Session: CIE-14/15-01 CAPPD: Joint Topics

Paper Number: 141766

141766 - Fast Computation of Collision-Free Cutter Postures Using Discrete Representation of Workpiece Shape 

Simultaneous 5-axis machining enables free change of the tool posture during the machining process. Hence, complex-shaped parts, such as impellers, can be machined while maintaining a short tool length and sufficient clearance between the tool holder and the part without changing the mounting. Machining accuracy and reduction of the machining costs can be simultaneously improved using this method. Hence, the use of simultaneous 5-axis machining has increased rapidly in recent years.

Considering the machining with ball end cutters, which are commonly used in simultaneous 5-axis machining, the determination of machining operations can be divided into two steps: calculation of a cutter path of the tool center and determination of the tool posture at each position along the path. The former can be accomplished relatively easily using offset geometry in which the part shape is expanded by the tool radius. However, the latter requires a complex calculation of safe tool postures that do not cause tool interference or collisions and selecting the optimal posture for the machining conditions from among the safe postures.

This study reports on developing a novel method to quickly calculate safe tool postures. The problem of safe posture calculation can be further divided into two categories: avoidance of gouge where the cutting edge of the tool cuts into the part shape and avoidance of collision between the tool holder and the workpiece. The current study deals with the latter, i.e., collision avoidance between the tool holder and the workpiece.

As machining progresses, excess material is removed, and the workpiece shape becomes smaller. Therefore, the tool holder and workpiece are less likely to collide, and the range of possible tool postures is increased. However, incorporating such a tool posture “margin” into calculating machining commands has not yet been realized. The workpiece shape in the machining process can be computed using a geometric machining simulation. This study considers a technology for generating machining operations integrated with machining simulation and aims to realize a computer-aided manufacturing (CAM) software for simultaneous 5-axis machining that considers changes in the workpiece shape.

In the simultaneous 5-axis machining simulation, discrete methods, such as voxel or dexel models, are commonly used to represent the workpiece shape. As a basic technology required to realize CAM software with built-in machining simulation function, a method for high-speed calculation of the safe tool posture without holder collision for such discrete workpiece models is reported here. In this method, the tool shape is also converted to a discrete form in advance. Safe tool postures that do not cause holder collisions are achieved by a simple overlap check between line segments. By utilizing the parallel processing technology of GPU, all safe tool postures can be calculated in less than 100 ms per machining point.

Presenting Author: Masatomo Inui Ibaraki University

Presenting Author Biography: Masatomo Inui is a professor in the Department of Mechanical Systems Engineering at Ibaraki University, Japan. His current research interests include geometric modeling and its application to the automation of mechanical manufacturing. Inui received his doctorate in precision machinery engineering from the University of Tokyo. He is a member of IEEE and ASME. Contact him at masatomo.inui.az@vc.ibaraki.ac.jp.

Authors:

Masatomo Inui Ibaraki University
Nobuyuki Umezu Ibaraki University