Identification of Milling Information and Cutter-Workpiece Engagement in Five-Axis Finishing of Turbine Blades Based on NURBS and NC Codes

Abstract

Five-axis milling is frequently used for machining of turbine blades. As an inducement of various phenomenon in metal cutting process, cutting force can cause vibration of blades, which will eventually affect the milling accuracy and surface quality. Modeling of cutter-workpiece engagement (CWE) is a key process to predict cutting force, especially for complex tool geometries and workpiece surfaces. In this paper, a method to predict ball-end cutter CWEs for blades with free-form surfaces is presented. The NURBS theory is firstly employed to get the surfaces before and after finishing. Secondly, milling information such as coordinate systems are extracted from NC codes. Thirdly, the CWE boundaries are extracted based on the NURBS surfaces and extracted information. The proposed model is a combination of discrete and analytical method. Finally, the performance of CWE model is examined from computational accuracy and efficiency, and is verified through milling test. The proposed method provides a visualization of complex engagement between tool and blade in five-axis milling process, and may help in five-axis toolpath optimization .

Keywords: CAM, Blade Machining, Five-Axis Milling, Cutter-Workpiece Engagement, NURBS, Toolpath Planning