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

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There are several common faults that can occur in a servo system, and understanding these issues is crucial for effective troubleshooting and maintenance. Here’s a detailed breakdown of the most typical problems:

1. Overtravel: This happens when the feed motion exceeds either the software or hardware limits. The system will trigger an overtravel alarm, which is typically displayed on the CRT (Cathode Ray Tube) screen. To resolve this, you need to refer to the CNC system manual, reset the system, and clear the alarm.

2. Overload: Overload conditions usually arise from excessive load, frequent directional changes, or poor lubrication of the transmission chain. The CNC system may display warnings such as motor overload, overheating, or overcurrent. Additionally, the power cabinet’s feed drive unit might show indicators like LED lights or digital displays signaling overcurrent or overload conditions.

3. Feed Turbulence: This issue occurs when there is instability in the speed measurement signal—such as faulty sensors or feedback interference—or when the speed control signal is disrupted. Poor contact at terminals, like loose screws, can also cause turbulence. If it happens during direction changes, it may be due to backlash in the feed chain or excessively high servo gain.

4. Creeper Movement: This is often observed during acceleration or low-speed operation. It can be caused by inadequate lubrication, low servo gain, or excessive load. A misaligned coupling between the servo motor and the ball screw, especially if it's cracked or loose, can lead to jerky or uneven movement.

5. Machine Vibration: High-speed operation can result in machine vibration, sometimes accompanied by an overcurrent alarm. These issues are typically related to the speed loop. Any speed-related problem should be traced back to the speed regulator, checking both the input signal, feedback signal, and the regulator itself for faults.

6. Motor Not Turning: If the servo motor does not rotate, check whether the CNC system is sending a valid speed control signal and whether the enable signal (usually +24V DC) is active. You can use the CRT to monitor I/O states and analyze the machine’s ladder diagram or flowchart to ensure all starting conditions—like lubrication and cooling—are met. For motors with electromagnetic brakes, verify that the brake has been released. Other possible causes include drive unit failure or a faulty servo motor itself.