Research On The Key Techniques Of Precision NC Grinding Of Thread Surface

The grinding precision of thread grinding machine plays a very important part in the machining accuracy and performance of ball screw which is the machining workpiece of CNC screw grinding machine. The development of numerical control thread grinding technology has fundamental position and support function in enhancing the machining accuracy of ball screw. At present most CNC grinding machines adopt the solution of CNC integration which increases the grinding precision, but it also lacks stability at the same time. Combining the structural features of numerical control thread grinding machine, this paper is based on the numerical control thread grinding technology and do research on the numerical control thread grinding technology by means of mathematical modeling, finite element analysis software and experimental research methods. The research which is based on the established models including thread grinding force model, three-dimensional heat transfer temperature model and, elastic deformation model includes six parts, special as follows:1. Based on the mechanism of thread grinding and using the theory of grinding geometry, this paper analyzes the relations between the equivalent diameter of thread grinding wheel and the grinding wheel and the relations between the diameter of the workpiece and the spiral angle. This study is on the single grinding wheel abrasive grain and it established the grinding force model of the whole area after establishing the single abrasive grinding force model. Besides that, according to the heat transfer theory and the moving heat transfer theory, this paper also established a three-dimensional heat transfer temperature model whose object of study is grinding contact area and solved the three-dimensional heat transfer temperature model with the application of Laplace transformation, Fourier transformation and the characteristics of Dirac function.2. Because the contact arc length in the grinding between grinding wheel and workpiece is one of the important parameters in the grinding process, it has important effects on the grinding temperature in grinding area, grinding force and the elastic and plastic deformation of workpiece during grinding. According to the characteristics of thread grinding contact path, this paper also put forward the new formula for calculating the thread grinding dynamic contact arc length and analyzes the influence of grinding parameters on the thread grinding dynamic contact arc. Apart from that, this paper also compares the different grinding contact arc length under machining different material workpieces.3. This paper also established the elastic deformation model of grinding force and the mathematical elastic deformation model of the self-weight of workpiece separately after analyzing the main factors that affect the elastic deformation and the grinding precision of workpieces most. Besides, we analyze the elastic deformation of the workpiece specific to the condition that conducting grinding process with bracket support or not and conduct the optimal calculation in both cases. In the end, we get the smallest grinding contact point of the elastic deformation and we put forward the carrier tracking system and adaptive control method based on the two conditions.4. Affected by the factors like temperature, grinding heat, the increase of coolant temperature and local lighting, the calefaction of machining workpiece is uneven during the process of abrasive machining, thus appearing different heat deformation states. We make use of moving heat transfer theory and compare two-dimensional and three-dimensional heat transfer temperature field of grinding to get the temperature distribution in the process of grinding workpiece in radial and vertical direction based on the three-dimensional heat transfer model of the grinding temperature. We also get the temperature field cloud picture in radial and axial with the use of ANSYS software to conduct finite element simulation analysis on the grinding temperature distribution of the workpiece. Besides, we also carry out thermal structure coupling analysis to know the thermal deformation laws of workpiece and put forward the corresponding improvement plan through analyzing the influence of room temperature and coolant temperature on grinding quality.5. The errors that affect the thread grinding machining accuracy mainly come from the influences of grinding force deformation error and thermal deformation error. If we establish an error compensation system focused on a single factor, we may ignore the influence on the machining accuracy of other factors, so we need to establish a multi-factor comprehensive error compensation system to minimize the impact of the errors. According to the impact of grinding force and grinding temperature on workpiece machining error, we establish the comprehensive error compensation system using fuzzy neural network theory. Different comprehensive error compensation methods are proposed for two grinding bracket structures with bracket or not. Besides, we conduct simulation respectively to three fine grinding processes of workpieces. After analyzing the results of experiments, we could get the conclusion that the machining accuracy of workpiece improves significantly.6. After analyzing the grinding force, grinding temperature distribution and thermal deformation, we design the corresponding experiment scheme based on the SWM1530 screw grinding machine. We measure the corresponding data information with the use of acceleration sensor, inductive micrometer and dynamic strain indicator. Apart from that, we also predict the comprehensive error and conduct offline compensation experiments with the use of fuzzy neural network algorithm. All the results we get verify the effectiveness of the compensation results.This research could provide theoretical support and technological supports for the design of CNC screw grinding machine and provide a feasible method for improving the quality of thread grinding. The elastic deformation error model and thermal error comprehensive compensation model we need in the research have reference value for the error compensation for other thin rod workpieces. To sum up, this research has important theoretical significance to promoting the manufacturing level of CNC thread grinding machine of our country.