Study On Modeling And Machining Simulation Of Virtual NC Machine Tool System

NC(numerical control) machining tools have high productive efficiency, machining quality and flexibility which make them popularize rapidly. How to guarantee the validity of NC codes has become an outstanding problem in the NC machining process. With the development of computer graphics and visualization technology, it will be an efficient and economical way to display the cutter orbits or the machining processes on the screen to help manipulators check the validity of NC codes.In this paper, the basic conception of OOD(Object Oriented Design) is introduced to design virtual NC machine tool. According to their respective character in the machining process, all parts of the manufacturing system are classified into three classes: static objects, movable objects and workpieces. A method that utilizes solid modeling software to design the shapes of the static objects and the movable objects is proposed. The method simplifies the design of the virtual manufacturing environment through exporting STL(stereolithography) files from solid modeling software and converting them into OpenGL. A parametric feature modeling approach is adopted to create workpieces for simulating the material removal of workpieces in the machining process. The attributes combine with the animate member functions skillfully to compose the classes. Finally, the dynamic simulation of the virtual NC machine tool is implemented by manipulating the objects of manufacturing system.Collision detection is necessary to virtual NC lathe system. An efficient and exact collision detection algorithm is important to improve reality and to enhance immersion of virtual environment. Adopting reasonable spatial partitioning system and bounding volume hierarchy is anefficient way to speed up the collision detection process. In this paper, an octree algorithm based on spatial partitioning system is adopted and improved. The experiments illustrate that the algorithm accelerates the velocity of collision detection and ensures the real-time requirement of collision detection in virtual dynamic machining environment.The mechanism and rules of chip generating, curling and breaking, which provide warranty of chip modeling in the real-time machining simulation, are discussed. A parametric modeling method that uses spatial spiral curves to present the contour of chips and discretize the surface of the chips using triangle meshes is proposed to create chips. The method can simulate chip generating, curling and breaking through controlling the display lists.Finally, a demo system based on the algorithms is developed by using Borland C++ Builder 6 and OpenGL. It has been illustrated by experiment result that the methods can improve the sense of reality and real-time of 3D virtual environment and simulated machining process.