Global Collision Detection And Tool Length Optimization

Using complex shapes and precise structures is one of the trends of modern advanced machinery manufacturing. 5-axis NC machining technology has obvious advantage in the manufacture of complex products. Compared with 3-axis NC machine, because of the two additional rotational axes, collisions are prone to occur in 5-axis machining. These collisions may break the workpiece. Sometimes they even break 5-axis NC machine.To meet the needs of forming molds for composite material machined through 5-axis NC machines in aviation field, this dissertation makes research on the key techniques of global collision detection in 5-axis NC-machining, such as real-time simulation of 5-axis NC machine, simulation model of 5-axis NC machine, effective usage of Separating Axis Theorem, collision detection base on multithread, method of calculate collision area, selection of the most suitable tool length, interactive optimization of spindle's angle. The main achievements are as follows:The simulation model for dynamic simulation and fast collision detection is created. The workpiece simulation model includes triangular mesh redundant vertexes filtering,triangular mesh simplification and space division by octree. NC machine simulation model includes division by polytope,parametric tool and chuck. The simulation model is the basement of dynamic simulation, collision detection and the most suitable tool length selection.A practical algorithm to judge the location between two objects is presented based on the simulation model. This algorithm is an effective usage of the Separating Axis Theorem. By this algorithm we can detect global collision effectively. At the same time a method to calculate the collision area is developed by this algorithm.The selection of tool length is directly related to the efficiency and quality of machining. This dissertation studies a tool length optimization method aiming at choosing the tool as short as possible in the prerequisite of guaranteeing no collision in the machining process. In addition, this dissertation provides a practical method for the revision and adjustments of NC code through interactive NC machine movement simulation.According to the features of 5-axis NC machine in aviation field, a software package of global collision detection in 5-axis NC-machining is developed by using UDP communication. Based on windows and OpenGL, the software system has a friendly interface and convenient operation which is compatible with the current popular CAD / CAM interface style. By using multithread programming skills, the system has high efficiency.