Shrouded turbine blisk is an important component for liquid-propellant rocket engine, airplane engine and some other high-power turbine machines. It is made from high-temperature alloy (e.g., nickel-base alloy and titanium alloy) and hence, is difficult to machine. In addition, its geometrical shape is complicated involving many semi-enclosed, twisted, free-form surfaces. In order to ensure the best performance, its dimension accuracy is very demanding. For the moment, an effective way to manufacture shrouded turbine blisk is Electrical Discharge Machining (EDM) using form tools (form electrodes). However, owing to its complicated geometry, existing commercial CAM systems cannot generate the interference-free tool path for it. In this paper, a new tool path generation method is presented. The new method is base on the quadratic programming and CNC multi-axis simultaneous control. It generates tool path in two steps. First, a feasible zone is generated by coarse search, which gives an elementary path for form tool feed. Then, within the feasible zone the actual NC tool path is found by fine search through CNC multi-axis simultaneous control simulation. In practice, a form tool follows the interference-free tool path moving into the twisted passages of blisk for machining, while the blisk is turning by a CNC turntable. The new method is validated experimentally. Compared to the existing methods, it can obtain high machining efficiency and high machining accuracy. Experimental results indicate that the new method is accurate. This new method can also be applied to many other machining applications involving complicated geometrical shape.
Tool path generation for milling of free form surfaces with feed rate scheduling
