A NEW STRATEGY OF CAVITY CUTTING TRAJECTORY GENERATION IN HIGH SPEED MACHINING

摘要

High speed machining is widely used in manufacturing. For its high cutting speed, high feeding rate, and high machining accuracy, its requirements for cutting trajectory in high speed machining are so strict that only continuous and smooth trajectories with even cutting loads can lead to high machining efficiency and accuracy. The traditional row or ring machining trajectory fails to meet these requirements. In order to acquire the continuous and smooth machining trajectories, and to avoid load mutation in the machining process, some researchers developed a curvilinear cutting trajectory generating method based on partial differential equation. This trajectory, however, is still made up from free form curve segment, and unable to completely eliminate the effects on smoothness by line segment interpolation, which has a very adverse effect on the efficiency, tool life and machining accuracy. A new strategy to generate a continuous and smooth cavity cutting trajectories in high speed machining is introduced in this article. The new trajectory determines the necessity-nodes from outside (the boundary) to inside in the way of spiral cutting. It starts from the cavity center with spiral expanding, and each cutting loop adopts end connection between straight line and the tangent arc, meeting continuous first-order constraint satisfaction. The smooth trajectory reduces the amplitude and directing mutation of cutting force, thus effectively avoids the impact on the machining efficiency and machining accuracy by speeding down in the corner. The strategy also, by controlling the row space, ensures that there is no cutting residual. A cavity machining programming system based on this strategy is developed on Siemens UG-CAM module. The manufacturing of triangle cavities is studied as a case. It turns out that the new trajectory improves efficiency by 26.23% compared with the traditional one. It ensures a stable operation of the cutting tool in machining, therefore effectively extends the tool life. The main advantages are that the new strategy adopts the geometrical drawing strategy and the trajectories are all made up from the straight lines and the tangent arcs. The trajectory can greatly reduce NC code. It thoroughly removes the effort to mind the smooth, continuity and even cutting load of the tool-path.