Linear bearings are the backbone of motion systems in automation, robotics, and industrial machinery. But in start-stop applications, they’re often prone to premature wear. Let’s break down why this happens—and more importantly, how to extend the life of your linear motion system.
Common Causes of Linear Bearing Wear in Start-Stop Applications
1. Insufficient Lubrication at Startup
In intermittent motion, lubricant tends to settle or migrate away from contact surfaces. As a result, bearings operate dry during startup, increasing friction and accelerated wear.
2. Shock Loads and High Acceleration
Abrupt starts and stops introduce dynamic forces and micro-impacts, especially in high-speed applications. These repeated stress cycles cause surface fatigue on both bearing balls and raceways.
3. Stick-Slip Effect
The transition from static to dynamic friction leads to jerky motion, a phenomenon known as stick-slip. This creates uneven loading and significantly shortens the lifespan of linear bearings.
4. Contamination or Debris Ingress
Frequent motion changes can allow dust, chips, or fine particles to enter if bearing seals are inadequate. These contaminants act like abrasive agents, accelerating bearing wear.
5. Shaft Misalignment or Poor Tolerances
Linear bearings require precise shaft alignment. Deviations in roundness, straightness, or tolerance can lead to localized stress, resulting in uneven wear or bearing failure.
6. Overloading
Start-stop cycles can create dynamic loads that exceed static ratings. Without accounting for this in design, bearings can be overstressed, leading to rapid degradation.
Solutions to Improve Linear Bearing Life in Start-Stop Conditions
Use Bearings with Preload or Self-Alignment Features
These reduce play and maintain consistent contact pressure, minimizing vibration and wear.
Choose Sealed Bearings with Integrated Lubrication
Pre-lubricated and sealed linear bearings retain oil or grease longer and protect against contamination during idle periods.
Apply the Right Lubricant
Use high-viscosity grease or dry-film lubricants tailored for intermittent motion to prevent startup wear.
Install Hardened, Precision Shafts
A precision shaft improves guidance quality and minimizes uneven loading—key to long-lasting bearing systems.
Optimize the Motion Profile
Avoid abrupt starts and stops. Implement ramped acceleration/deceleration to reduce mechanical shock and stress.
Shaft Tolerance: h6 vs g6 – Which is Best for Linear Bearings?
When it comes to shaft fitting, your choice of tolerance matters—especially in precision linear motion systems.
h6 Tolerance – The Preferred Choice
Provides a tight sliding fit ideal for linear ball bearings
Minimizes play, vibration, and wear
Aligns with standard bearing designs for optimal performance
g6 Tolerance – More Clearance, Less Precision
Slightly looser than h6 (shaft is smaller)
Can cause increased vibration and noise
Sometimes used in dirty or high-temp environments, but not suitable for precision applications
Conclusion
Linear bearing wear in start-stop applications is often preventable. By understanding the causes—such as poor lubrication, misalignment, or incorrect shaft tolerances—and applying smart engineering solutions, you can extend bearing life and improve system reliability.
