The electric spindle spindle and the motor are integrated. Since they are integrated, there is no transmission mechanism in the middle.
Electric spindles are generally used by frequency converters. Through the asynchronous motor formula, we know that the speed of the motor is proportional to the voltage, that is to say, the lower the speed, the lower the voltage, and the torque of the motor is proportional to the square of the voltage. In other words, the lower the voltage, the greater the torque attenuation. If it is in a low-speed state, the torque of the motor using the inverter will be very small.
In order to obtain a relatively large torque at a low speed (usually when we are cutting large parts, the speed is relatively low, and because the parts are large, even if the cutting margin is not large, due to the large diameter, the torque is usually not small), generally In other words, gears are used to change speed, and the speed of the motor is not reduced to a very low level.
The electric spindle can be used, but it depends on the occasion. If the cutting occasion is above 2000 revolutions (the maximum voltage appears at 50HZ, the highest frequency is 200HZ electric spindle), or the milling and drilling spindle with a speed of 4000 revolutions or more (the maximum voltage is at In the case of 400HZ, the highest frequency is 400HZ), it is recommended to use an electric spindle, after all, there is no connection mechanism, and it is easy to use.
If it is not in these occasions, it is recommended to use variable frequency motor + gear box + frequency converter, with a wide torque output range, and two-stage gear shifting is fine.
With the rapid development of numerical control technology, "composite, high speed, intelligence, precision, and environmental protection" has become the main trend in the development of today's machine tool industry technology. Among them, high-speed Machining can effectively improve the machining efficiency of the machine tool and shorten the machining cycle of the workpiece. This requires the machine tool spindle and its related parts to adapt to the needs of high-speed machining. Spindle bearings for CNC machine tools are basically limited to four structural types: angular contact ball bearings, cylindrical roller bearings, bidirectional thrust angular contact ball bearings and tapered roller bearings.
With the high-speed development of CNC machine tool spindles, ceramic materials (mainly si3n4 engineering ceramics) have excellent properties such as low density, high elastic modulus, low thermal expansion coefficient, wear resistance, high temperature resistance, and corrosion resistance, which have become high-speed manufacturing Ideal material for precision bearings. Ceramic bearings are more and more widely used. In view of the difficult processing of ceramic materials, precision ceramic bearings are mostly hybrid ceramic ball bearings whose rolling elements are ceramic and the inner and outer rings are still made of chromium steel.
As a precise, efficient, and sensitive transmission element, the ball screw pair should not only use high-precision screws, nuts and balls, but also pay attention to selecting bearings with high axial rigidity, small friction torque and high running accuracy. In the past, ball screw supports commonly used bidirectional thrust angular contact ball bearings, tapered roller bearings, needle roller and thrust roller combined bearings, deep groove ball bearings and thrust ball bearings. The ball screw support is mostly single-row thrust angular contact ball bearings with a contact angle of 60°, and the accuracy is mainly p4 and above.
