RA Series
Thin-Walled Crossed Roller Bearings
50–200mm Bore | 8–13mm Width | Lightweight Design | P5/P4/P2 Grade
The RA series is a thin-walled, lightweight crossed roller bearing specifically engineered for applications where every gram matters. The separable outer ring design enables easy installation and clearance adjustment. Trusted in collaborative robots, CNC direct-drive (DD) motors, CT scanners, and surgical robots — where compact design and precision are non-negotiable.
Lightweight Thin-Walled Crossed Roller Bearings for Compact Precision Machinery
Luoyang Songju RA series thin-walled crossed roller bearings deliver the high rigidity and multi-directional load capability of crossed roller bearings in the lightest, most compact package available. The separable outer ring (two-piece) design combined with a one-piece inner ring enables straightforward installation with adjustable clearance or preload.
With widths of just 8–13mm across the entire bore range (50–200mm), the RA series achieves dramatic weight reduction compared to standard crossed roller bearings — critical for collaborative robot arms where reduced joint mass directly improves payload-to-weight ratio, energy efficiency, and safety in human-robot collaboration scenarios.
Available in P5 (ABEC-5), P4 (ABEC-7), and P2 (ABEC-9) precision grades from GCr15 bearing steel. Standard type (open) and sealed type (suffix UU) configurations are available. The RAU sub-series offers the same dimensions with an integrated inner/outer ring structure for applications requiring non-separable ring handling.
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RA Series — Thin-Walled Crossed Roller Bearing Model Parameters
Complete standard model list for RA series thin-walled crossed roller bearings. Corresponding CRBS (IKO) model numbers provided for cross-reference. RAU series features integrated (non-separable) rings with same dimensions.
| Bearing Model | d (mm) | D (mm) | B (mm) | Cr (kN) | C0r (kN) | Mass (kg) |
|---|---|---|---|---|---|---|
| RA 5008 (CRBS 508) | 50 | 66 | 8 | 5.1 | 7.19 | 0.08 |
| RA 6008 (CRBS 608) | 60 | 76 | 8 | 5.68 | 8.68 | 0.09 |
| RA 7008 (CRBS 708) | 70 | 86 | 8 | 5.98 | 9.8 | 0.1 |
| RA 8008 (CRBS 808) | 80 | 96 | 8 | 6.37 | 11.3 | 0.11 |
| RA 9008 (CRBS 908) | 90 | 106 | 8 | 6.76 | 12.4 | 0.12 |
| RA 10008 (CRBS 1008) | 100 | 116 | 8 | 7.15 | 13.9 | 0.15 |
| RA 11008 (CRBS 1108) | 110 | 126 | 8 | 7.45 | 15.0 | 0.16 |
| RA 12008 (CRBS 1208) | 120 | 136 | 8 | 7.84 | 16.5 | 0.18 |
| RA 13008 (CRBS 1308) | 130 | 146 | 8 | 7.94 | 17.6 | 0.19 |
| RA 14008 (CRBS 1408) | 140 | 156 | 8 | 8.33 | 19.1 | 0.21 |
| RA 15008 (CRBS 1508) | 150 | 166 | 8 | 8.82 | 20.6 | 0.22 |
| RA 16013 (CRBS 16013) | 160 | 186 | 13 | 23.3 | 44.9 | 0.62 |
| RA 17013 (CRBS 17013) | 170 | 196 | 13 | 23.5 | 46.5 | 0.68 |
| RA 18013 (CRBS 18013) | 180 | 206 | 13 | 24.5 | 49.8 | 0.71 |
| RA 19013 (CRBS 19013) | 190 | 216 | 13 | 24.9 | 51.5 | 0.74 |
| RA 20013 (CRBS 20013) | 200 | 226 | 13 | 25.8 | 54.7 | 0.78 |
All models available in P5, P4, and P2 precision grades. IKO equivalent: CRBS series. RAU = integrated ring type (same dimensions). Suffix UU = double sealed. Suffix C1 = specified clearance. Custom lightweight materials and specialty coatings available for medical and aerospace applications.
Why Choose Luoyang Songju RA Thin-Walled Crossed Roller Bearings
Maximum rigidity in the lightest possible package — engineered for collaborative robotics and medical devices
Ultra-Lightweight Design
Weighing as little as 0.08 kg (RA 5008), the RA series achieves dramatic weight savings over standard crossed roller bearings. Every gram saved at the robot joint translates to higher payload capacity, faster cycle times, and reduced motor power requirements.
Thin-Walled Profile
Width of just 8mm for bore range 50–150mm and 13mm for bore range 160–200mm. The ultra-thin wall design minimizes the bearing's contribution to overall mechanism size — enabling compact, elegant machine designs.
Separable Outer Ring
The two-piece outer ring design allows easy installation and fine adjustment of internal clearance or preload. Achieve zero-clearance or preloaded operation for maximum positioning accuracy in precision motion systems.
Collaborative Robot Ready
RA series bearings are specified by leading cobot manufacturers worldwide. The combination of light weight, high rigidity, and smooth motion directly supports the safety, precision, and energy efficiency requirements of ISO/TS 15066 collaborative robot applications.
Premium GCr15 Steel
Rings precision-ground from vacuum-degassed GCr15 (100Cr6 / 52100) bearing steel. Consistent hardness (58–64 HRC) and controlled retained austenite ensure dimensional stability throughout the bearing's service life under varying load and temperature conditions.
RAU Integrated Alternative
The RAU sub-series offers identical dimensions with an integrated (non-separable) ring structure. Choose RA for adjustable clearance applications, RAU for simplified handling where pre-set clearance is acceptable. Both share the same mounting envelope.
Industries & Applications for RA Series Thin-Walled Crossed Roller Bearings
RA Series crossed roller bearings are trusted across a wide range of precision industries worldwide.
Collaborative Robots (Cobots)
RA series is the dominant crossed roller bearing in collaborative robot joints. Light weight improves payload-to-weight ratio and reduces collision energy for safer human-robot interaction. 8mm width series covers the most common cobot joint sizes (50–150mm bore).
Direct Drive (DD) Motors
Thin-walled design integrates seamlessly into DD motor housings for CNC rotary tables and precision indexing systems. High rigidity supports the heavy cutting loads typical of direct-drive machine tool applications.
CT Scanners & Medical Imaging
Smooth, silent rotation with minimal torque variation — essential for CT gantry rotation where image quality depends on precise, vibration-free motion. Sealed (UU) variants prevent grease migration in clinical environments.
Surgical Robots
The combination of compact size, light weight, and high precision makes RA series the preferred choice for surgical robot joints. P2 grade bearings deliver the sub-arcminute positioning accuracy required for minimally invasive procedures.
Need RA Series Thin-Walled Crossed Roller Bearings?
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