| This paper analyzes the development status and research progress of CNC lathe and CNC turning center, found that it is an urgent issue to how to solve the demand of the main parameters: rotary diameter 400~630mm, the spindle speed 4000~8000r/min of the high-speed CNC lathes and turning centers, and the current situation of domestic electric spindle technology is one of the main causes for restricting its development. Summarizes the present situation of the development of domestic and foreign electric spindle technology, pointed out the inevitability of the research on the motorized spindle of CNC lathe and CNC turning center, which for the development of high-grade CNC machine tool, to further improve the research of the electric spindle technology is of great significance.Firstly, according to the performance index of electric spindle, the structure of the spindle is preliminarily designed, including the material selection, size determination of each component, preliminary design of cooling, lubricating and sealing systems, etc.Secondly, From the characteristics of electric spindle, to reduce the front end of the shaft maximum deformation, to increase the spindle static stiffness, to optimize design the the front overhang, rotor position and span of the spindle system, found that the front overhang have greatest influence on the maximum deformation of the front end of the main shaft, when the overhang is 70 mm, the right end face of front bearing to the left end face of the motor rotor distance is 56 mm and the bearing span is 230 mm. The minimum value of front-end maximum deformation is 5.6μm for the optimized design of spindle system.the dynamic analysis was did on the spindle system after optimization of the spindle system, established the finite element model, calculated the spindle-bearing system’s natural frequency, vibration mode and the speed limit, concluded that the maximum speed close to the first-order spindle limit speed, due to the vibration mode is translational motion, on the harmonic response analysis is found that when the exciting force is 1000 N, the front-end resonance shift is 5.6e-6mm,has a good dynamic stiffness, does not affect the machining precision, and the maximum speed is less than 30% of its second order limit speed, can satisfy the performance index of the spindle.Then, the overall structure of electric spindle is determined before the comparison of annular, single spiral and double spiral cooling method to draw the best cooling method for electric spindle, When determined the optimal cooling system, the boundary conditions at the same conditions, CFX fluid analysis of the three cooling methods, comparison of the shell temperature distribution at different cooling methods, determined the double spiral cooling mode is the best choice. After determining the spindle did the overall thermal state simulation, when the entrance of mass flow is 0.5Kg/s, the maximum speed is 8000 rpm, obtained the steady-state temperature field distribution of electric spindle, where the maximum temperature of the components is the front bearing, the temperature is 57℃. And applied the temperature as the load to the structure analysis, did heat structure coupling analysis, found the maximum deformation occurred in the back end of the spindle, the maximum displacement is 79.8μm.Finally, based on the Labview electric spindle speed intelligent control system is designed, through the transducer to control five sections speed of spindle and operation time of each segment speed, which reduced the testing time. And through the experimental measurement of the relationship between spindle speed and temperature, vibration, noise, the following conclusions are obtained:(1) Experimental measurement of 3 measuring point temperature of spindle under different rotating speeds, and comparison with the simulation results under rated speed, found that each measuring point temperature of the experimentally measured are basically consistent with the simulation results, the error is less than 2%, indicating that the thermal simulation method can successfully predict the temperature field distribution of electric spindle.(2) In the speed of 8000 rpm, by changing inlet mass flow of the cooling liquid, measured the temperature of the cooling liquid at the outlet, and determined the optimal flow rate of cooling liquid, discovered the best inlet mass flow of the double spiral cooling way is 0.55kg/s.(3) And measurement of the front end vibration value and noise value of the spindle under different speed, found that the noise value increased with increase of front end vibration value of the spindle, and the average noise of electric spindle was 28.5dBA, met the national standard, the vibration value is 1.8mm/s, which was excellent in rotating machinery vibration standards, met the job requirements. |
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