Research Of Technology And Software Development On Global Collision Detection In 5-axis NC-machining

Free-form surfaces have been widely used in aerospace, automobile and shipbuilding industries. These free-form surfaces are usually machined through 5-axis NC machines. 5-Axis machining offers many advantages over traditional 3-axis machining, such as shorter machining times, better tool accessibility and improved surface quality. However, because of the two additional rotational axes, collisions are prone to occur in 5-axis machining. These collisions may make the workpieces broken. Sometimes they even make the machine broken.With the needs of forming molds for composite material which been machined through 5-axis NC machines in aviation field, this dissertation makes research on the key technologies of global collision detection in 5-axis NC-machining, such as real-time simulation of 5-axis NC machine, hierarchical express of complex parts, primary collision detection based on the separation axis theorem, and accurate collision detection based on distance comparing among discrete points method. The main achievements are as follows:1. With the trait of simulation in 5-axis NC-machining, a software framework of global collision detection in 5-axis NC-machining is developed by using the technologies of rapid display, multithread programming, etc.2. The hierarchical express of tool and workpiece is researched and implemented, using the theories of hierarchical oriented bounding box (OBB) and improved linear octree. With these algorithms, the hierarchical models of tool and workpiece are built rapidly and exactly.3. Based on the hierarchical express of tool and workpiece, overlapping test between OBBs and octants of the surfaces octree with the separation axis theorem is implemented. The nodes which collisions occur can be primarily detected by using this method.4. Accurate collision detection based on distance comparing among discrete points method is researched and implemented. Whether the collision occurs between tool and the surfaces of workpiece is decided by comparing the distance between the nodes which collisions occur in primary collision detection and the axis of tool.5. Based on the researches of this dissertation, a software framework of global collision detection in 5-axis NC-machining is developed. And global collision detection is implemented in the machining of forming molds for composite material in aviation field.