| Based on the theory of virtual manufacturing, a new prototype system of machining accuracy prediction in virtual NC turning has been developed, which is able to imitate the real machining conditions, and predict the stability of machining process, the state of machining load and the machining accuracy of parts. This system can provide the technical supports, on the one hand, for optimizing the machining parameters, increasing production efficiency and improving the machining accuracy, on the other hand, for validating the process planning and NC program at a high level so that the NC machine tools can be utilized to its full function and performance, and the preparation time of production and the production cost can be significantly reduced.The original contributions of this dissertation in both theory and application of virtual manufacturing are:1.A concept of virtual measuring system is proposed for solving the machining accuracy prediction problem. It follows that the principle of building up the accuracy prediction system is proposed, and a method of constructing the virtual measuring system based on boundary modules and core modules is presented. In this virtual measuring system, the boundary modules are used for predicting the stability and efficiency of the machining system, and the core modules are used for estimating the accuracy parameters; together they implement the mapping from real measuring to virtual measuring.2.A 3-Instantaneous-Points method is proposed for shaping the virtual parts, where the machining system is simplified to the tool and the part interconnected by the tool coordinate system, the processing reference coordinate system and the spindle coordinate system. Synthesizing the errors given in the three coordinate systems in a proper way, the virtual parts containing errors are built up, which lays the foundation for machining accuracy prediction.3. A neural-network-based cutting-force prediction (NNBCFP) model is developed, which can improve the predicted accuracy from ?.5% to ?0.25%. In the meantime, this NNBCFP model gives the methods of predicting cutting power and evaluating the machining capability of the processing system.4. Modeling and solving the forced deformation of machining system is explored based on both the analytical method and the finite element method for inverse problem. An important finding is that with enough real measurement information, the original structuremodel can be replaced by the virtual structure solved from the inverse problem for the real-time evaluation of the virtual machining. This finding is verified by the experiment.5. A method of measuring and identifying the lathe motion error is proposed, where the coordinate system is related with processing system and machining state, the identification of geometrical errors and motion errors of the machine tool is accomplished by calibrating the error distribution in the corresponding coordinate axes. This method simplifies processing multiple error sources and lays the foundation for machining accuracy prediction.6. The individual coordinate system error and the whole machining system error are studied respectively for predicting the machining accuracy. The accuracy prediction model which takes the dimension accuracy, form accuracy, position accuracy and surface roughness into account, is developed, and the surface roughness prediction formula is derived based on the nose radius, the minor edge angle of the tool and the feed. This accuracy prediction model not only implements the machining accuracy prediction of the virtual parts, but also provides an applied guideline to reduce cost and optimize machining process.7. Chatter is used to predict the stability of machining state in this dissertation. A new method to predict chatter based on cutting force measurement is proposed and implemented by the non-regular coefficient method and the chatter threshold determination, where the chatter features are abstracted from the features of force and acceleration signals in both...
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