Research On Disposal Of Interference In End Milling For Multi-axis NC Machining

The management of interference, including interference-checking and interference-avoiding, is an inevitable problem in CAD/CAM system. This paper presents algorithms for solving interference in end milling.Workpieces with the cutter location points on the same plane are usually milled by window-frame method by 2-axis NC machining with flat-end mill. Direct offset method is an important way for toolpath generation. In terms of the properties of profile, pocket, islands and pocket with islands, the phenomenon whether the offsetting curves are included or not is analyzed. To generate interference-free toolpath, some improvements shall be added to direct offset method, and a new algorithm for arbitrary planar shapes is presented.Considering three-axis NC machining for sculptured surfaces and by discretizing the surfaces into triangle mcshss, a new interference-checking algorithm is researched in this paper. Meanwhile, to avoid the interference in three-axis machining, the main spindle must lift up with the minimum distance. Formulae for the calculating are proposed concisely according to ball-end mill, flat-end mill and fillet-end mill respectively.This paper also presents a method to managing interference of sculptured surfaces for five-axis machining. This interference can be avoided through lifting or swinging the spindle. Accordingly, algorithms and formulae are proposed to calculate suitable swinging angle or minimum lifting distance inthe case of ball-end mill and flat-end mill respectively. The algorithm for ball-end mill can solve the problem of zero-speed, while the algorithm for flat-end mill avoids interference by swinging the spindle firstly, which also takes into account of inference-avoiding, precision requirement and machining efficiency.The proposed methods are concise and adapted to various kinds of workpieces, but need a little more computer memory to save the inevitable data. However, nowadays the memory capacity of NC machining tool has been improved so greatly, the proposed methods are feasible for modern manufacturing.