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Help CenterONA ORB 20025 Thin-Walled Crossed Roller Bearing P4/P2 High Rigidity for Precision Rotary Table & Robot
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ONA RB Series – Thin‑Wall Crossed Roller Bearings
Product Overview
The ONA RB Series is the basic type of crossed roller bearings, featuring a compact thin‑wall design with high rigidity and excellent rotational accuracy. The series includes the standard RB (open type) and RB‑UU (double end face seal) structural variations.
In crossed roller bearings, cylindrical rollers are arranged perpendicularly to each other on the rolling surfaces of 90° V‑shaped grooves via spacer retainers. This unique 90° orthogonal arrangement enables a single bearing to withstand loads in all directions – including radial loads, axial loads (from both directions), and overturning torque loads.
Structural Design
The RB series is designed with a divided outer ring and an integrated inner ring. The outer ring is split into two parts in the axial direction, while the inner ring is a single‑piece construction. The cylindrical rollers are arranged in two 90° V‑shaped raceways at a 1:1 ratio, with spacer retainers placed between adjacent rollers to prevent direct contact.
This separated structure serves two purposes:
Simplified assembly – After inserting the rollers and retainers into the raceway, the split outer ring is fixed into position, preventing the bearing from disassembling itself during transport and handling.
Adjustable clearance/preload – Because the outer ring is split, the bearing clearance can be precisely adjusted. Even when preload is applied, high‑precision rotational motion is achievable.
Key Performance Advantages
Excellent rotational accuracy (P5/P4/P2) – The orthogonal roller arrangement, combined with spacer retainers that prevent roller tilting and friction, ensures smooth, accurate rotation without roller locking or skewing.
High rigidity – 3–4 times conventional bearings – The crossed roller design provides substantially higher rigidity compared to traditional bearing arrangements. Rigidity is further increased by 3 to 4 times.
High load capacity – With rollers arranged perpendicularly on a 90° V‑shaped raceway, a single RB bearing simultaneously supports radial loads, axial loads (bidirectional), and overturning moment loads.
Space‑saving thin‑wall design – The inner and outer ring dimensions are minimized to the practical limit. The ultra‑thin structure approaches the smallest possible size while maintaining high rigidity, significantly reducing installation space.
High rotational speed capability – The optimized roller geometry and nylon retainers allow higher operating speeds with stable performance across the speed range.
Low friction and low starting torque – Nylon separators reduce rotational inertia and starting torque, making angular positioning control easier.
Reduced shaft length and processing costs – The compact design shortens required shaft length, lowering material and machining costs. Thermal expansion causes only limited changes to geometric dimensions.
Optimized preload for high rigidity – The series supports precise preload adjustment, ensuring high system rigidity and accurate roller guidance.
Carburized steel for durability – Premium carburized steel provides excellent impact resistance and superior surface wear resistance for long service life in demanding environments.
Simple yet effective and smooth operation – The overall design combines simplicity with effectiveness, resulting in smooth, reliable, and maintenance‑friendly operation.
Available Variations
Based on the standard RB platform, the series includes additional variations to meet specific application requirements:
| Variation | Key Feature | Best Suited For |
|---|---|---|
| RB (Standard Type) | Spacer retainers; low friction coefficient; highly stable rotational torque | General precision applications |
| RB‑UU | Double end face seals on both sides | Applications requiring contamination protection |
| RB‑H (High Load Type) | Higher load rating with same external dimensions | Applications needing increased rigidity and load capacity |
| RBV (Full Roller Type) | No spacers; full roller complement; all‑metal compatible | Low‑speed, high‑load rotating operations |
Applications
The RB series is widely used across various high‑precision industries where space is limited but rigidity and accuracy are critical:
Industrial robots – Joints, swiveling units, and rotating parts
Machine tools – Rotary worktables (4th/5th axes) for machining centers
Precision rotary tables – Indexing and positioning applications
Mechanical hands/manipulators – Rotating sections
Medical equipment – CT scanners, surgical robots, precision diagnostic devices
Measuring instruments – CMMs, optical inspection systems
IC manufacturing devices – Wafer handlers, steppers, inspection equipment
Aerospace equipment – Actuators and positioning mechanisms
Comparison with Other Crossed Roller Types
| Series | Structure | Key Features | Primary Application |
|---|---|---|---|
| RB (Basic) | Outer ring split; inner ring integrated | Basic type; thin‑wall; high rigidity; inner ring rotation | General high‑precision rotary applications |
| RA | Outer ring split; thinner than RB | Ultra‑compact; lightweight | Robots, machine tools where space is extremely limited |
| RE | Inner ring split; outer ring integrated | Outer ring rotation accuracy | Applications requiring outer ring rotation precision |
| RU | Both rings integrated | Highest rigidity; simplest handling | Heavy‑duty applications with combined loads |
Precision Grades
ONA RB series bearings are manufactured to precision classes P5, P4, and P2 (equivalent to ISO Class 5, 4, 2), meeting the highest machine tool and robotics accuracy standards.
Standard Model Naming Convention
RB series models are designated by bore diameter × cross‑section height. Examples:
Summary of Key Selling Points
P5/P4/P2 precision – Highest accuracy grades available
High rigidity – 3‑4 times conventional bearings
High load capacity – Radial, axial, and overturning loads in one bearing
Ultra‑thin wall design – Minimal installation space
Outer ring split construction – Easy installation, adjustable preload
Spacer retainers – No roller‑to‑roller contact, low friction torque
Nylon separators – Low inertia, low starting torque
Carburized steel – Impact and wear resistant
Wide size range – From RB0604 to RB70045
Customization available – Seals, lubrication holes, special dimensions
ONA RB Series – Thin‑Wall, High Rigidity, Precision Crossed Roller Bearings
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