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Case Analysis of Z-axis Overtravel and Side Overcurrent Faults of CNC Lathe

Failure analysis of CNC lathe servo system:
First, the CNC lathe servo system-z-axis overtravel fault case analysis

1. Failure phenomenon

A CNC lathe suddenly stopped working in automatic machining mode.

2. Fault detection, analysis and processing

  • a. On-site inspection of the CRT shows an alarm number of 52l, which is an overtravel alarm for the negative limit of the -Z axis. (Overtravel alarm, when the hardware overtravel is the limit travel switch is pressed, the overtravel alarm signal is sent to the CNC system to stop the CNC lathe to ensure man-machine safety; and software overtravel refers to the CNC system Set the corresponding parameters in it to prevent the tools on the worktable from exceeding the effective working area and to prevent the machine tool fixtures from being damaged by the tools).
  • b. According to the -z axis overtravel fault alarm, in manual JOG mode, use the handwheel (pulse generator) in conjunction with the feed override to move the table in the opposite direction of the alarm, that is, in the Z axis direction, remember not to be mistaken. (Note: If the manual cannot move in the opposite direction of the alarm, the power may be disconnected. Press the P button and CAN button on the CRT / MDI operation panel to turn on the power at the same time. Pay special attention to the RESET button and DELETE. Do not turn on the power when deleting the key. Wait until the workbench exits the machine tool overrun prohibition area and returns to the machine tool reference point before pressing the RESET key and the DELETE key.)
  • c. When dealing with this overtravel fault, only remove the CNC lathe worktable from the machine tool prohibited area, replace the damaged x18 limit switch, press the RESET key to release the alarm, return the worktable to the reference point of the CNC machine tool, and retry the normal operation.

3. Fault summary

This case is a hardware overtravel fault, such as a software overtravel fault. Just modify the corresponding parameters.Case analysis of overcurrent fault on the side of AC servo motor of CNC lathe

1. Failure phenomenon

A machine tool in a machining center will immediately alarm when it is turned on.

2. Fault detection and handling

  • a. Read the alarm diagnosis information on the Mitsubishi system CRT / MDI operation panel, the CRT display is (PR32, X). The alarm message is that there is an overcurrent problem on the AC servo motor side of the X-axis, which causes the system to enter the protection state.
  • b. In order to quickly distinguish whether the X-axis servo unit IPM crystal problem or the load X-axis AC servo motor is faulty, after the known good Y-axis AC servo motor and ACX-axis servo motor cable plug are exchanged, the fault is changed to the Y-axis servo The unit IPM crystal (referring to components such as the power amplifier module on the circuit board) and the load AC servo motor have an overcurrent fault; thus it is confirmed that it is a problem of the ACX axis servo motor and cable plug.
  • c. The AC servo motor is tested by the component replacement method, which proves that the AC servo motor is good.
  • d. Check the AC servo motor cable plug and socket and find that there is dirt and carbon deposit resistance oxidized between the terminals inside the socket, so confirm that this is the fault point.
  • e. Use the tip of a knife to scrape off the dirt and carbon deposits after discharge, and then brush and dry with industrial alcohol.
  • f. The alarm of the re-testing is eliminated, and the fault is smoothly eliminated.

3. Fault summary

The troubleshooting of the AC servo unit is also very critical. This type of failure has a high frequency and is universal. The cause of this case is due to the harsh environment of the machine tool in the machining center and the influence of the humidity of the cleaning machine nearby. Since then, the frequency of all types of failures has dropped significantly.

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