High Performance Computation of Interference-free Five-axis Machining

• Main Authors: Robert Gian, 簡孟樹
• Other Authors: Alan C. Lin
• Format: Others
• Language: zh-TW
• Published: 2002
• Online Access: http://ndltd.ncl.edu.tw/handle/36882527461675989149

博士 === 國立臺灣科技大學 === 機械工程系 === 90 === ABSTRACT In general, the workpiece that a 5-axis machine cuts are complex parts with undercut geometry, which renders the difficulty of determining interference-free tool orientations. The strategy that most commercial CAD/CAM software adopts is the introduction of points, lines or normal directions to set up initial tool orientations, and then tool collisions are taken care using a trial-and-error method. On the other hand, approaches proposed to solve the problem of tool collision during 5-axis machining can be found from literatures, including visible cones, 2-phase approach, C-space, minimum-distance approach, etc. Those methods suffer from the high-order of computation n3 ~ n4, where n is the total number of cutting points along a single parametric direction. Computational explosion can even be found in some approaches. Therefore, this research proposes an “open-region” approach which proves to be n2 of computation. In this thesis, this approach is not only formally defined, but also geometrically solidified. It is verified in the thesis to solve the most difficult problem found in 5-axis machining — automatic determination and high-performance computation of tool orientations which are free of collision and gouging. In order to achieve the goal of high-performance computation, this research considers the division of the to-be-machined surface into the following two regions: non-undercut region and undercut region. For the non-undercut region, loop orientations are taken into account to automate the determination of cutting tools with various radii for rough machining. As for the undercut region, the proposed open-region approach is applied to find cutter paths which ensure the removal of material in every single path. While in finishing operations of the undercut region, non-parametric cutter paths are firstly planned, and the matching of curvatures between the geometry of flat-end mill and the to-be-machined surface is undertaken to achieve high-precision machined surface. The approach of open-region again is used here to detect any existence of collision between the cutting tool and the workpiece material. In case of any collision, a ball-end mill is used instead to carry out finishing operations. During the operations, proper orientations of the tool spindle are automatically decided based on the open-region approach, together with the use of solid model to detect any gouging at the ball nose of the tool, and the introduction of the so-called “reverse cutting” to avoid the collision between the tool flank and the workpiece material. In addition to proposing the fundamentals and the algorithms for high-performance computation of cutter paths for 5-axis machining, this thesis uses ACIS as the geometric kernel to develop a prototype system. A number of practical examples are also tested to verify the feasibility and performance of the proposed methods for the generation of cutter paths of 5-axis machining which are free of collision.