Post Process And Interference & Collision Detection In The 5-axis Machining Of Propeller

Propeller is the core part of a ship. The 5-axis NC machining technique is used to improve its machining precision and efficiency, consequently improve the performance of the ship. The thesis researched on the NC machining technique of the integral propeller, the development of specific post-processor and global interference & collision detection which occurred during the machining, combining with the project of lathe-mill machine tool with seven-five axis for propeller.On the basis of analyzing 5-aixs NC machining technique of the integral propeller at home and abroad, the propeller NC machining was researched in the thesis. Main contents include:The integral propeller NC machining technique was discussed and the cutting location was planned according to the character of the propeller surface. Firstly, the surface of propeller was divided into several parts and the principle is that using the standard mill head if there is no interference. Then, the proper cutter was selected, and the stepping over distance and cutting width was set in response to the design requirement of the propeller surface. Finally, the proper axis control method that fits the curvature of the surface was selected, and the 5-axis cutter location was generated.The postprocessor was developed according to the specific structure of the machine tool with seven-five axis. It transformed the cutter location file to NC machining file. During the post process, the programming feed speed of every block was got from the feed speed that is set according to the technique, and then the feed rate can be constant during the machining. The non-linear error was adjusted.A collision detection algorithm based on dynamic hierarchical OBB trees is proposed for the global collision in the 5-axis machining of overlapped area of impeller. Firstly, the OBB trees of impeller and special milling cutter are built, and then the dynamic coordinate transform matrix of OBB tree in every machining position is formed using the theories of multi-rigid body system kinematics. And the collision detection is realized by using the separate-axis theory. Simplifying the machine mold, classifying the OBB trees and judging the relative motion trend improve the efficiency of global collision detection algorithm.The machining process verified the technique that researched in the thesis and the programming method was effective. It solved the programming problem of the propeller and it's very practicable.