Use method and troubleshooting of NC machine tool coupling

CNC machine tool couplings are couplings specially used for CNC machine couplings. What can you know about the use of CNC machine tool couplings and troubleshooting? The following is the specific content of the CNC machine couplings brought by the technicians. I hope we can have some harvest!

The use method and precautions of CNC machine tool coupling

   Power-on debugging test bench host
Connect the other end of the three-phase four-wire cable (with a three-phase four-wire plug) to the power grid through the active maintenance switch, and close the active maintenance switch to send power to the test bench.
   Spindle rotation selection
According to the rotation direction of the mounted fuel injection pump, select the appropriate rotation direction on both sides of the test bench with the spindle rotation selection switch (L is left-handed, R is right-handed).
   Power-on investigation
Turn the main power switch on the back door to "1". At this moment, the experimental platform is powered on, and the digital tube on the exterior is on, indicating that the system has entered the operating state.
   Debugging of oil system
Press the fuel pump motor start button on the outside, and the light only glows, that is, the fuel pump motor starts to work. At this moment, pay attention to investigate whether the rotation direction of the fuel pump motor is the same as the direction marked on the fuel supply pump. Turn off the main power switch at the back of the test bench (set to the "O" position), and disconnect the three-phase four-wire cable that supplies power to the test bench from the grid (ie, disconnect the active maintenance switch).Then open the electric control door at the lower part of the experimental platform, find the three terminals R, S, and T connecting the three phase wires, connect the two arbitrary phase wires AC terminals between them (that is, change the phase), and connect them reliably to ensure No short-circuit connection.Close the electric control door, and then repeat the operations 1, 2, and 3.In this way, the rotation direction of the fuel pump motor is the same as the direction marked on the fuel supply pump.Find the fuel regulating valve in the center of the front panel of the test bench, turn it clockwise, the low pressure gauge will indicate low fuel pressure, and turn counterclockwise, the high pressure gauge will indicate high fuel pressure (the oil return joint should be blocked).
Preparatory work for commissioning test bench
   View coupling
If the coupling of the output main shaft has been removed, when installing the coupling, it is necessary to use a dial gauge to adjust it to ensure that it is coaxial with the output shaft. Note that the coaxiality is required to be 0.05mm.If the axis is different, it will cause oscillation.
   Check whether the protective cover is secured.
   Clamp the high-pressure oil pump.
Use the random clamping attachment to reliably clamp the high-pressure fuel injection pump to the working table of the test bench, and connect it with the main shaft coupling, and then connect the oil pipe between the test bench and the oil pump.If the fuel injection pump used is a distribution pump, you need to connect the 12V/24V power jack to the solenoid valve coil of the distribution pump, and use the toggle switch to select the appropriate voltage.
   Inject test oil
Open the double-sided side doors at the lower part of the experimental platform.Pay attention to the oil level display tube and do not let oil flow out of the tube.Pull out the fuel tank and pour 60 liters of test oil into the fuel tank.
   Connect the power cord
Ensure that the main power switch on the lower part of the experimental platform is in the "O" position, open the lower rear door, and introduce the unpowered three-phase four-wire cable with the appropriate capacity from the bottom hole of the experimental platform into the switchboard.If there is an outstanding ground wire user, please introduce the ground wire together.Please find the five unwired R, S, T, O, G or (ground) terminals at the bottom of the right terminal.Note that the O and G (or ground) terminals have been short-circuited when the product leaves the factory. If you have an outstanding ground wire, please remove the short wire and connect the introduced ground wire to the G (or ground) terminal reliably. The neutral wire of the phase four-wire can be connected to the O terminal; users who do not have an outstanding ground wire, do not remove the short wiring, please directly connect the imported three-phase four-wire neutral wire to the O terminal reliably.Connect the three phase wires of the three-phase four-wire to the R, S, and T terminals in sequence and reliably (one terminal is connected to a phase wire) to ensure that there is no short-circuit connection.Close the back door.

Removal of loose couplings of CNC machine tools

  The feed organization of CNC machine tools uses servo motors or stepping motors to connect with ball screws. Generally, direct couplings, toothed synchronous belts, or gears are used.In many occasions, due to structural constraints, especially after selecting a servo motor or a hybrid stepper motor, direct coupling has become a common connection method between the motor and the ball screw.
   Because the feed speed of CNC machine tools is relatively fast, such as fast forward and fast rewind, sometimes the speed is as high as 20m/min or more, and the forward and reverse rotation are frequent during the entire processing process.The momentary impact that the coupling receives is relatively large, which simply causes the coupling to loosen and change. As the use time increases, the loosening and changing conditions increase.In practice processing, the first manifestation is that the motion in all directions is normal, the encoder response is also normal, and the system has no alarm, but the motion value has not been able to match the command value, the processing error value is getting larger and larger, and even the processed part report is formed.
Waste.When this situation is present, it is recommended to check the coupling.
Couplings can be divided into rigid couplings and flexible couplings according to their structure, which can be treated separately according to their structure.
 1. Rigid coupling
   For rigid couplings, the coupling method of coupling sleeve and taper pin is the first choice, and most of the feed motor shafts are equipped with flat keys.This kind of connection, after a period of use, the taper pin becomes loose at the beginning, and the gap on the side of the keyway gradually increases, sometimes even causing the taper pin to fall, resulting in unstable parts processing dimensions.There are two ways to deal with it:
 (1) Use a special small-head taper pin with a thread, and lock it with a nut and an elastic washer to avoid loosening of the taper pin due to rapid conversion.This method can well deal with the problem of the looseness of the tapered pin, and at the same time it reduces the torque received by the flat key.Of course, this method has a nut on the small head of the tapered pin, which ensures that the coupling has a certain reversal space.
 (2) Choose two elastic pins, one large and one small, to replace the tapered pin. Although this method does not have the high accuracy of the tapered pin, it can deal with the loosening of the tapered pin. The elastic pin has certain elasticity and can be used. The split part of the flat key accepts the torque, and the structure is compact, and the installation is also very convenient.After being used in repair, it works very well.But pay attention to when installing, the large and small elastic pins are required to be installed at 180° to each other, otherwise it will affect the accuracy of parts processing.
 2. Flexible coupling
Flexible couplings are widely used couplings for CNC machine tools. They can compensate for the "dry and" phenomenon caused by errors in coaxiality and straightness.Under the condition that the structure permits, most of the servo feed systems of CNC machine tools use flexible coupling structure.However, it is difficult to know whether the taper sleeve is locked when the flexible coupling is installed. If the frictional force is insufficient after the taper sleeve is expanded, the relative slippage between the screw shaft head and the motor shaft head will change, resulting in the operation of the CNC machine tool In the process, the scale of the processed part shows a regular and gradual change (from small to large or large to small), and the value of each change is basically stable.If the rapid feed rate of the machine tool is adjusted, this amount of change will also change. At this moment, the CNC system does not alarm, because the motor rolling is normal, and the encoder's response is also normal.Once the machine tool presents this situation, the method of simply tightening the two-end screws does not necessarily have to be effective.The solution is to try to lock the elastic tapered sleeve of the coupling. If the tapered sleeve is too loose, the tapered sleeve can be slit axially, and the problem can be completely eliminated after tightening the screws at both ends.

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