Application
Robotics
Industrial robots are defined by their ability to repeat complex movements with consistent accuracy, thousands of times per shift, without deviation. A six-axis welding robot maintaining a 0.1mm path tolerance across a full production run, a SCARA robot placing components at 120 cycles per minute, a collaborative robot adjusting its torque output in real time to work alongside a human operator – in every case, the mechanical precision of the robot is inseparable from the precision of its bearing components.
The bearing’s role in a robot is more demanding than in most rotating machinery. It is not enough to support a shaft and reduce friction. In a robot joint, the bearing must transmit motion with near-zero backlash, maintain stiffness under varying load directions as the arm changes position, and do so within the tightest possible envelope – because every gram of weight and every millimeter of cross-section in a robot joint compounds across the kinematic chain. A bearing that introduces even marginal play into one axis affects the positional accuracy of every axis downstream.
Industrial robots span a wide range of configurations – six-axis articulated arms, SCARA robots, delta robots, collaborative robots, and Cartesian gantry systems – each placing distinct demands on their bearing positions. Thin section bearings, crossed roller bearings, and angular contact ball bearings address the majority of these requirements, with compactness and rigidity often weighted above raw load capacity in the selection criteria.
Products
Thin Section Bearings
The defining bearing type for robot joint design. Thin section bearings maintain an extremely small cross-section relative to their bore diameter – the ring dimensions remain constant regardless of bearing size, allowing large-diameter bearings to be specified without the weight and space penalty that standard bearings would impose. In a multi-axis robot arm, this matters at every joint: a thinner bearing profile at each axis reduces the moment of inertia of the arm, lowers the torque demand on the drive motors, and increases the useful payload fraction of the robot’s rated capacity. Thin section bearings in four-point contact or angular contact configurations are widely used in robot shoulder, elbow, and wrist joints, where combined axial and radial loads must be managed within a compact rotating assembly.
Crossed Roller Bearings
Where maximum stiffness and moment load capacity are required in a single compact unit – robot wrist assemblies, rotary joints in end-of-arm tooling, precision rotary tables integrated into robotic cells – crossed roller bearings are the standard solution. Their geometry places cylindrical rollers at alternating 90-degree angles between inner and outer rings, distributing load in all directions simultaneously and achieving a rigidity that ball bearings of equivalent size cannot match. This makes them particularly well suited to the wrist position of an articulated robot, where the bearing must resist moment loads from the tool and workpiece while maintaining the angular positioning accuracy that determines TCP (tool center point) precision. Crossed roller bearings also appear in harmonic drive and RV reducer output flanges – the precision reduction stages that define the positional resolution of each robot axis.
Angular Contact Ball Bearings
In the higher-speed positions of a robot – motor shaft supports within the joint actuator, spindle bearings in robotic machining heads, and the input stages of precision gearboxes – angular contact ball bearings provide the combination of speed capability, combined load handling, and dimensional accuracy that the application requires. Arranged in matched pairs or sets with controlled preload, they suppress the shaft play that would otherwise introduce positioning error into the control loop. In collaborative robots, where the drive train must be both compact and back-drivable for safety compliance, angular contact bearings in precision grades allow the actuator to meet torque density and backdrivability requirements simultaneously.
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FAQs
What loads can deep groove ball bearings handle?
Deep groove ball bearings are primarily designed for radial loads, but they can also handle moderate axial (thrust) loads in both directions. They are not suitable for heavy axial loads or combined shock loads. In those cases, angular contact or tapered roller bearings are preferred.
How do I select the right bearing size for my application?
Selection should be based on bore diameter (shaft size), required load capacity (dynamic rating C and static rating C0), operating speed compared with the bearing limiting speed, available space (outer diameter and width), and required precision grade from P0 to P2. Always apply a safety factor and verify that the calculated L10 service life meets your requirements.
What is the difference between open, shielded (ZZ), and sealed (2RS) bearings?
Open: No built-in protection, requires external sealing, and is suitable for clean environments or oil bath lubrication.
ZZ metal shields: Protect against dust and debris with low friction, making them suitable for high-speed applications, but they are not waterproof.
2RS rubber seals: Provide strong protection against dust and moisture. They are pre-greased and ideal for contaminated environments, but generate slightly more friction.
How often should I lubricate or replace the grease?
For general industrial use, grease should be replenished or replaced every 3,000 to 10,000 operating hours depending on speed, temperature, and environmental conditions. Bearings running above 70 C or in contaminated environments require shorter intervals. Sealed 2RS bearings are pre-greased for life and do not require re-lubrication.
What are the common causes of premature bearing failure?
The most frequent causes include inadequate or improper lubrication, contamination by dirt, dust, or moisture, incorrect installation, misalignment, excessive force during fitting, overloading beyond the rated capacity, improper shaft or housing fits, and fatigue at the end of normal service life.
How is the rated service life (L10) of a bearing calculated?
The basic L10 life is calculated as L10 = (C / P)^3 x 10^6 revolutions, where C is the dynamic load rating in kN and P is the equivalent dynamic bearing load in kN. It represents the number of revolutions that 90% of identical bearings will complete without fatigue failure. In practice, ISO 281 modified life calculations also apply correction factors for lubrication, contamination, material, and reliability.