Total pneumatic system failure? The machine should be maintained like this

The feed mechanism of the CNC machine tool is connected to the ball screw by a servo motor or stepper motor. Generally, it is directly connected by a coupling, connected by a toothed timing belt or connected by a gear. In many cases, due to structural limitations, especially after a servo motor or hybrid stepper motor is used, direct coupling becomes the most common connection method between the motor and the ball screw.

Because of the high feed speed of CNC machine tools, such as the speed of fast-forward and fast-reverse, sometimes up to more than 20m / min, the forward and reverse conversion is frequent during the entire processing process. The instantaneous impact that the coupling is subjected to is relatively large, which easily causes the coupling to loosen and twist. With the increase of the use time, the loosening and twisting of the coupling are intensified. In actual processing, the main performance is that the movement in all directions is normal, the encoder feedback is normal, and the system has no alarm, but the movement value can not always match the command value, the processing error value is getting larger and larger, and even the processed parts are scrapped. In this case, it is recommended to check the coupling.

Couplings can be divided into rigid couplings and flexible couplings according to their structure, which can be handled separately according to their structure.

1.Rigid coupling

At present, rigid couplings mainly adopt the coupling method of coupling sleeves and tapered pins, and most of the feed motor shafts are provided with flat keys. This kind of connection, after a period of use, the tapered pin begins to loosen, and the gap on the side of the key groove gradually increases, sometimes even causing the tapered pin to fall off, causing the machining dimensions of the part to be unstable. There are two solutions:

(1) A special conical pin with a small head and a thread is used, which is locked with a nut and an elastic washer to prevent the conical pin from loosening due to rapid conversion. This method can well solve the problem of loosening of the conical pin, and at the same time, reduces the torque suffered by the flat key. Of course, because this method has a nut on the small end of the conical pin, it is necessary to ensure that the coupling has a certain turning space.

(2) Use two large and one small elastic pins to replace the conical pin connection. Although this method is not as accurate as the conical pin connection method, it can solve the problem of loosening the conical pin. The elastic pin has a certain elasticity and can The torque of the disassembled flat key is compact, and the assembly is very convenient. After application in maintenance, the effect is very good. But pay attention when assembling, the large and small elastic pins are required to be assembled at 180 ° to each other, otherwise the accuracy of the part processing will be affected.

2.flexible coupling

Flexible coupling is a coupling widely used in CNC machine tools, which can compensate for the "interference" caused by coaxiality and perpendicularity errors. Under the condition that the structure is approved, the servo feed system of most CNC machine tools adopts a flexible coupling structure. However, it is difficult to grasp whether the taper sleeve is locked when the flexible coupling is assembled. If the friction force is insufficient after the taper sleeve is expanded, a relative slip and twist occurs between the screw shaft head and the motor shaft head, causing the CNC machine tool to operate. In the process, the size of the machined part changes regularly (from small to large or large to small), and the value of each change is basically constant. If the fast feed speed of the machine tool is adjusted, this amount of change will also change. At this time, the CNC system does not alarm. Because the motor rotation is normal, the encoder feedback is also normal. Once this happens to the machine tool, simply tightening the screws at both ends may not work. The solution is to lock the elastic tapered sleeve of the coupling. If the tapered sleeve is too loose, the tapered sleeve can be cut axially by a slit. After tightening two real screws, the failure can be completely eliminated.