Common faults in the servo system - Solutions - Huaqiang Electronic Network

Brand AVX TPSE226M035R0125 Low impedance tantalum capacitor, AVX 22

Electronic scale crystal oscillator, 3.2*2.5mm 3225, 16M (16.000MHZ), 12PF, 10PPM, 20PPM, 30PPM

SMD aluminum electrolytic capacitor

Single chip microcomputer STM32L151CCU6

ESD electrostatic protection tube, 5V two-way, 0201

There are several common issues that can occur in a servo system, and understanding them is essential for effective troubleshooting and maintenance:

1. Overtravel: This occurs when the movement of the feed axis exceeds the software or hardware limits set by the system. An overtravel alarm will be triggered, and the specific message will be displayed on the CRT screen. To resolve this, the machine should be manually moved back to a safe position, and the alarm should be reset according to the CNC manual.

2. Overload: When the load on the feed axis becomes too high, or if there is excessive movement in both directions, or poor lubrication in the transmission chain, an overload condition may develop. The system usually displays messages like "Servo Motor Overload," "Overheating," or "Overcurrent." Additionally, the power cabinet's drive unit may show indicators or digital displays signaling overcurrent or overload conditions.

3. Feed Instability (Turbulence): This phenomenon typically happens during direction changes. Causes may include unstable speed signals due to faulty sensors or feedback interference, unstable control signals, or poor electrical contact at terminals. If turbulence occurs during switching between forward and reverse motion, it could also be due to backlash in the feed chain or an excessively high servo gain setting.

4. Crawling During Low-Speed Feed: This issue often appears during acceleration or low-speed operation. It is commonly caused by inadequate lubrication, low servo gain settings, or excessive load. Another possible cause is misalignment or damage in the coupling between the servo motor and the ball screw, which can lead to jerky or uneven motion.

5. Machine Vibration at High Speeds: At high speeds, vibrations may occur, sometimes triggering an overcurrent alarm. These vibrations are typically related to speed control problems. Therefore, the speed loop and the speed regulator should be checked. Any speed-related issues should be traced back to the speed regulator, examining the input signal, feedback signal, and the regulator itself for faults.

6. Servo Motor Not Rotating: In some cases, the servo motor may not turn even though the CNC system sends a command. Along with the speed control signal, there is also an enable signal, usually a DC +24V relay voltage. Common diagnostic steps include checking whether the CNC system outputs a speed control signal, verifying that the enable signal is active, and observing the I/O status via the CRT. Checking the ladder diagram or flow chart can help determine if all start-up conditions—such as lubrication and cooling—are met. For motors with electromagnetic brakes, it's important to ensure the brake has been released. Other potential causes include a faulty feed drive unit or a defective servo motor itself.