Session: 16-01-01: NSF-funded Research (Grad & Undergrad)

Paper Number: 76777

Start Time: Wednesday, 02:25 PM

76777 - Efficient Feedrate Optimization Method for Spline Toolpath Based on Typical Characteristics of Integral Impeller 

As a relatively complex part of aero engine turbine blades, integral impellers are widely used in major engineering fields such as aerospace, automotive energy, national defense power. In actual milling processing, its complex space, high steepness, and distortion characteristics are important for 5-axis numerical control. Processing puts forward special requirements, and higher and higher requirements are put forward for processing efficiency and processing quality. With the rapid development of electronic information technology, Non-Uniform Rational B-Splines (NURBS) can exactly and concisely express any free-form curves in a uniform way. Due to the superiorities of NURBS in expressing complex curves. The computer-aided design and Manufacturing (CAD/CAM) system can express the contour of the part as a trajectory with double NURBS curves, which is controlled by a 5-axis computer numerical control (CNC). However, in the actual machining of the NC code of the integral impeller expressed by the double NURBS curve, without affecting the machining quality and accuracy of the large curvature area, the feed speed on the path is adjusted reasonably and steadily to improve the machining efficiency of the integral impeller. It is the difficulty of research in this field. Traditional algorithms usually generate NC code trajectories through kinematic constraints to generate a speed curve that meets the motion characteristics of the machine tool. According to the speed curve, the trajectory is discrete and output to the servo control system based on the interpolation cycle to control the motion of the machine tool. This is different from traditional algorithms. When carrying out speed planning, the typical characteristic parameters of the integral impeller in CAM are introduced, and a direct interpolation algorithm for double NURBS curves based on the typical characteristics of the integral impeller is proposed to realize smooth and efficient processing of large curvature areas. First, divide the characteristics of the integral impeller. Because the curvature of the surface of the impeller disc and the back surface of the integral impeller changes relatively smoothly, and the edge curvature of the inlet and exhaust edges changes drastically, CAM is based on the three-dimensional model of the impeller in the actual application process. Based on the above characteristic parameters converted into NC codes that can be executed by CNC, in this study, CNC divides the back of the impeller blade into high-speed machining areas based on this characteristic parameter, and the intake and exhaust edges are divided into low-speed machining areas. Secondly, the high-speed area and the low-speed area after the feature division are discrete with equal arc length based on the interpolation cycle to obtain the high feed speed of the entire curve, and use the FIR filter to smoothly filter the discrete speed to meet the machine tool Finally, based on the speed curve of each motion axis of the FIR filter, the speed in the low-speed area is proportionally adjusted to meet the speed, acceleration, and jerk constraint requirements of the machine tool. Simulation and actual verification show that the proposed algorithm can effectively improve the speed smoothness at the inlet and exhaust edges of the integral impeller, effectively reduce the calculation load of the numerical control system, and improve the overall impeller processing efficiency under the requirement of machining accuracy.

Presenting Author: JianXin Xiao Tsinghua University

Authors:

JianXin Xiao Tsinghua University
Bingran Li Tsinghua University
Jun Fang Tsinghua University
Hui Zhang Tsinghua University