Preload and duplex installation technology can significantly improve bearing rigidity, running accuracy, and load capacity. By eliminating internal clearance, bearings can achieve higher positioning accuracy and lower vibration.
Why is Preload Necessary?
Increased Rigidity
Eliminates clearance, reduces axial and radial displacement
Running Accuracy
Reduces vibration and runout, improves rotational precision
Load Capacity
Uniform load distribution, extends bearing life
Reduced Noise
Smooth operation, lower noise levels
Spring Preload
A spring preload is generated with the aid of one or more spring elements that act with a predetermined axial force against the end face of the outer ring or the inner ring of the ball bearing. With inner ring rotation, the spring washer is pressed against the outer ring (sliding fit). With outer ring rotation, the spring washer is pressed against the inner ring (sliding fit). myonic manufactures high-precision spring washers made of stainless steel for every standard bearing in our catalog.
It is essential that the two end faces of the spring washers are very parallel to each other to ensure correct preload and avoid misalignment of the ball bearings.
Spring Preload vs Ground Preload
| Characteristic | Spring Preload | Ground Preload (Axial Offset) |
|---|---|---|
| Preload Force | Adjustable | Fixed |
| Temperature Adaptation | Excellent (self-compensating) | Moderate |
| Installation Complexity | Simple | Requires precision grinding |
| Cost | Moderate | Higher |
| Application | General precision applications | Ultra-high precision applications |
Preloading of Duplex Bearings
To set the preload for two or more ball bearings with greater accuracy, the rings must be manufactured as shown in the illustrations. The axial offset of the inner ring face to the outer ring face determines the desired preload. During installation, the axial offset is eliminated and the preload is thus generated.
myonic duplex bearings are clearly marked for the correct installation position.
X Configuration (Suffix .9f)
In the X arrangement (face to face), the distance between the outer ring raceways is smaller than the distance between the inner ring raceways.
Illustration: X Configuration (face to face installation) - before installation / after installation
X Configuration Characteristics
The difference in raceway spacing arises during installation due to the elimination of a defined axial offset of the end faces. The axial offset of the inner ring face to the outer ring face is created by grinding the faces of the outer rings on one side of the ball bearing.
With the X arrangement, the effective distance between the bearing centers is reduced. The lines of contact converge. The distance between the virtual pressure points (intersection of the contact angle lines with the symmetry axis) is smaller than the track distance.
- High Rigidity: Excellent performance under radial and both axial load directions
- Tilting Moment Resistance: Wide contact line distribution, can withstand significant moment loads
- Versatile Application: Suitable for spindles, precision machine tools, medical equipment, etc.
- Error Tolerant: More tolerant with regard to alignment of the bearing system during installation
O Configuration (Suffix .9d)
In the O arrangement (back to back), the distance between the outer ring raceways is greater than the distance between the inner ring raceways.
Illustration: O Configuration (back to back installation) - before installation / after installation
O Configuration Characteristics
The difference in raceway spacing arises during installation due to the elimination of a defined axial offset of the end faces. The axial offset of the inner ring face to the outer ring face is created by grinding the faces of the inner rings on one side of the ball bearing.
With the O arrangement, the effective distance between the bearing centers increases. The lines of contact diverge. The distance between the virtual pressure points (intersection of the contact angle lines with the symmetry axis) is greater than the track distance.
Best Application Scenarios: The O configuration is particularly suitable for applications that must withstand large tilting moments, such as:
- Robot joints
- Rotary tables and indexing discs
- Large telescope rotation mechanisms
- Measuring equipment requiring high stability
- High-speed applications
Tandem Configuration (Suffix .9t)
The ball bearings can also be arranged in tandem. The contact lines run parallel and the radial and axial forces acting from the outside are evenly distributed. This arrangement offers the advantage of a higher axial load capacity in one direction.
Illustration: Tandem Configuration - before installation / after installation
Tandem Configuration Characteristics
Normally another bearing or another tandem bearing group is installed at the other end of the shaft in order to absorb any axial forces acting in the opposite direction.
| Axial Load Capacity | Very High (unidirectional) |
| Radial Load Capacity | Moderate |
| Tilting Moment Resistance | Lower |
| Typical Applications | Ball screw drives, thrust applications |
Configuration Selection Guide
| Application Requirement | Recommended Configuration | Reason |
|---|---|---|
| High radial load + moderate axial load | X Configuration (.9f) | Balanced load distribution |
| High tilting moment | O Configuration (.9d) | Maximum moment rigidity |
| Unidirectional high axial load | Tandem (.9t) | Double axial load capacity |
| Spindle applications | X Configuration (.9f) | Best overall performance |
| Rotary table applications | O Configuration (.9d) | Strong anti-runout capability |