Surface Modeling And Cutter Location Planning Of Marine Propeller With 5-axis Machine Tools

Marine propeller is a type of free form surface part. Its surface shape and manufacture precision decide a ship's thrust efficiency and noises. The research about manufacture method will help to improve the manufacture precision and efficiency of this type of part. The traditional manufacture method of a propeller is by rough cut with general milling machine plus a mass of manual polish. It is laborious and time-wasting and the precision can't be guaranteed. With the development of NC technology, at present, the machining of a propeller is often finished by a NC machining center with ball-end cutter or flat-end cutter. But the machining precision is not perfect yet. How to take full advantage of the potential of 5-axis machine tools and frank mill the free form surface with non-ball-end cutter to improve the manufacture precision and efficiency of a propeller have been the research emphases of NC machining.On the basis of analyzing the theory of the modeling of the propeller surface, this paper transforms the section data given by design to the data in Descartes coordinates. Interpolates the section data to get enough data and fits the blade surface with the least square method. A perfect C2 blade surface can be obtained by adjusting the deviation weight and fairing weight. According to the cylinder rough, two rough cut methods are preferred. One is similar to pocket machining, and another is by searching points. With the former, the machining area can be controlled easily and can be used in finish cut also. With the latter, the calculation and programming is easy. With differential geometry knowledge, the local characters of the blade surface are analyzed. Based on researching the cylindrical cutter's osculating location, the methods to calculate the osculating location of the conic cutter and the torus cutter are discussed. A method of tool path planning based on the second order osculating method is preferred. With this method, the machining strip can be broadened evidently on precondition of assuring the machining precision and the efficiency is improved. With the modeling and simulation function of UG and Vericut software, the correctness of the propeller's surface modeling and NC machining method is proved.