| Virtual CNC cutting is a mapping of the real process in a virtual environment. The aim of it is to develop a visible machining environment to simulate and evaluate the influence of various machining process to machining result.Nowadays, CNC machine tools are used widely in manufacturing. In order to avoid the situation that NC equipments are damaged because of machining tool route errors, improve NC machining efficiency, shorten production cycles, reduce development costs, reduce the reject rate, the simulation of CNC processes is needed; CNC codes are checked on the computer in virtual cutting. On the other hand, it can also improve greatly the effect of teaching and training of CNC machine tools.The key technology of CNC turning simulation in 3D is discussed in this paper. Virtual CNC turning system is developed on the platform of Windows2000/XP OS, VC++6.0 and OpenGL.This project is accomplished as follows:1. Sum up the methods of solving 3D geometry molding problem and put forward a blend molding mode on the study of 3D geometry molding. Divide the geometry model into static model and dynamic model. An entity input interface is developed for the static model. System platform can mold a static 3D geometry model quickly by this interface.2. A virtual module library is created by the use of OpenGL display list technology. The 3D scene of Virtual CNC turning system is built by virtual assembly technology using the virtual module library, which is referenced on the CYNC-400 numerical control machine in Engineering Training Center of SooChow University. Motion control model of virtual machine tool is built by numerical control interpolation technology and 3D simulation of turning is implemented by computer cartoon technology. The dynamic model of virtual workpiece is built by discrete method.3. CNC code structure is analyzed and all kinds of errors in programming can be checked by using lexical analysis, syntax analysis and semantic analysis.4. The graphics check and information report of collision and interference is implemented. User can not only see the graphics display of collision and interference, but also know the coordinate of tool position when collision or interference happens. It offers convenience for user to consummate his NC code.5. Virtual control panel does exactly the same as the actual machine interface, including CRT display and MDI keyboard operation panel. By pressing the buttons, it can realize the corresponding operation functions, such as showing various parameters of the machine, editing or altering the procedures which are stored in the controller and also can activate the spindle clockwise or counterclockwise rotation and adjust its speed through the buttons.6. The help system module is designed for users to easily get system helps.Researches mentioned above have been fully integrated into CNC turning system SINUMERIK 802D. With its successful simulation, a good user interface and button control functions on virtual control keyboard, this system will bring great convenience to CNC teaching.
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