory. The discrete points of the flank milling cutter axis are obtained by offset, compensating the machining errors to the corresponding tool axis discrete points based on mirror compensation method, then using least square method to generate the new flank milling tool position.Finally, the experiment project that machining and online measurment of integral impeller is designed. The integral impellers are separately processed by the NC program which are generated by the tool position before and after compensation, measuring the errors of impeller blade, the measurement results verify the correctness of the online measurement planning and compensation method based on spherical envelope, the machining error of impeller is effectively controlled.