Modeling And Applications Of Levels Of Detail (LOD) For Surface CNC Machining Process Simulation

With the increasing complexity of simulation model, machining process simulations have to face the increasing conflict between simulation in real-time and the computational and storage capacity of the computer. In order to deal with this problem, the research work and innovative achievements presented in this dissertation are as follows:A novel simulation model for surface CNC machining process simulation, named G-LOD, is proposed and established. Simulations based on G-LOD can be carried out at different levels of detail and areas on surface models corresponding to different simulation aims, and this will save unnecessary computational time and storage space of the computer. Simulations based on G-LOD can obtain the machined solid model and vector-based model of surface simultaneously, so it can be used to evaluate the machining errors of machining process and verify CNC program. Because G-LOD is constructed on the basis of discrete CC path, machining simulations based on G-LOD will accord with the real machining processes more properly. Some simulation examples of surface CNC machining are completed. As an application in physical simulations, the method of dynamic cutting-force simulation of CNC machining is explored. From the simulation results it is found that using models of different levels of detail the computational time of computer will be decreased largely.A new CC path optimization method is presented. The optimized CC path is generated on the basis of iso-parametric CC path by using adaptive grid generation method. The optimized CC path possesses the merits of iso-scallop CC path and less number of discrete path than iso- scallop CC path, and so that it is a kind of optimal CC path. In the optimization process, the simulation model and method presented in this dissertation can be adopted to adjust grid factors and verify optimization results. The examples of real surface machining based on optimized CC path and iso-parametric CC path respectively have been completed. From the measurement results, it can be observed that the machining errors obtained by the optimized CC path are smaller than that obtained by iso-parametric CC path. The least-axis CNC grinding method for formed bits of mill roller is developed, and a 2.5 CNC grinding method is presented.Integrating the research fruits of this dissertation a prototype system of virtual grinding of formed bit of mill roller is developed. The system can fit the cutting edge profiles based on the given formed points, generate discrete CC path, optimize the generated CC path, produce G-LOD model of the bit, use the least-axis CNC machining method to simulate grinding the formed bit, and verify the obtained cutting edge profiles and clearances in the simulation.