Optimal tool orientation generation and chip volume/cutting force predictions for 5-axis CNC machining of curved surfaces using flat-end mills. Issue 3 (16th April 2017)

• Record Type: Journal Article
• Authors: Luo, Shan; Dong, Zuomin; Jun, Martin B.G.
• Is Part Of: Computer-aided design and applications. Volume 14:Issue 3(2017)
• Page Start: 331
• Page End: 342
• Publication Date: 2017-04-16
• Subjects: 5-axis CNC -- tool orientation -- EMS -- tri-dexel -- free-form surface -- flat-end mills -- chip volume -- cutting force; Computer-aided design -- Congresses; Computer-aided design -- Periodicals; Engineering design -- Data processing -- Congresses; Engineering design -- Periodicals; 620.00420285
• DOI: 10.1080/16864360.2016.1240454
• Languages: English
• ISSNs: 1686-4360

Abstract

ABSTRACT: Machining using a flat-end mill with varying and optimal tool orientations and feed-rate is an ideal approach to reach the full potential of 5-axis CNC milling of curved surfaces. Rotating the flat-end mill with different tilt angles can produce different effective cutter curvatures at the cutter contact point (CCP), improving machining efficiency and surface quality with better cutter-workpiece curvature match, and avoiding gouging for concave surfaces. This CCP-focused approach, if combined with globally optimized CNC tool path and the optimal feed-rate determined by the constraining instant cutting force, present a systematic approach to optimize 5-axis CNC machining. However, this approach also presents significant challenges due to the complex tasks of modeling varying cutter and part surface geometry/interaction. This research is aimed at solving the stated research problem. Several new methods have been introduced for optimal tool orientation generation and for instant cutting chip volume and forces calculations. An optimal tool orientation generation method based on the combination of the surface normal method for convex curved surfaces and Euler-Meusnier Sphere (EMS) method for concave curved surfaces has been introduced to achieve the maximum machining efficiency and surface quality. A Non-uniform rational basis spline (NURBS) surface with concave, convex, and saddle features is used to demonstrate these newly introduced methods. After the optimal tool orientation is established, a Tri-dexel workpiece model is used to predict instant material removal rate and cutting forces by updating the machined workpiece and subtracting the cutter-workpiece engagement zone, to ultimately identify the maximum allowable feed-rate and depth of cut. The complex approach is verified separately at present. The geometry of the tool paths and machined surface was validated using machining simulations. A simplified cutting experiment using a 3-axis micro-milling machine is conducted to verify the predicted chip volume and cutting forces on a flat surface using a constant depth of cut and the pocket toolpath, and cutting force predictions are in good agreement with the measured data both in magnitude and trend if the runout effects are ignored. GRAPHICAL ABSTRACT: