Proper lubrication is essential for achieving rated life and maintaining performance. This guide follows THK and HIWIN lubrication recommendations.
1. Why Lubrication Matters
Lubrication forms a protective oil film between rolling elements and raceways, reducing friction, preventing wear, and dissipating heat. Inadequate lubrication is a leading cause of premature failure—lubrication issues account for over 50% of field failures.
2. Grease Types
Industry-recommended greases for linear motion components:
- AFB-LF (THK): Standard, -15°C to +80°C — General purpose, most applications
- AFA (THK): Low viscosity, -45°C to +80°C — Low temperature, high speed
- AFC (THK): High viscosity, -15°C to +130°C — High temperature, heavy load
- AFF (THK): Standard, -15°C to +80°C — Cleanroom, low dust generation
- Lithium #2: Standard, -20°C to +120°C — General industrial use
Do not mix different greases: Even with the same thickener, different additives may react adversely, degrading performance.
3. Lubrication Intervals
Recommended relubrication intervals:
- Standard (clean, normal load): Every 100 km travel or 3-6 months — Whichever comes first
- Heavy load/high speed: Every 50 km travel or 1-3 months — Reduce interval by 50%
- Dusty/humid environment: Every 30 km travel or monthly — Inspect more frequently
- Cleanroom environment: As specified — Use low-outgassing grease
4. Lubrication Quantity
- 15mm rail/block: 0.5-1.0 cm³
- 20-25mm rail/block: 1.0-1.5 cm³
- 30-35mm rail/block: 1.5-2.0 cm³
- 45mm+ rail/block: 2.0-3.0 cm³
Caution: Over-greasing can increase sliding resistance due to stirring resistance. After greasing, run the carriage through several cycles to distribute grease evenly.
5. For Oil Lubrication
When using oil lubrication (ISO VG 32-68 recommended):
- Flow rate: 1-5 drops per minute per lubrication point
- Oil viscosity should be maintained between 46-52 mm²/s at 40°C
- Check oil level regularly; consumption varies with operating conditions
6. Special Considerations
- Vertical mounting: Reduce relubrication intervals by 30-50%
- Vacuum/cleanroom: Use special low-outgassing greases (THK AFF series)
- High temperature: Use synthetic grease with appropriate viscosity rating
- Water exposure: Use water-resistant grease (lithium complex)
Pro Tip:
Signs of lubrication problems: Increased operating temperature, unusual noise (metallic sound), dark/discolored grease, or visible rust. Address immediately.
Conclusion
Regular lubrication is the single most important maintenance activity for linear motion components. Establish a schedule based on your operating conditions and stick to it.