Study On Generation Of Tool Path Without Interference For Blend Surface Along The Longitudinal Direction

During the progress of designing and machining for free surface product, the surfaces in many mold parts, such as the mold to make car bodies and the mold to make aerospace vehicles, often consist of transition and intersection areas among various types of surfaces which are called blend surfaces. As the transitional surface has at least two intersection base surfaces which will form a sharp corner, blend surface plays an important role in smoothing the area. Therefore, the blend surface will beautify the products, enhance the stiffness of the parts and improve the performance of stamping dies. At present, only ball-cutter and forming cutter can be used to machine blend surface. The cutting of blend surface using ball-cutter results in poor surface quality and low efficiency, which will directly affect the smoothing of blend surface. And the cutting method using forming cutter is only suitable for the simple blend surface with constant radius, many forming cutters are needed when cutting the mixing blend surface with variable radius, which brings about much trouble in the processing. It is clear that the wider effective cutting radius can be attained for flat-end cutter by changing the tilt angle of tool, and the cutting method with flat-end cutter can increase the processing efficiency and improve the surface quality.For this reason, a method in which the tool path will be generated along longitudinal direction of the blend surface spine using flat-end cutter is proposed in this paper. Base on the cutter contacts between blend surface and flat-end cutter, and in accordance with the properties of the blend surface and flat-end cutter geometry, a tool with smaller tilt angle than usual is used to increase effective cutting radius while guaranteeing no interference in the whole processes. In this method, both interference-free cutter locations and cutter orientations are carefully checked for every cutter contact because the effective cutting radius turns into bigger when the angle between the cutter axis and the normal vector of surface decreased.First, the cutter's orientation is determined based on curvature matching principle. Next, the gouging between the cutter and blend surface is detected by the developed gouging detection algorithm based on the technique of grid points, and the collision between the cutter and blend surface is detected by the developed collision detection algorithm based on the technique of distance calculation. At the same time, the cutter's orientation will be changed according to the results of interference detection to correct the positional relationship between the cutting edge and the blend surface, to achieve the cutter locations and to generate the tool paths forthe whole blend surface without interference. Further, based on the traditional constant scallop-height tool path generation method, a new optimization model is built to smooth the tool paths, to gain the cutter locations meeting the optimization model and to generate smooth tool paths.At last, a five-axis computer simulation is performed to illustrate the efficacy of this developed tool path generation method. The results of computer simulation demonstrate that the proposed method can avoid interface effectively, and the scallop height obtained after machining is more evenly and less volatile. Compared with the traditional cutting method with ball-cutter, higher cutting efficiency and smoother surface can be attained by the proposed method in this paper, which is properly applied to the actual machining in the near future.