A Multi-Scale Tool Orientation Generation Method for Freeform Surface Machining with Bull-Nose Tool

Abstract

Free-form surface parts are widely used in industries, and they consist of intricate 3D surfaces such as molds, impellers, and turbine blades that possess complex geometrical contours and demand high precision. Proper tool orientation is crucial for ensuring the efficiency and accuracy of five-axis computer numerical control (CNC) machining. Multi-scale methods have received much attention and have been widely used in various fields. They have been proven to be instrumental and can obtain fruitful outcomes. Ongoing research on multi-scale tool orientation generation methods, which aim to acquire tool orientations that satisfy both macro- and micro-scale requirements, is significantly important for improving the machining quality of workpiece surfaces. This paper proposes a multi-scale tool orientation generation method that considers both the machining strip width and roughness scales. This method also ensures a smooth tool orientation and avoids interference in the machining process. First, the correlation between the tool orientation and rotational axis is analyzed, and feasible area calculation and tool orientation adjustment methods are introduced. Then, the paper introduces the calculation method for machining strip widths on the macro-scale and the roughness calculation method on the micro-scale. Besides, tool orientation adjustment methods for both scales are proposed. Next, a multi-scale tool orientation generation method is developed to generate tool orientations that meet the macro- and micro-scale requirements. Finally, to verify the effectiveness of the proposed multi-scale tool orientation generation method, it is applied to the machining of a free-form surface. Experimental verification results have shown that the tool orientation generated by the proposed method can obtain the expected machining strip width and roughness, meeting both macro- and micro-scale requirements. Therefore, this method has significant potential for engineering applications.

Twin-Tool Orientation Synchronous Smoothing Algorithm of Pinch Milling in Nine-Axis Machine Tools

“…Once the knot vector S and control points a i have been determined, the B-spline curve P c (s) of the tool axis can be obtained from Equation (14), which is called the tool posture curve P c (s), and describes the trajectory of a particle on the spherical surface, representing the angle variation of the tool axis vector at the contact point. Therefore, new tool axis vectors are interpolated the contact point along the tool path; all tool axis vectors are located on the tool posture curve, and the global smoothing tool axis vector can be obtained.…”

“…Hong et al [ 13 ] described a practical method for tool orientation generation for ball cutters commonly used in complex-surface-finish machining. Dong et al [ 14 ] proposed a multiscale tool orientation generation method that considers both the machining strip width and roughness scales. Sun et al [ 15 ] presented the prediction of an automatic tool axis orientation algorithm that avoids chatter while improving productivity.…”

Selected Aspects of Precision Machining on CNC Machine Tools

“…In practice, CAD model continuity leads to a surface deviation that can vary up to 60 µm but does not affect surface roughness [15]. Dong et al reported that the surface roughness of the freeform surface when milling is greatly influenced by the bull-nose mill's local inclination angle and tilt angle [16]. Though 3D scanning is a reliable measuring method, it requires expensive equipment.…”