Gear transmission

    Gear transmission is a widely used mechanical transmission, and almost all gears of various machine tools have gear transmission. There are two purposes for using a gear transmission in a servo feed system of a numerically controlled machine tool. One is to change the output of high-speed torque servo motors (such as stepper motors, DC and AC servo motors, etc.) to the input of low-speed and high-torque actuators; the other is to make the ball screw and the table The moment of inertia is a proprietary smaller specific gravity in the system. In addition, the required motion accuracy is guaranteed for open loop systems.

    In order to minimize the influence of the flank clearance on the machining accuracy of the CNC machine, measures are often taken on the structure to reduce or eliminate the freewheel error of the gear pair. For example, the double-gear gear misalignment method is used, the eccentric sleeve is used to adjust the gear center distance, or the axial gasket adjustment method is used to eliminate the gear backlash.

    Compared with the synchronous toothed belt, the gear reduction gear is used in the CNC machine feed chain, which is more likely to generate low-frequency oscillations. Therefore, the damper is often equipped in the speed reduction mechanism to improve the dynamic performance.

    2. Synchronous toothed belt

    Synchronous toothed belt drive is a new type of belt drive. He uses the tooth shape of the toothed belt and the gear teeth of the pulley to sequentially transmit the motion and power, thus having the advantages of belt transmission, gear transmission and chain transmission, and no relative sliding, the average transmission is relatively accurate, and the transmission precision is high, and The toothed belt has high strength, small thickness and light weight, so it can be used for high speed transmission. The toothed belt does not need to be specially tensioned, so the load acting on the shaft and the bearing is small, and the transmission efficiency is also high, and it has been widely used in numerically controlled machine tools. The main parameters and specifications of the synchronous toothed belt are as follows:

    1) Pitch The pitch p is the distance between two adjacent teeth on the pitch line. Since the strength layer does not change in length during operation, the center line of the strength layer is defined as the pitch line (neutral layer) of the toothed belt, and the circumference L of the pitch line is taken as the nominal length of the toothed belt.

    2) Modulus The modulus is defined as m=p/π, which is a major basis for calculating the size of the toothed belt.

    3) Other parameters The other parameters and dimensions of the toothed belt are basically the same as those of the involute rack. The calculation formula for the tooth profile is different from that of the involute rack because the pitch of the toothed belt is on the strong layer, not in the middle of the tooth height.

The method of labeling the toothed belt is: modulus * width * number of teeth, that is, m * b * z.