The CNC machining machine feed drive has high requirements on position accuracy, fast response performance and speed regulation range. There are three main types of motors for CNC machining machines that implement feed drives: stepper motors, DC servo motors, and AC servo motors. At present, stepping motors are only used for economical CNC machine tools. DC servo motors are widely used in China. AC servo motors are gradually replacing DC servo motors as ideal transmission components. When the feed system of a CNC machine tool uses different transmission components, its transmission structure is different. There are three main forms of connection between the motor and the lead screw, as shown in Figure 6-9.
1, gear transmission
The connection form of the motor and the lead screw, the CNC machining machine generally adopts the gear transmission pair in the feed transmission device to achieve a certain speed reduction ratio requirement. Since the gear can not reach the ideal tooth surface requirement in the manufacture, there is always a certain error. A pair of meshing gears must have a certain flank clearance to work normally, but the flank clearance will cause the reverse drive clearance to the closed loop system. Said that the flank clearance will affect the stability of the system. Therefore, the gear transmission pair often uses a backlash mechanism to minimize the flank clearance.
2, synchronous belt drive form
The structure of this type of connection is relatively simple. Synchronous belt drive combines the advantages of belt drive and chain drive to avoid vibration and noise caused by gear transmission, but it can only be used in applications with low torque characteristics. The center distance requirement during installation is strict, and the manufacturing process of belt and pulley complex.
3, coupling transmission form
Usually, the motor shaft and the lead screw are connected by a taper ring without key connection or a high-precision cross coupling, so that the feed transmission system has high transmission precision and transmission rigidity, and the transmission structure is greatly simplified. This type of coupling is commonly used in machining centers and feed drives for high precision CNC machine tools.
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