1 The structure and working principle of NMT cylindrical roller bearings

Cylindrical roller bearings are the core members of the rolling bearing family, known for their superior radial load-carrying capacity. Their basic structure consists of an inner ring, an outer ring, cylindrical rollers, and a cage. Unlike the point contact of ball bearings and angular contact ball bearings, the rollers of cylindrical roller bearings have a line contact or modified line contact with the raceways, resulting in a larger contact area and more uniform stress distribution. The radial load-carrying capacity of a single-row cylindrical roller bearing is 1.5-3 times higher than that of ball bearings of the same size.

 

NMT cylindrical roller bearings offer various structural forms such as single-row, double-row, and full-load roller designs. The single-row cylindrical roller bearing adopts a separable structure, with the inner ring or outer ring being able to be disassembled independently, greatly facilitating installation and maintenance. The full-load roller design eliminates the cage, allowing for more rolling elements to be accommodated within the same size dimensions, further enhancing the radial load-carrying capacity.

 

The cage of NMT cylindrical roller bearings is made of high-strength copper alloy or precision molded thermoplastic polyimide. The copper alloy cage maintains the stable posture of the rolling elements under variable loads; the thermoplastic polyimide cage has an extremely low wear rate and maintains stable dimensions in high and low temperature cycles.

 

In terms of application versatility, NMT provides various edge configurations such as NU type (outer ring without flange), NJ type (outer ring with single flange), and NUP type (outer ring with double flanges) to accommodate different axial displacements and positioning requirements. NMT cylindrical roller bearings use vacuum degassing high-carbon chromium bearing steel, with the raceways hardened by carburizing and quenching, forming a high-hardness anti-fatigue layer on the surface, while maintaining toughness in the core to absorb impact without cracking. The wide temperature range lubricating grease maintains stable lubrication performance within the range of -45°C to 155°C.

 

2 Core performance advantages of NMT cylindrical roller bearings

First, excellent radial load-carrying capacity. The line contact structure between the cylindrical rollers and the raceways gives the bearing its inherent high radial stiffness. NMT achieves this through asymmetric logarithmic shaping, with the contact stress of the rollers and raceways gradually decreasing from the center to the ends, rather than being concentrated on the outer side, effectively eliminating edge stress concentration. In the thousands of full-load rotations per day of the stack robot, this detail directly manifests as the bearing life moving from "acceptable" to "predictable".

 

Second, the full-load roller design further enhances the load-carrying limit. In scenarios such as the wrist joint of heavy-load six-axis robots with limited space and complex stress conditions, NMT adopts the full-load roller design, eliminating the cage and accommodating more rolling elements within the same size dimensions, significantly enhancing the radial load-carrying capacity. To address the problem of friction between the full-load rollers, NMT introduces tiny spherical protrusions on the roller end faces, converting the line contact into point contact, while combining it with specially formulated extreme pressure lubricating grease to form an isolation oil film.

 

Third, roller attitude control and self-centering guidance. NMT optimizes the contact geometry between the roller end faces and the flange to construct a self-centering guiding surface, enabling the rollers to automatically correct attitude deviations during operation. The gap between the retaining holes of the retaining ring and the rollers is precisely controlled, providing sufficient clearance for free rolling while limiting the accumulation of skew angles. In the high-frequency reciprocating motion of the robot, the rollers always enter the bearing area in the optimal posture, and the wear of the raceways is more uniform and controllable.

 

Fourth, microfluidic hydrodynamic effect ensures low-speed lubrication. NMT introduces regular-distributed micron-sized oil storage pits on the raceway surface. When the rolling elements pass through, the microfluidic hydrodynamic effect is generated, forcing the stored lubricating oil into the contact area. The surface of the rollers is specially treated with hydrophilic properties, allowing oil molecules to firmly adhere to the metal surface and form a boundary lubrication film. During the low-speed crawling or frequent forward and reverse rotations of the assembly robot, the bearing contact surface is always in an effectively lubricated state.

 

Fifth, hollow rollers and lightweight design. NMT adopts a hollow roller structure, significantly reducing the mass of a single roller while maintaining radial rigidity. Combined with high-strength lightweight cage materials, the overall rotational inertia of the bearings is significantly reduced, making them suitable for precise transmission scenarios with requirements for response speed.

 

Sixth, vacuum cleanliness and low dust emission characteristics. NMT upgrades the cage material of cylindrical roller bearings to precision molded thermoplastic polyimide. The raceways and rollers undergo chemical polishing to eliminate machining burrs and microscopic peaks. Combined with fluorinated polyether lubricant, the bearings produce almost no precipitates during vacuum high-temperature baking processes. After long-term continuous operation of wafer transfer robots, the particle count in the surrounding environment still meets the most stringent standards.

 

3 Main industrial application scenarios of NMT cylindrical roller bearings

3.1 Heavy-duty industrial robot joints

 

In the core joints of heavy-duty handling robots, stacker robots, and welding robots, cylindrical roller bearings play the role of "load-bearing walls". NMT cylindrical roller bearings enhance the lifespan and stability of heavy-duty robot joints through asymmetric shaping and high rigidity design. In the wrist joint of heavy-duty handling robots, NMT optimizes the sliding contact conditions between the roller end face and the guard edge to maintain the stability of the rolling body under variable loads.

 

3.2 Machine tool spindles and precision grinding equipment

 

The rotational accuracy of machine tool spindles directly determines the surface quality of the workpiece. NMT uses the online closed-loop grinding process with multiple-point measurement to compress the roundness error of the raceway to the sub-micron level. Performing harmonic analysis on the waviness of the raceway and deliberately weakening specific order waves that are prone to resonance. Combined with the group-matched high-precision rollers, the radial runout of the bearings presents a random and low-amplitude distribution.

 

3.3 Large motors and generators

 

Large and medium-sized motors, generators, and other equipment need to withstand huge radial loads. The line contact structure and high radial stiffness of NMT cylindrical roller bearings provide stable support for the rotors of large rotating equipment, ensuring the reliability of the equipment during continuous high-load operation. The separated structure enables the replacement of bearings in large motors without disassembling the entire rotor, significantly improving maintenance efficiency.

 

3.4 Construction machinery and mining equipment

 

Excavators, cranes, crushers, and other construction machinery are subjected to intense impact loads. The raceway carburizing and quenching treatment of NMT cylindrical roller bearings, combined with the high-hardness anti-fatigue layer and the ductile core, enables them to absorb impacts without cracking. The thick-walled outer ring structure provides excellent impact resistance and high radial load-bearing capacity.

 

3.5 Semiconductor and clean environment equipment

 

In scenarios with extreme cleanliness requirements such as wafer transfer robots and vacuum coating equipment, NMT cylindrical roller bearings' low dust emission and low precipitate characteristics make them a reliable choice. The thermoplastic polyimide cage combined with fluorinated polyether lubricant produces almost no pollutants in a vacuum high-temperature environment.

 

3.6 Food packaging and rinsing environment equipment

 

Parallel robots on food packaging production lines face frequent high-pressure rinsing tests. NMT cylindrical roller bearings adopt an integrated sealing structure, combining two labyrinth seals and one contact seal. The cage uses FDA-certified engineering plastics, fundamentally eliminating the risk of introducing foreign substances due to cage wear.

 

4 Installation, operation and maintenance guidelines

4.1 Key points for structural selection

 

Load capacity selection: Select cage type for standard radial load; choose full-roller type (without cage) for extreme radial load.

 

Axial displacement requirements: NU type (outer ring without guard edge) - allows bidirectional axial displacement of the shaft and bearing housing; NJ type (outer ring with single guard edge) - allows one-way axial displacement and can withstand certain axial force; NUP type (outer ring with double guard edges) - can withstand bidirectional axial force and perform axial positioning.

 

Accuracy grade selection: General transmission selects standard accuracy; for precision scenarios such as machine tool spindles, select P5/P4 grades. Sealing method selection: Open type is suitable for circulating oil lubrication; Sealed type pre-fills lubricating grease, suitable for maintenance-free scenarios.

 

4.2 Installation precautions

 

The cylindrical roller bearing is of a separable structure. During installation, the inner ring and the outer ring can be assembled separately. When installing, use special tools to evenly transfer the force to the rings. It is strictly prohibited to directly strike the rolling elements or the cage. When installing a fully loaded cylindrical roller bearing, special attention should be paid to the arrangement direction and uniform distribution of the rollers. After installation, it is necessary to detect the radial runout and axial clearance to ensure compliance with design requirements.

 

4.3 Lubrication management suggestions

 

Sealed bearings pre-filled with lubricating grease generally do not require mid-term replenishment of grease. Open cylindrical roller bearings need to replenish lubricating oil or grease according to the maintenance cycle. For heavy-load and low-speed scenarios, extreme pressure lubricating grease is recommended; for high-speed scenarios, the filling amount of lubricating grease should be strictly controlled. For humid or corrosive environments, lubricants resistant to hydrolysis and rust prevention are recommended.

 

4.4 Daily inspection items

 

Regularly monitor the running noise and bearing temperature. Persistent sharp abnormal sounds usually indicate insufficient lubrication or damage to the raceway. Regularly check the condition of the sealing components to prevent water and dust from entering and causing corrosion of the raceway. The high-precision manufacturing and strict quality control of NMT cylindrical roller bearings ensure that they can achieve a long service life of over tens of thousands of hours under normal use conditions.

 

5 The import substitution value and supply chain advantages of NMT cylindrical roller bearings

High-end equipment manufacturers such as heavy-load industrial robots, machine tool spindles, and large motors have a continuous and rigid demand for high-precision cylindrical roller bearings. For a long time, the high-precision cylindrical roller bearing market has been dominated by overseas brands, with problems such as long supply cycles, high unit prices, and slow response times for supporting services.

 

Japanese NMT cylindrical roller bearings strictly follow international precision manufacturing standards for production. Core indicators such as radial load capacity, rotational accuracy, and fatigue life can rival those of imported top brands, meeting the dual needs of new machine batch assembly and maintenance spare parts. The external dimensions strictly follow international standards, achieving complete interchangeability with existing imported bearings without any additional processing or structural modifications. General models have a large inventory of spare parts in stock, capable of meeting emergency repairs and bulk procurement needs, effectively reducing the pressure on enterprises' spare parts inventory.

 

High-quality NMT cylindrical roller bearings provide reliable radial support for key transmission parts such as industrial robot joints, machine tool spindles, and large motors, ensuring the long-term stable operation of equipment under heavy-load and high-precision conditions.

 

NMT supports temperature-adaptive substrate selection, thermal stability structure optimization, wide temperature range lubrication customization, and special structural non-standard customization. Main size specifications have ready-made inventory, installation dimensions follow industry standards, and can be directly replaced with imported similar products.