Design Principles
The design of adjacent construction is critical for AXRY-NGS bearing performance. Deviations in the connection areas affect roller bearing accuracy and axis system performance.
Design Objectives
- Ensure geometric accuracy of bearing mating surfaces
- Provide sufficient rigid support
- Achieve effective thermal management
- Facilitate lubrication and maintenance
Recommended tolerances must not be exceeded to maintain bearing friction torque and operational properties.
Press Fits
When fits are excessively tight, radial bearing preload increases, causing the following issues:
Increases
- Surface pressure in raceway
- Bearing friction
- Wear rate
Decreases
- Maximum speed capability
- Bearing lifetime
Clearance Fits
Inadequate support of rotating bearing rings in clearance fits risks displacement of rotation axis relative to the worktable axis.
Warning
The clearance between fit bore and bearing can compound radial runout errors. Inner ring without support or insufficient support leads to uncertain operating conditions such as vibration, radial runout errors, and repeatability positioning errors.
The risk of radial runout errors or the loss of the rotation center of the rotary axis must be observed accurately over all operating conditions.
Intentional Clearance Fits
Intentional clearance fits to compensate for ring expansion are feasible, but require:
- Precise control and knowledge of temperature
- Careful vibration monitoring
- Close attention to radial runout errors
Minimum Wall Thickness Recommendations
To ensure sufficient rigidity and support, the worktable structure should meet the following minimum wall thickness requirements:
| Bearing Size | Min. Wall Thickness [mm] | Max. Passage [mm] |
|---|---|---|
| AXRY 120-NGS (-SBI) | 19 | 82 |
| AXRY 200-NGS (-SBI) | 22 | 156 |
| AXRY 260-NGS (-SBI) | 26 | 209 |
| AXRY 325-NGS (-SBI) | 27 | 271 |
| AXRY 395-NGS (-SBI) | 27 | 340 |
| AXRY 460-NGS (-SBI) | 30 | 400 |
| AXRY 580-NGS (-SBI) | 36 | 508 |
| AXRY 650-NGS (-SBI) | 45 | 560 |
Motor Integration Design
Heat from torque motors is one of the main challenges in high-speed axis design.
Recommendations for Reducing Heat Transfer
- Minimize contact area between stator and worktable housing to minimize heat flow
- If possible, do not connect stator cooling jacket to worktable housing
- Preferably connect rotor flange to worktable plate rather than bearing, to reduce heat flow through the bearing
- Maximize distance between motor and bearing
- Make bearing centering sufficiently rigid to achieve high system rigidity
Thermal Considerations
Asymmetrical housings require deformation analysis under thermal load. Temperature variations between shaft and housing can significantly affect bearing preload and performance.
Key Design Considerations
- Consider the entire system including cooling, thermal expansion, and component deformation
- Assembly rotation and friction torque measurement recommended during installation
- Asymmetric housings can deform during heating, thereby increasing bearing preload
- Eccentric clamping and high loads increase friction substantially
System Design Approach
Consider the entire system (cooling, thermal expansion, component deformation) rather than bearings in isolation. Only by considering the entire system can sufficient knowledge be gained to design appropriate cooling or heating/cooling systems.
Related Sections
- Shaft Fits - Shaft fit tolerance selection
- Housing Fits - Housing fit tolerance selection
- General Construction Notes - General design guidelines