Servo Drive System
Overview
HWAMDA injection molding machines use servo-driven hydraulic pump systems (servo-hydraulic) or direct-drive servo motors (all-electric). The servo system consists of:
- Servo drive (inverter / amplifier)
- Servo motor (PMSM — permanent magnet synchronous motor)
- Encoder (absolute or incremental)
- Brake resistor / regenerative unit
- Cooling system (fan or liquid-cooled)
Regular Checks
| Item | Frequency | Criteria |
|---|---|---|
| Drive cooling fan operation | Weekly | Fan spins freely at startup and during operation |
| Drive heatsink temperature | Weekly | < 75°C at rated load |
| DC bus voltage | Monthly | Within ±5% of nominal |
| Motor bearing noise | Monthly | No grinding, no high-frequency whine |
| Motor vibration | Monthly | < 2.5 mm/s RMS at rated speed |
| Encoder cable connector | Monthly | Seated fully, locking clip engaged |
| Brake resistor temperature | Monthly | No discoloration, no burned smell |
| Regenerative unit fan (if separate) | Monthly | Clean and operational |
Servo Drive Ambient Requirements
| Parameter | Requirement |
|---|---|
| Ambient temperature | 0–45°C |
| Humidity | 20–90% RH (non-condensing) |
| Altitude | ≤ 1000 m (derate above) |
| Air quality | No conductive dust, no corrosive gas |
| Cooling | Maintain airflow clearance per drive manual |
Common Alarms and Diagnostics
| Alarm | Likely Cause | Action |
|---|---|---|
| Overvoltage | Regenerative energy too high, brake resistor open | Check brake resistor continuity. Increase deceleration time. |
| Undervoltage | Weak mains supply, DC bus capacitor aged | Check mains voltage. Measure capacitor ESR. |
| Overcurrent | Motor short circuit, ground fault | Megger motor. Check motor cable insulation. |
| Overtemperature | Fan failure, heatsink clogged, overload | Clean heatsink. Replace fan. Check load profile. |
| Encoder fault | Encoder damaged, cable broken, connector loose | Check cable continuity. Replace encoder if needed. |
| Overspeed | Parameter error, encoder feedback loss | Verify speed loop tuning. Check encoder wiring. |
Preventative Maintenance
| Task | Interval |
|---|---|
| Clean drive heatsink (compressed air or vacuum) | Monthly |
| Replace cooling fan | Every 3 years (preventative) |
| Replace DC bus capacitors | Every 7 years or per OEM recommendation |
| Check brake resistor resistance | Yearly |
| Backup drive parameters to controller | After any parameter change |
| Update firmware (if OEM releases critical update) | As released |
⚠️
Servo drives contain high-voltage DC bus capacitors that retain dangerous voltage for up to 5 minutes after power-off. Verify DC bus voltage is below 50 VDC before touching any internal components. Use properly insulated tools.