Research On Collision Detection Algorithm For Five-Axis NC Machining

Five-axis NC machining technology has been the most important facility in manufacturing industry. However, because of its two rotating axes, it is difficult to catch the space position of every part, which may cause processing accident. Therefore, collision detection among all the parts is important in NC machining simulation to avoid the processing accident.There are many studies about collision detection of virtual simulation in both China and abroad, and these achievement should be applied to simulation of NC machining. Because of the easy control of triangular facet, it is also adopted in NC machining simulation. But in order to be adapted in NC machining simulation, algorithm of collision detection used in virtual simulation should be improved according to characteristic of NC machining simulation.OBB is adopted and optimized for collision detection of convex part in NC machining simulation. Although, separation axis authenticity is widely used in the collision detection of OBB, because of its blindness, a large amount of calculation are required. So a new detecting method, which is transforming collision detection of three-dimensional bounding box to two-dimensional, has been proposed in this thesis to improve the calculating efficiency.For collision detection between machine shell concave and other part, inner bounding boxes is applied to avoid directly dividing concave to convex. Since the bounding boxes are so big that they often interfer at the beginning, resulting in large calculation, while inner bounding boxes can removes many cases of non-collision effectively, and then improves the efficiency.Triangle-triangle intersection is adopted directly in precise detection of NC machining simulation. After comparing every algorithm through adding a way similar to AABB in the beginning, an optimization of tropp algorithm is proposed. A preprocessing where the maximum and minimum data are stored is needed in every direction process when storing the chained list of triangle’s point, and then a preliminary detection can be completed by comparing these value. It makes up the low detection efficiency in tropp at the low rate of interference.Discrete collision detection may lead to the missing of some situations for the collision detection between cutter and workpiece, so a workpiece and swept volume of a cutter was utilized to perform the collision detection, so a continuous collision detection is achieved.The collision detection of five-axis NC machining simulation based on the collision detection of virtual simulation is completed in this thesis. Meanwhile these proposed algorithms of this article can also be used to other situation of virtual simulation.