A New Strategy of Tool Path Planning Based on Hydrodynamic Data to Machine Marine Propeller

Marine propellers are complex surfaces that are usually machined with a perfect roughness in order not to disturb the theoretical flow. Because this requirement is penalizing from a manufacturing point of view, the global objective of the study is to propose an approach in which the machining parameters are linked to functional properties of the blade in order to remove the polishing phase. To reach this objective, hydrodynamic data are used: streak lines, that are computed during the propeller design phase, characterize the fluid behavior at the close vicinity of the blade. Those lines, which are theoretically continuous at the leading edge, turn out to be discontinuous, due to the computing method. To be consistent with the fluid behavior as much as possible, the idea presented in the paper is to compose a continuous trajectory, especially at the leading edge, to mill the surface. Thus, an algorithm is developed to plan tool paths which are smoothed at leading edge using Bezier curves. Moreover, this algorithm allows to quantify the cusp height at the leading edge to avoid a drop in performance using criteria linked to the dynamical behavior of a five axis machine tool. In this work, a strategy is developed and enables multiaxial milling of a blade surface by using geometric and hydrodynamic data and by respecting the associated constraints.