Robotic systems place very different demands on bearings compared with conventional industrial machinery.
A robot joint may require high rigidity and precise positioning, while a compact gripper may need a miniature bearing with extremely limited installation space. High-speed motors and encoders, meanwhile, often require low friction, low noise and consistent rotational accuracy.
For this reason, there is no single “robot bearing” suitable for every robotic application.
The correct bearing should be selected according to load direction, operating speed, required precision, rigidity, available space and working environment.
This guide explains the key factors engineers should consider when selecting bearings for robotics.
Why Bearing Selection Is Critical in Robotics
Bearings directly influence several important aspects of robotic performance:
- Positioning accuracy
- Rotational smoothness
- Joint rigidity
- Repeatability
- Noise and vibration
- Motor efficiency
- Service life
A bearing that is too loose may create positioning errors.
A bearing with excessive friction may increase motor torque requirements.
And a bearing that is too large may prevent engineers from achieving the compact structure required for modern robotic systems.
The goal is therefore not simply to choose the “highest precision bearing,” but to select the bearing design that best matches the actual operating conditions.
1. Identify the Main Load Direction
The first question is:
What type of load will the bearing carry?
Robotic mechanisms may generate:
- Radial loads
- Axial loads
- Combined radial and axial loads
- Moment loads
Different bearing designs handle these loads differently.
Radial Loads
Deep groove ball bearings are commonly used where radial loads dominate and compact size, low friction and moderate axial load capability are required.
They are frequently found in:
- Small robot motors
- Encoders
- Grippers
- Compact transmission systems
Combined Radial and Axial Loads
Angular contact ball bearings are suitable where both radial and axial forces must be supported.
Depending on the bearing arrangement, they can also provide increased rigidity and positioning accuracy.
Moment Loads and High Rigidity
Robot joints often generate overturning moments.
In these situations, crossed roller bearings or specially arranged angular contact bearings may be more suitable because they can provide higher rigidity in a compact space.
The exact bearing arrangement should always be calculated according to the actual load condition.
2. Consider Rotational Speed
Speed is another major factor.
A bearing used in a slowly rotating robotic arm joint has very different requirements from one used in a high-speed servo motor.
At higher speeds, engineers should pay particular attention to:
- Bearing internal design
- Lubrication
- Cage material
- Heat generation
- Rotational accuracy
- Friction torque
For high-speed motors, low-friction precision ball bearings are commonly preferred.
In some applications, hybrid ceramic bearings using silicon nitride balls can also provide advantages such as lower rolling mass, electrical insulation and improved high-speed performance.
However, ceramic bearings should be selected based on the actual operating requirements rather than treated as a universal upgrade.
3. Determine the Required Precision
Not every robotic application needs the same tolerance level.
A low-speed handling mechanism may work reliably with a standard precision bearing, while an encoder, servo motor or precision joint may require significantly tighter control of:
- Radial runout
- Axial runout
- Bore tolerance
- Outer diameter tolerance
- Internal clearance
- Rotational torque
The required precision should be determined from the complete mechanical system.
Using a higher precision grade than necessary can increase cost without improving real machine performance.
4. Evaluate Rigidity and Backlash
Rigidity is especially important in robot joints.
Even a small amount of bearing deflection can affect the position of the robot arm at the end effector.
Applications requiring high rigidity may benefit from:
- Crossed roller bearings
- Preloaded angular contact bearings
- Matched bearing arrangements
- Bearings with controlled internal clearance
Preload can improve rigidity and reduce play, but excessive preload increases friction and heat.
The correct balance between rigidity and rotational resistance is critical.
5. Check Available Installation Space
Robotic systems are becoming increasingly compact.
Many designers therefore need bearings with:
- Small outer diameters
- Thin cross-sections
- Low axial height
- Reduced weight
Miniature and thin-section bearings can help reduce the size of joints, grippers and actuators.
However, reducing bearing size also reduces available load capacity.
Engineers should therefore avoid selecting a bearing based only on physical size.
The bearing must still provide sufficient load rating and service life for the application.
Bearing Selection by Robotic Application
A useful way to choose bearings is to start from the location in the robot.
| Robotic Application | Main Requirement | Typical Bearing Options |
|---|---|---|
| Robot joint | High rigidity, low play, moment load | Crossed roller bearing, angular contact bearing |
| Servo motor | High speed, low friction, low noise | Precision deep groove ball bearing, hybrid ceramic bearing |
| Encoder | Low torque, high rotational accuracy | Miniature precision ball bearing |
| Gripper | Compact size, smooth movement | Miniature ball bearing, thin-section bearing |
| Robotic wheel / mobile robot | Radial load, shock resistance | Deep groove ball bearing, custom bearing |
| Compact actuator | Small footprint, controlled clearance | Miniature or custom precision bearing |
This table should only be used as a general starting point.
Final bearing selection should always be based on actual load, speed, dimensions and service conditions.
Miniature Bearings for Robot Grippers and Encoders
Miniature bearings are widely used in compact robotic mechanisms.
Typical advantages include:
- Small installation size
- Low rotational resistance
- High-speed capability
- Low mass
- Availability in shielded and sealed designs
They are commonly used in:
- Robot grippers
- Encoders
- Small motors
- Sensors
- Compact actuators
When selecting miniature bearings, engineers should pay close attention to tolerance consistency because very small dimensional differences can significantly affect fit and operating torque.
FR8ZZ Hex Bore Bearings for Robotics Applications
Some robotic systems require non-standard shaft interfaces.
One example is the FR8ZZ hex bore bearing, commonly used in robotics and educational robot systems where a hexagonal shaft must transmit torque without a conventional round-shaft connection.
Compared with a standard round-bore bearing, a hex bore design can simplify shaft connection in specific mechanical structures.
Key parameters that should be confirmed include:
- Hex bore size
- Outer diameter
- Bearing width
- Flange dimensions
- Shaft fit
- Required radial load
- Speed
For custom robotics projects, dimensional tolerance of the hex bore is particularly important.
A bore that is too tight may prevent assembly, while excessive clearance may create play and reduce positioning accuracy.
Ceramic Bearings for High-Speed Robot Motors
Ceramic and hybrid ceramic bearings may be considered for certain high-speed robotic motors.
Silicon nitride ceramic balls have lower density than steel balls and are electrically insulating.
Depending on the motor design, this may help in applications where engineers are concerned about:
- High rotational speed
- Electrical current damage
- Reduced rolling mass
- Friction
- Temperature
However, ceramic material alone does not guarantee better performance.
The complete bearing design, lubrication, preload and operating conditions must also be considered.
Lubrication Matters
Lubrication has a major effect on bearing torque, temperature and life.
In robotics, lubrication selection may need to consider:
- Operating speed
- Ambient temperature
- Load
- Required service life
- Cleanliness
- Noise requirements
Too much grease can increase resistance and temperature, especially in small high-speed bearings.
Too little lubrication can increase wear.
For precision robotic systems, lubricant quantity can be just as important as lubricant type.
Common Bearing Selection Mistakes in Robotics
Several mistakes repeatedly cause problems in robotic applications.
Choosing Only by Dimensions
Two bearings with identical dimensions may have different internal designs, tolerances, clearances and load capacities.
Dimensions alone are not enough.
Ignoring Moment Loads
Robot joints often generate moment loads that may not be obvious when only radial and axial forces are considered.
Using Excessive Precision
Higher precision is not always better.
Precision grade should match system requirements.
Ignoring Bearing Fit
Incorrect shaft and housing fits may cause excessive clearance, deformation or internal preload.
Overlooking Lubrication
A technically correct bearing can still fail prematurely if lubrication is unsuitable.
What Information Should You Provide When Selecting a Robot Bearing?
To recommend a suitable bearing, provide as much of the following information as possible:
- Bearing dimensions
- Shaft diameter
- Housing diameter
- Radial load
- Axial load
- Moment load
- Rotational speed
- Required accuracy
- Operating temperature
- Lubrication requirements
- Expected service life
- Application position
- Required quantity
For non-standard designs, drawings or 3D models are especially useful.
Standard and Custom Robotics Bearing Solutions
RMO Bearings supplies precision Robotics Bearings and customized bearing solutions for robotic and automation applications, including:
- Miniature precision bearings
- Deep groove ball bearings
- Ceramic and hybrid ceramic bearings
- Hex bore bearings such as FR8ZZ
- Thin-section bearings
- Custom non-standard bearings
- Custom roller and wheel assemblies
- Crossed roller bearings
- Precision angular contact bearings
For applications where standard catalog bearings cannot meet dimensional or operating requirements, dimensions, materials, seals, lubrication and other parameters can be evaluated according to the project.
Need Help Selecting Bearings for Your Robotics Project?
Bearing selection should start from the actual operating conditions rather than only the bearing model.
For a technical evaluation, send us:
Drawing + dimensions + load + speed + application + required quantity
Our team can help compare available standard bearing options and evaluate whether a customized solution is necessary.