A double-NURBS approach to the generation of trochoidal tool path

Abstract

Trochoidal milling becomes a popular strategy in high-speed rough milling, thanks to its advantages in lowering cutting force (and tool wear) and increasing tool life. However, it also suffers from the disadvantages of low cutting efficiency and prolonged machining time due to its reduced cutter-workpiece engagement in the cutting area and the idle tool path in the non-cutting area. In this paper, a new trochoidal tool path generation method is proposed based on a double-NURBS curve. Unlike traditional circular trochoidal tool path that combines circular and linear paths to approximate the trochoidal path, the double-NURBS tool path can truly represent a trochoidal path with C 2 continuity throughout the entire tool path. In the front cutting area, the control points of the NURBS are modified to increase the cutter-workpiece engagement angles; in the rear non-active area, the NURBS curve is modified to shorten the non-cutting distance and the machining time. Degree elevation of the NURBS circle from 2 to 3 maintains C 2 continuity to ensure the machining is smooth throughout all transitions. Cutting force simulations and pocket machining experiments are carried out to validate that the proposed double-NURBS approach deliver the expected result and performance.

Effects of Toolpath Parameters on Engagement Angle and Cutting Force in Ellipse-Based Trochoidal Milling of Titanium Alloy Ti-6Al-4V

“…Jacso et al [15] developed a B-spline-based toolpath-generating algorithm for trochoidal milling of straight slots, which can maximize the material removal rate while controlling the cutting load. Chang et al [16] planned a double-NURBS trochoidal toolpath, which can represent the entire toolpath with C 2 continuity. Luo et al [2] proposed a four-axis trochoidal toolpath planning method for rough milling of aero-engine blisks.…”

“…The advantages of trochoidal milling in rough machining can be further enhanced by optimizing the toolpath, such as improving the toolpath continuity [15,16], shortening the toolpath length [2,14,17], balancing the engagement angle and the cutting load [32][33][34][35]. The true trochoidal toolpath has C 2 continuity and can avoid a sharp change in engagement angle and cutting force during the milling process, and this helps to improve the smoothness of machine tool movements [2,36].…”