Trouble phenomenon: A gantry machining center equipped with FANUC 15MA CNC system, after the start is completed and enters the operable state, as soon as the X axis moves, high frequency oscillation occurs, the motor screams, and the system does not have any alarm.
Analysis and processing process: After the fault occurs, observe the X-axis carriage and find that the actual carriage vibration displacement is very small; but touching the motor output shaft, you can feel the rotor vibrating at a very small amplitude and extremely high frequency: and vibration The noise comes from the X-axis servo motor.
Considering that vibration occurs both during motion and when it is stationary, it has nothing to do with the speed of the motion, so it is basically possible to exclude the possibility of hardware damage such as speed generators and position feedback encoders.
The possible reason for the analysis is caused by improper parameter setting and adjustment in CNC related to the servo drive: and because the vibration frequency of the machine tool is very high, the current loop with a small time constant is more likely to cause vibration.
Since the FANUC 15MA numerical control system uses digital servo, the servo parameter adjustment can be directly performed through the system. During maintenance, the servo adjustment parameter page is called up and compared with the parameter table provided in the machine tool random data. The parameters PRMl852, PRMl825 and the provided value are found. No match, see below:
Parameter number Normal value Actual setting value
1852 1000 3414
1825 2000 2770
After the above parameters are revised again, the vibration phenomenon disappears and the machine tool resumes normal operation.