Full complement cylindrical roller bearing without outer ring: High‑load solution for heavy‑industry applications
What is a full‑complement cylindrical roller bearing without an outer ring?
A full‑complement cylindrical roller bearing without an outer ring is a special rolling bearing designed to maximize radial load capacity while minimizing installation space. Unlike conventional cylindrical roller bearings that use cages to separate rolling elements, full‑complement bearings incorporate the maximum possible number of rollers, greatly enhancing load‑carrying capacity.
In this design, the outer ring is eliminated, and rollers roll directly on hardened, precision‑ground shaft or raceway surfaces. This structure delivers a compact bearing solution with outstanding rigidity and load capacity, making it suitable for heavy‑duty industrial equipment.
Common bearing series include:
SL18 series
SL19 series
NCF series
NNCF series
RN series
RSL series
Double‑row full‑complement bearings
Multi‑row full‑complement bearings
Widely used models include:
SL185008
SL182212
NCF2930V
RN2220
NNCF5008CV
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Bearing Structure and Design Features
A full‑complement cylindrical roller bearing without an outer ring generally consists of:
Inner ring
Cylindrical rollers
Rings or guide components
Lubrication grooves (optional)
Unlike standard caged bearings, there is no cage to separate the rollers. The additional rollers increase the contact area between rolling elements and raceways, markedly boosting radial load capacity.
Key Structural Advantages
Maximum Number of Rollers
More rollers translate to:
Higher static load rating
Higher dynamic load rating
Improved load distribution
Reduced contact stress
Compact Design
By removing the outer ring, designers can achieve:
Reduced assembly dimensions
Larger shaft diameter
Improved overall equipment rigidity
Direct Shaft Raceway Operation
Rollers roll directly on machine shafts or hardened housing raceways, reducing part counts and simplifying certain machine designs.
Differences Between Full‑Complement Bearings and Standard Cylindrical Roller Bearings
|Feature|Full‑Complement Bearing|Caged Bearing|
| ---- | ---- | ---- |
|Roller Quantity|Maximum|Limited|
|Radial Load Capacity|Very High|High|
|Speed Performance|Moderate|Higher|
|Rigidity|Excellent|Good|
|Shock Resistance|Excellent|Good|
|Installation Space|Compact|Larger|
|Bearing Service Life Under High‑Load Conditions|Longer|Shorter|
For high‑load applications, full‑complement cylindrical roller bearings are selected more frequently than standard NU, NJ, NUP, and N‑series cylindrical roller bearings.
Main Advantages of Full‑Complement Cylindrical Roller Bearings
Excellent Radial Load Capacity
The primary reason engineers select full‑complement bearings is their ability to sustain extremely high radial loads.
Major application industries include:
Mining
Steel production
Heavy‑duty gearboxes
Construction equipment
Wind power generation systems
Superb Rigidity
The increased number of rollers creates a highly rigid bearing structure that minimizes shaft deflection under heavy loads.
This characteristic is especially critical in:
Precision gear drives
Rolling mills
Crane systems
Industrial power transmission units
Enhanced Shock Load Resistance
Heavy‑duty industrial machinery is frequently exposed to:
Shock loads
Vibration
Fluctuating loads
Full‑complement bearings distribute these loads across more rollers, lowering localized stress concentrations.
Longer Service Life Under High‑Load Conditions
With proper lubrication and operation within design limits, they often achieve longer service life than caged cylindrical roller bearings in heavy‑duty environments.
Typical Application Fields
Industrial Gearboxes
One of the largest application areas for full‑complement cylindrical roller bearings is industrial gear reducers.
Applications:
Planetary gearboxes
Helical gear reducers
Extruder gearboxes
Wind turbine gearboxes
The high rigidity of the bearings improves gear meshing precision and power transmission efficiency.
Mining Equipment
Mining machinery operates in the harshest working environments.
Representative equipment:
Crushers
Conveyor systems
Stackers
Reclaimers
Ball mills
Bearings withstand:
Severe shock loads
Dust contamination
Continuous operation
Steel and Metallurgical Industry
Steel mills require bearings capable of enduring:
High temperatures
Heavy rolling forces
Severe shock loads
Application fields:
Rolling mills
Continuous casting equipment
Cooling bed systems
Shearing machines
Construction Machinery
Used for:
Excavators
Cranes
Pile drivers
Tunnel boring machines
The compact design offers particular benefits where installation space is limited.
Wind Energy Industry
Modern wind turbines increasingly adopt full‑complement cylindrical roller bearings in the following components:
Main gearboxes
Generator systems
Pitch control mechanisms
High load capacity extends maintenance intervals and enhances reliability.
Description of Full‑Complement Bearing Series
SL18 Series
SL18 bearings are among the most widely used full‑complement cylindrical roller bearings.
Features:
Single‑row design
High radial load capacity
Compact structure
Suitable for moderate speeds
Popular models:
SL185008
SL185012
SL185016
SL19 Series
Designed for applications requiring:
Higher rigidity
Greater load capacity
Improved operational stability
Primarily used in heavy‑duty industrial power transmission equipment.
NCF Series
Features:
Single‑row full‑complement design
Integrated flanges
Axial positioning capability
Main applications are industrial gearboxes and lifting equipment.
NNCF Series
The double‑row design delivers:
Higher radial load ratings
Increased rigidity
Superior shaft support
Suitable for large‑scale machinery and heavy‑duty power transmission systems.
Shaft Raceway Requirements
Since these bearings operate without an outer ring, the shaft or housing raceway becomes a core component of the bearing system.
Raceway Hardness
Recommended hardness:
58‑64 HRC
Main materials:
GCr15 (100Cr6)
High‑frequency hardened alloy steel
Carburizing hardened steel
Raceway Surface Finish
Recommended roughness:
Ra ≤ 0.2 μm
Highly polished raceways reduce friction and extend bearing life.
Dimensional Precision
Shaft raceways must be machined to precision bearing tolerance standards to ensure proper roller contact, uniform load distribution, and vibration reduction.
Lubrication Recommendations
Direct contact between rollers makes adequate lubrication essential.
Grease Lubrication
Suitable for:
Moderate speeds
Intermittent operation
Recommended greases:
EP2 lithium grease
Synthetic industrial grease
Oil Lubrication
Preferred for:
Continuous operation
High temperatures
Gearbox applications
Lubrication methods:
Oil bath lubrication
Circulating oil systems
Oil‑air lubrication
Common Failure Modes
Understanding bearing failure mechanisms helps maximize service life.
Surface Fatigue
Causes:
Excessive load
Insufficient lubrication
Contamination
Wear
Main causes:
Inadequate lubrication
Abrasive particles
Incorrect installation
Roller Smearing
Occurrence conditions:
Excessively rapid acceleration
Insufficient lubricant film
Raceway Damage
Main causes:
Shaft misalignment
Overloading
Inadequate shaft hardness
Quality Control and Inspection Standards
High‑quality full‑complement cylindrical roller bearings shall comply with the following standards:
ISO 15
ISO 492
ISO 281
DIN standards
ABMA standards
Key Inspection Items:
Dimensional Inspection
Inspection contents:
Bore diameter
External dimensions
Width tolerances
Hardness Testing
Verification items:
Ring hardness
Roller hardness
Raceway hardness
Radial Internal Clearance Measurement
Common clearance classes:
CN
C3
C4
C5
Vibration Testing
Verification items:
Smooth operation
Low noise
Consistent quality
Metallographic Analysis
Verification items:
Heat‑treatment quality
Material microstructure
Surface integrity
Why OEM Manufacturers Choose Full‑Complement Bearings
OEM equipment manufacturers are increasingly adopting full‑complement cylindrical roller bearings for the following benefits:
Higher load ratings
Longer service life
Compact machine design
Lower maintenance costs
Improved power transmission rigidity
Excellent reliability under harsh operating conditions
Demand for these high‑performance bearing solutions keeps growing across mining, renewable energy, steel production, heavy machinery and other industries.
Future Trends for Full‑Complement Cylindrical Roller Bearings
As industrial equipment becomes more powerful and compact, bearing manufacturers are developing technologies including:
Higher‑capacity roller geometries
Advanced heat‑treatment technologies
Low‑friction surface coatings
Smart bearings equipped with condition‑monitoring sensors
Optimized lubrication systems
Service‑life‑extended bearing steels
These innovations help reduce industrial downtime, boost energy efficiency and improve equipment reliability.
Conclusion
Full‑complement cylindrical roller bearings without outer rings represent one of the most effective solutions for applications requiring maximum radial load capacity, high rigidity and compact installation dimensions. Capable of enduring heavy loads, shock conditions and harsh industrial environments, they are indispensable for gearboxes, mining equipment, steel mills, wind turbines and construction machinery.
For engineers, distributors and OEM manufacturers seeking reliable heavy‑duty bearing solutions, full‑complement cylindrical roller bearings are one of the most cost‑effective and technically advanced options available on today’s industrial bearing market.