In recent years, with the increase in processing requirements, international high-performance, high-speed, high-precision CNC machine tools generally use electric spindle units, especially high-speed CNC machine tools for grinding, which represents the future development trend of high-speed spindle technology. However, the electric spindle unit generates a lot of heat during high-speed operation. If the heat dissipation problem is not resolved, a large amount of heat will cause the spindle to thermally deform, thereby affecting the surface quality and machining accuracy of the workpiece. There are two main heat sources inside the electric spindle unit (D spindle bearing; ⑵ built-in main motor. Therefore, it is particularly important to explore the heat dissipation method of the stator surface of the electric spindle unit. The traditional high-speed electric spindle unit usually adopts a circulating cooling structure. The cross-sectional shape of the cooling tank and the spatial arrangement of the pipes are mainly designed based on experience. However, the empirical design does not fully consider the influence of the cross-sectional shape of the cooling pipe and the thickness of the wall between the pipes on the heat dissipation. For safety, the groove wall between the spiral pipes is generally designed to be wider, so the total heat dissipation area is reduced, Weakened the cooling effect. Using the relevant theory of the thin-walled cylinder model, starting from the stress and strain of the tube wall due to the pressure in the cooling liquid, through quantitative analysis of the minimum range of wall thickness, the cross-sectional size and shape of the cooling pipe on the stator surface of the high-speed spindle unit are optimally designed to improve The surface convection heat transfer coefficient increases the heat transfer area, thereby achieving the purpose of enhancing heat transfer; in addition, it provides a theoretical basis for the layout of the cooling pipe on the stator surface of the electric spindle unit. 2 The geometric model of the stator surface cooling duct 2.1 Overview of the stator surface cooling method When the spindle unit is running at high speed, a large amount of heat will be generated. If these heats cannot be taken away in time and effectively, the temperature of the main shaft will rise, and thermal deformation will occur along the axial and radial directions, thus affecting the surface quality of the workpiece, especially in precision and ultra-precision machining. . In order to reduce the temperature rise of the stator surface, an aluminum sleeve with spiral grooves is generally installed on the stator surface or the groove is directly slotted on the stator surface, and then the room temperature cooling liquid is passed into the groove, and the cooling liquid is transferred by convection heat exchange Take away most of the heat generated by the stator, so as to reduce the temperature rise of the stator. 2.2 Geometric model of the cooling duct The spiral cooling duct on the stator surface of the high-speed spindle unit, as shown. The traditional design of the cross-sectional shape of the pipe is designed based on experience, and there is no quantitative analysis of the influence of the wall thickness S on the cooling effect of the stator surface. In fact, the thin thickness of the wall has a great influence on the heat dissipation of the stator. The wall is equivalent to the fin, and its thin thickness directly affects the stator surface Feng Ruijin, etc .: the optimized design surface of the stator cooling pipe of the high-speed grinding electric spindle unit based on MATLAB The total heat dissipation area, and the size of the heat dissipation area is proportional to the heat dissipation. If the wall is too thick, the total heat dissipation area is reduced, and the heat dissipation is significantly reduced; if it is too thin, the wall may be deformed due to the inability to withstand the internal pressure from the cooling fluid, causing a gap between the cooling jacket and the shell, the pipe The liquid cannot be effectively sealed, and part of the fluid passes over the wall and enters the adjacent pipe, which affects the velocity of the fluid in the pipe, reduces the fluid velocity, and ultimately affects the amount of convection heat transfer on the stator surface. (A) The geometric model of the cooling duct 0)) The cross-sectional shape of the cooling duct The geometric model of the cooling duct on the surface of the electric main shaft stator: a, 6-the height and width of the cross section of the cooling duct; the thickness of the P wall. 3 Mathematical model of the cross-section parameters of the stator surface cooling pipe The parameters of the cross-sectional shape and wall thickness of the cooling pipe a, have the following functions L, A, Cp as independent parameters, 1, R, hP, P are non- Independent parameters. Non-independent parameters are determined by independent parameters Q, P, R. and physical properties of the fluid. Next, let's discuss some calculation models of non-independent parameters. 3.1 The mathematical calculation model of the actual pressure P at the entrance of the cooling pipe It is known that the energy loss in the cooling pipe on the stator surface is only the loss along the way Hf, that is, the energy loss caused by the fluid overcoming the resistance along the way on the uniform flow section, the formula average flow rate (M / s); g-acceleration of gravity (m / s). In addition, the loss of mechanical energy along the way, that is, the energy loss, is related to the pressure loss. From the above analysis, it can be seen that the actual pressure P at the entrance of the pipe should be: P = P0 + AP⑶3.2 The mathematical calculation model of the pressure loss AP of the cooling pipe 3.2.1 Mathematical calculation model of loss along the path ⑴ Loss along the flow Hf of laminar flow! : The losses along the laminar flow have been deduced in detail, and the results are as follows: / = 64 / Re⑷ In order to study the quantitative relationship between them, Nicolas has done a lot. Table 1 Optimization results under different flow rates Parameter name Pipe section coolant flow Pipe wall thickness Q ((Llmin) degree 5mlmm Stator material calculation results 45 steel 6 Finite element analysis and comparison of stator surface cooling pipes 6.1 Basic conditions for simulation analysis (1) The rated power of the motor is 41.9kW and the rated power loss is 1.5kW; (2) The compressed air pressure of the oil-air lubrication system is 0.15MPa and the temperature is 20T; (3) The ambient temperature is 20t; ⑷ The material of the stator is steel The length is 382mm and the diameter is 199mm. 6.2 Simulation analysis results and comparison 6.2.1 Empirical design results The temperature distribution of the cooling pipe and stator surface after cooling based on experience is shown in Table 2. Table 2 The temperature of the cooling pipe designed according to experience after cooling The pipe section width of the pipe section width blmm pipe wall thickness 5 (mm coolant flow rate Q ((Llmin) maximum temperature T (Yi stator material 45 steel 6.2.2 optimized design results According to the above theoretical formula, Matlab software is used to optimize the calculation, and Nastran software is used for simulation analysis. The results are shown in Table 3. Table 3 The temperature of the cooling pipe after the chemical design and the cooling of the cooling pipe The temperature of the pipe section of the pipe wall The maximum flow of the cooling liquid of the stator The thickness of the stator material 5 (mm T (Yi 45 steel 6.2.3 Simulation result comparison By comparing the two design results , The optimized design shows that under the same coolant flow rate, the optimized design has an obvious cooling effect compared with the empirical design. It is known from heat transfer theory that this is because the slot wall between the adjacent cooling pipes on the stator surface of the electric spindle unit Equivalent to fins, the thin thickness of the fins has a significant effect on heat dissipation. In the case where the stator length and slot width are fixed, the thinner the fins (that is, the wall thickness), the larger the total area of ​​heat dissipation, which is Increasing the heat dissipation area of ​​the stator surface of the electric spindle unit, the stronger the convection heat exchange, therefore, the heat exchange effect is significant. Under the same coolant flow rate, the cooling effect of the square cross-sectional shape is better than the cooling effect of the rectangular cross-sectional shape Significantly, in addition, the calculation of the parameters of the square section shape is more in line with the actual working conditions, so the simulation results are more accurate. 7 Conclusions The study of the cooling effect of the stator surface of the electric spindle unit is of great significance for high-speed grinding. Using Matlab and Nastran software as the platform, the mathematical and physical models of the cooling pipes of the electronic surface are established, and the correct boundary conditions are selected to complete. The optimization design of the cooling pipeline is compared with the two design results of empirical design and optimized design. Table 2 and Table 3 have listed the temperature data obtained by the two designs of empirical design and optimized design. Therefore, through the simulation analysis of the two designs, the following conclusions can be drawn. In the case of the same flow rate, the thinner the cooling tank wall, the better. Therefore, when designing the cooling tank width, the wall thickness should be designed to increase heat transfer under the premise of conforming to the mechanical model and processing technology conditions. The area is the main, that is, the thinner the better, considering the processing technology, it is recommended to design the wall thickness of 1mm; under the same flow rate, the cross-sectional shape of the cooling groove should be designed as a square. Dining Room Furniture,Dining Chairs,Dining Table And Chairs,Modern Dining Chairs Foshan Poesy Furniture Co., LTD. , https://www.poesy-furniture.com