In the course of production practice, I observed that the glass bulb automatic press stamping cylinder experienced shaking during operation. The tremor varied in intensity but did not prevent the system from completing all required actions. The control system utilizes OILGEAR’s SC-VP series electro-hydraulic servo valve, which is a two-stage permanent magnet anti-debt servo valve. The working pressure is set at 9MPa. Upon analyzing the fault, it was determined that the issue stemmed from the servo valve's spool movement causing instability. This problem can generally be categorized into two main areas: electrical and mechanical.
Starting with the electrical side, possible causes included signal crosstalk, loose terminal connections, or hardware failures in the signal loop or servo amplifier. After thorough inspection, we ruled out AC signal interference, confirmed the terminals were securely fastened, and found no poor connections. Replacing the signal generation module and the servo amplifier hardware did not resolve the issue. Using an oscilloscope, the control signal was found to be normal, so we concluded that the electrical system was functioning properly.
Next, we moved on to the hydraulic side, checking for potential issues such as air in the hydraulic lines or cylinder, contaminated oil, severe cylinder leakage, or unstable main oil pressure. After eliminating these possibilities, the root cause was identified as the servo valve itself. Replacing the pilot section of the valve restored normal operation.
Upon disassembling the faulty valve, we discovered a significant amount of metal shavings in the gap between the torque motor’s magnet and armature. These shavings effectively reduced the air gap length (g) in the middle of the armature. According to the principles of hydraulic control systems, when |x/g| > 1/3 (where x is the displacement of the armature center), the armature becomes unstable. This indicated that the metal shavings had adhered to the permanent magnet, reducing the air gap and disrupting the torque motor’s static characteristics—this was the primary cause of the malfunction.
To address this issue and prevent similar problems in the future, several maintenance measures were implemented:
1. **Regular Oil Filter Replacement**: To prevent metal contamination from affecting the hydraulic oil, we established a schedule for replacing the oil filter and periodically draining and replacing the oil. This helps avoid dirt from entering the servo valve and extends its service life.
2. **Hydraulic Oil Replacement**: Hydraulic oil tends to degrade over time due to heat, wear, and metal particles generated by the pump, valves, and cylinders. Based on oil test results and the expected lifespan of the oil, we now replace it every 10 months to ensure reliable system performance and minimize unplanned downtime.
3. **Servo Valve Maintenance**: Since the root cause was contamination of the torque motor, regular cleaning and replacement of the torque motor and pilot valve became essential. Servo valves should be disassembled and reassembled in a clean environment, with proper precautions taken to disconnect the electrical signal and relieve hydraulic pressure before handling. All components should be cleaned using compatible solvents and dried thoroughly.
4. **Electrical Connection Checks**: Ensuring tight terminal connections and preventing signal loss is critical. Any poor contact or loose wiring could lead to performance issues, especially in sensitive systems like the servo valve. Regular checks and tightening of connections are necessary to maintain stability.
Overall, the servo valve is a high-precision electromechanical component that requires careful handling and regular maintenance. Understanding the importance of cleanliness, proper installation, and consistent monitoring is crucial to avoiding future failures and ensuring smooth operation.
Medicine Pulverizer,Pill Pulverizer,Pill Pulveriser,Pill Crusher Pulverizer
Jiangyin Xinda Medicine and Chemical Machinery Co.,Ltd , https://www.xinda-china.com