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2025-11-24 03:29:38PRS Bearings
Crossed roller bearings are widely used in high-precision machinery, robotics, industrial automation, and CNC equipment due to their ability to support high radial, axial, and moment loads in a compact footprint. Despite their robust design, the performance and lifespan of these bearings heavily depend on preload—the initial axial force applied during installation.
Understanding preload and its effects is critical for engineers, machine operators, and maintenance teams who rely on accuracy, reliability, and smooth motion in demanding industrial applications. In this article, we dive deep into the concept of preload, its benefits, risks of incorrect application, and practical tips for achieving optimal bearing performance.
Preload refers to the intentional application of an axial load to a bearing assembly to eliminate internal clearance between rollers and raceways. This controlled pressure ensures that the bearing operates with minimal play, resulting in improved rigidity, precision, and smooth rotational motion.
In high-precision applications like CNC rotary tables, robotic arms, medical imaging devices, and semiconductor machinery, preload helps prevent backlash, reduces vibration, and maintains repeatability of motion—essential for consistent manufacturing quality.
Preload in crossed roller bearings can generally be classified into two types:
Light Preload
Light preload is applied to improve stiffness and reduce minor vibration without significantly increasing friction. It is suitable for applications requiring smooth motion and moderate precision.
Heavy PreloadHeavy preload eliminates almost all internal clearance, significantly enhancing rigidity and load capacity. This is ideal for high-precision machining,
rotary tables under heavy loads, and robotics with tight positional accuracy requirements.
Selecting the appropriate preload type is critical and should be based on the specific load, rotational speed, and precision requirements of the application.
Applying the correct preload offers multiple advantages:
Enhanced Rigidity
Preload strengthens the bearing assembly, allowing it to resist deformation under heavy or fluctuating loads. This ensures smooth operation even in demanding industrial environments.
Improved Rotational Accuracy
By removing internal clearance, preload enhances repeatability and precision in rotational motion. This is particularly important for CNC machining centers, robotic joints, and precision positioning systems.
Reduced Noise and Vibration
Bearings with optimal preload operate quietly and smoothly, improving overall machinery performance and reducing wear on associated components.
Extended Bearing Life
Correct preload distributes load evenly across the rollers, reducing localized stress and wear. This prolongs bearing service life and reduces maintenance costs.
Minimized Backlash
Backlash, or unwanted play in the bearing, can lead to positioning errors. Proper preload effectively eliminates backlash, ensuring higher machining and assembly accuracy.
While proper preload is beneficial, improper application can have severe consequences:
Excessive Preload
Over-tightening the bearing increases friction, generates excessive heat, accelerates wear, and can lead to premature failure. Over-preloaded bearings may also reduce rotational efficiency and require more energy to operate.
Insufficient Preload
Too little preload leaves unwanted internal clearance, causing vibration, reduced stiffness, and positional errors. In high-precision machinery, this can lead to backlash, lower accuracy, and inconsistent output quality.
Understanding these risks is crucial for maintenance and installation teams to ensure reliable and consistent operation.
To achieve optimal performance and longevity, consider the following best practices:
Follow Manufacturer Guidelines
Each bearing has specific preload recommendations based on size, series, and application. Adhering to these values ensures proper functionality.
Use Torque-Controlled Installation Tools
Consistent and precise preload is best achieved with torque-controlled wrenches or specialized preload measurement tools.
Regular Inspection and Maintenance
Bearings should be periodically inspected to ensure preload stability, lubrication condition, and absence of abnormal wear.
Consider Application Conditions
Factors like operating temperature, rotational speed, and load cycles influence the optimal preload. Adjust preload accordingly for high-temperature or high-speed operations.
Record and Monitor Preload Changes
Tracking preload over time allows early detection of wear, loosening, or misalignment, enabling proactive maintenance.
Robotics: Preloaded crossed roller bearings ensure precise arm movement, enabling accurate pick-and-place operations in automated assembly lines.
CNC Rotary Tables: Eliminating backlash maintains machining tolerances for high-precision components.
Medical Imaging Equipment: Smooth, precise rotation is essential for accurate imaging and patient safety.
Aerospace Components: Bearings under correct preload provide reliability in high-stress conditions.
Preload is not merely a technical step in bearing installation—it is a decisive factor influencing performance, precision, and service life of crossed roller bearings. Correct preload ensures smooth motion, high rigidity, minimized backlash, and extended bearing lifespan.
For engineers and maintenance teams, mastering preload application is key to maximizing equipment efficiency, reducing downtime, and ensuring consistent high-precision performance in industrial and robotic applications.
By understanding and implementing proper preload practices, businesses can achieve long-term operational reliability and a competitive advantage in precision machinery and automation sectors.
