1. Fault instance one
(1) Fault phenomenon When machining parts with XK5025 CNC vertical milling machine, the machining depth of the Z-axis of the parts often changes, resulting in parts failure.
(2) Failure analysis This phenomenon may be caused by the following reasons: 1 The reason of the part itself, such as the thickness of the part. After measurement, the thickness of the parts is the same, and this is excluded. 2 horns, workbench is not flat. After measurement, the horn and the workbench are normal, indicating that this phenomenon is not caused by the clamping. 3The milling machine tool is loose or not clamped, and the milling cutter moves up and down during the machining process. After inspection, the milling cutter has been clamped, not due to the depth change caused by the milling cutter. 4Z-axis motor line failure, replace the Z-axis motor line with the Y-axis motor line, the fault remains, indicating that the Z-axis motor line is normal. After repeated testing and analysis, it is found that the machining depth change of the parts is not fixed, and the above-mentioned reasons are excluded. Therefore, it may be caused by the spindle falling off, which is a problem with the spindle stepping motor. When the spindle stepping motor casing is disassembled, it is found that the bolt inside the spindle stepping motor is loose, so that the spindle cannot move normally when it moves, that is, sometimes it can be driven, sometimes it cannot be driven, and the depth of the part is changed during processing.
(3) Troubleshooting After tightening the bolts inside the spindle stepping motor, re-start the machining parts and troubleshoot.
2. Failure example two
(1) Symptom When using the table lift button to raise and lower the table, only the sound of the motor rotation can be heard, but the machine does not move up and down.
(2) Fault analysis Since the table lift is realized by the up and down buttons on the machine button box, it is controlled by the mechanical part, so this fault must be independent of the CNC system. First, consider whether the machine's up and down buttons are damaged. Pressing the up and down buttons, the sound of the motor is rotating, but the machine does not move, indicating that the up and down buttons are normal. Second, consider whether the mechanical drive of the machine tool is normal. Use the manual crank that comes with the machine to shake the table to see if you can move the table. After inserting the manual crank into the corresponding position in the direction of the lifting platform, the rocking handle is used for the ascending and descending movements, and it is found that both the ascending and descending are normal.
Based on the above, consider a problem with the motor that may control the rise and fall of the machine. When the motor casing was opened, it was found that the drive belt of the motor drive was broken and the fault location was finally determined.
(3) Troubleshooting A new belt can be replaced. But the original drive belt was broken, it was easy to take down, and the new drive belt was difficult to install. The specific steps for installing the new drive belt are as follows: one end of the drive belt is attached, and the other end is pressed with a screwdriver, but it can only be pressed up a little. When the push-up or down button is pressed, the drive belt will fall down and it will not succeed repeatedly. The method does not work.
We thought of disassembling the machine table to replace the belt, but considering this method, the workload was huge, and the accuracy of the machine was difficult to adjust after recovery, and finally gave up.
There is also a method of hot watering the belt, but after considering the perm, it may affect the life of the belt, and this method is also rejected. Finally, use a manual crank to solve this problem. We first put one end of the drive belt, the other end is pressed with a screwdriver, one person presses the drive belt with a screwdriver, and the other person slowly shakes up with a manual crank. In this way, the entire drive belt is finally mounted to the two pulleys.
After installation, restart the machine, the problem is solved, the belt drive is normal, and the machine can perform normal ascending or descending movement.
3. Failure example three
(1) Fault phenomenon When manually operating the XK5025 CNC milling machine, press the X-axis direction table button on the CNC system panel. The LCD display shows normal changes, but the actual X-axis coordinate axis does not move, and the system has no alarm display.
(2) Fault analysis Because the system does not alarm when the fault occurs and the display shows normal, the button is good. Replace the original X-axis encoder with a normal Y-axis encoder and find that the fault remains, indicating that the X-axis encoder is not damaged.
Since the display is normal, but the axis does not move, check whether the drive stepper motor of the machine is rotating to determine whether the fault is in the mechanical drive system or in the electrical control system. If the machine motor rotates normally, it can be determined that the fault is caused by a bad mechanical transmission system; if the machine's drive stepper motor does not rotate, the cause of the fault may be caused by a connection between the drive and the CNC or a drive failure.
After inspection, the machine's X-axis motor rotates normally, so it can be determined that the faulty part is in the mechanical transmission part. The X-direction movement is achieved by the stepper motor rotating the ball screw pair through the synchronous toothed belt, which in turn drives the table. The X-axis stepper motor housing was disassembled and it was found that the synchronous toothed belt inside the stepping motor was broken.
(3) Troubleshooting A new synchronous toothed belt of the same specification is replaced. The X-axis machine can move normally, the fault is removed, and the machine returns to normal.
4. Fault instance four
(1) Fault phenomenon There is obvious mechanical jitter in the Y-axis direction displacement of the XK5025 CNC milling machine table. The system does not alarm when the fault occurs.
(2) Failure analysis When the fault occurs, the system does not alarm, and observes the rate of the digital quantity of the Y-axis displacement pulse displayed by the CRT is uniform (obtained by observing the rate of change of the X-axis and Z-axis displacement pulse amount), so Eliminate system software parameters and hardware control circuit fault effects. Since the fault occurs in the Y-axis direction, the faulty part can be judged by the exchange method. The fault is not transferred by the AC servo control unit, so the fault location should be on the side of the Y-axis servo motor and the screw drive chain. In order to distinguish the motor fault, the flexible coupling between the motor and the ball screw can be disassembled and the motor can be checked separately. After inspection, there is no jitter when the motor is running, and it is obvious that the fault is in the mechanical transmission part.
There are four reasons for this phenomenon: the “wedge iron†of the 1Y axis “slider†is loose. There is dirt and small iron filings in the inverter inside the 2Y-axis ball screw nut. The 3Y-axis ball screw bearing is damaged. There is “axial sway†in the 4Y-axis ball screw or nut. Through the inspection of the machine tool, the "wedge iron" has no looseness, the Y-axis ball screw bearing is not damaged, and there is no dirt and small iron filings in the inverter inside the Y-axis ball screw nut, so the first three faults are eliminated. may. After inspection, it is finally confirmed that the looseness of the "back cap" of the ball screw nut is the root cause of the gap in the transmission.
(3) Troubleshooting After reinstalling the “back cap†and adjusting the machine clearance, the fault is eliminated.
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