Research On Plunge Milling Method With Fixed Rotating Axis Of Closed Impeller

In order to remove material quickly at the stage of rough machining of a closed impeller, the theoretical model of the plunge milling of an impeller with fixed rotating axis is summarized as an optimization problem of finding the maximum volume of the inscribed general cylindrical surface of the impeller’s tunnel surface. And then the optimization model of finding the maximum projected area of the cylinder along the tool axis direction is proposed, in which the polygonal area is used as an approximate substitute of the projected area to reduce the computational difficulties.To solve the theoretical model, the discrete spatial line segments are used as an approximate substitute of the blade ruled surfaces and the discrete spatial arcs are used as that of the hub and shroud surfaces of revolution. The maximum projected area optimization problem is solved by MATLAB Optimization Toolbox, obtaining the maximum projected area and directrix of the inscribed general cylindrical surface.Considering the distortion property of the narrow and long tunnel, the principle for determining two segments of the impeller tunnel when machining from both sides of the closed impeller is proposed. That is, the goal is to get the value of parameter u when the two inscribed general cylindrical surfaces of the two tunnels of the impeller have its maximum volume. A series of values of parameter u are calculated, and then in which the one with maximum volume of two tunnels is adopted.At last, the correctness of these methods is verified by an impeller with a wheel diameter of 400 mm and 17 blades.