Session: 03-04-02: Advanced Machining and Finishing Processes

Paper Number: 113134

113134 - Research on Optimization of Sampling Feature Points for On-Machine Measurement of Integral Impeller Blade Profile 

The integral impeller is the core component of the engine. Its blade profile directly affects the fluid movement, and then affects the thrust performance of the engine. Therefore, the blade profile accuracy of the integral impeller is required to be high. In the machining process of integral impeller, five axis milling is an important link to ensure the profile accuracy of blade profile. In the process of five axis milling, there are many factors affecting the final machining accuracy, including machine tool geometric error, blank clamping error, servo following error, machining error caused by unreasonable milling process parameters, machining error caused by tool wear, machining error caused by machine tool vibration and so on. These errors have their own independent modeling and prediction algorithms and compensation methods. However, due to the complex error influencing factors and inaccurate forward modeling, high-precision and efficient error compensation cannot be realized.

The information of the machined impeller profile can be obtained by on-machine measurement, and the comprehensive error distribution of the machining area can be obtained by comparing with the original model. Based on a certain algorithm, the tool path NC program is adjusted adaptively to realize the adaptive compensation of comprehensive error. This method is different from the traditional idea of independent modeling and compensation of each error source. It regards all error sources as one input, does not explore the influence mechanism of contour accuracy, and only cares about the influence results of contour accuracy. It can realize high-precision and efficient comprehensive error compensation.

In the process of comprehensive error adaptive compensation, how to establish a comprehensive error compensation model suitable for the impeller surface combined with the structural characteristics of the impeller is the key problem affecting the machining accuracy after compensation. Huang adopts the tool envelope calculation method for the side milling compensation of ruled blade, which is essentially equivalent to the ICP mapping algorithm with linear constraints; Bi aiming at the large curvature thin-walled part of aircraft skin, combined with the characteristics that the normal deformation is much higher than the shear deformation, an ICP algorithm based on isometric constraint is proposed; For thin web, Du adopts Mart machine learning to establish implicit mapping relationship. All the above are aimed at each workpiece, combined with unique structural characteristics and additional corresponding constraints to establish a rigid ICP mapping relationship.

In this paper, taking the integral impeller as the research object, considering that the on-machine measurement point cloud is distributed on several section lines of several blades, the rotation angle constraint is added in combination with the rotation characteristics of the impeller, the isometric constraint is added in combination with the parallel characteristics of the section lines, and the pitch correction is added at the same time to form three constraint condition groups based on the impeller structure. The optimal matching mapping model between theoretical trajectory and actual machining trajectory is established. Based on this model, the tool path that should be input is inversely solved according to the expected theoretical trajectory, and the adaptive compensation machining of impeller profile comprehensive error based on on-machine measurement is realized.

Presenting Author: Weishu Song Tsinghua University

Presenting Author Biography: Ph.D candidate of Tsinghua University, Department of Mechanical Engineering. The main research direction is machine tool geometric error calibration and on-machine measurement.

Authors:

Weishu Song Tsinghua University
Bingran Li Tsinghua University
Peiqing Ye Tsinghua University
Weihua Chen Tsinghua University