A Study On Global Tool Positioning Strategy And Its Application In Machining Of Large Paraboloid Antennas

The increasing application of 5-axis machine tools makes the efficient machining applicable. But for years the research on tool positioning strategy were generally influenced by the local contacted method. The cutting band was thus too narrow to make full use of the advantage of a 5-axis machine tool in reducing cutting time and cost. The thesis presented intensive investigations in this area and carried out explorations on fundamental theory and on laboratory experiments. Firstly, some essential studies were undertaken. The envelope theory is the principal concept in studying of sculptured surface machining, but relative research was insufficient especially for the understanding of the character curve application in the calculation of cutter locations. The author analyzed the envelope surface of a torus cutter that was widely used as a general tool, developed a expression for the character curve and named a term of "actual cutting edge of torus". Some important properties of the character curve were also summarized. All these work set up a foundation for the future research. Secondly, global cutting error were analyzed. Because of the limitation of local geometry method, most of fashionable tool positioning strategies were likely to cause global errors. The author took the PAM as an example, explained the two kinds of global errors: Cutting Edge Error and Correlative Error. Corresponding error expressions were also developed, and their influence factors were discussed in detail. The author also pointed out that these two kind errors were global cutting error, and they could not be avoided in any strategies based on local geometry. Furthermore, a new global tool positioning strategy was discussed. Thirdly, a new kind of global tool positioning strategy based on the character curve was developed by the author. By applying "Global curvature fitting rule", the research emphasize was extended from "cutter contact point"to "cutter location error curve". The cutter contact point was only a special point on the cutter location error curve. The expanding of studying scope could cause a more detailed investigation of the relationship between the cutter and...