I. The "Space Constraint" Problem of Precision Equipment: Accommodating and Supporting

During the evolution of robot joint design, the contradiction between space and performance has always been a challenge that engineers need to confront. The development of modern industrial robots tends towards lightweighting, and bearings must be installed in limited space, thus requiring small size and light weight. The wrist of a six-axis industrial robot, for instance, often has a thickness of only a few tens of millimeters, yet it must accommodate a reducer, motor, encoder, wiring, and bearing. The hip joint of a humanoid robot is even more demanding - the thickness is compressed to within 30-40 millimeters. The joint space of collaborative robots is also extremely precious.

 

However, the high load-bearing capacity, high rotational accuracy, high operational stability, high positioning speed, high repeatability accuracy, long lifespan, and high reliability of robots' performance requirements necessitate that the supporting bearings must possess high load-bearing capacity, high precision, high stiffness, low friction torque, long lifespan, and high reliability.

 

There is a fundamental contradiction between "being able to accommodate" and "being able to support". Ordinary bearings increase their wall thickness to achieve higher load-bearing capacity. To achieve higher load-bearing capacity, thick-walled bearings are used, making the joint thicker; to achieve lightweighting, rigidity is sacrificed, and accuracy is compromised. Using standard general-purpose bearings is difficult to meet these requirements.

 

Typical problems of traditional bearings in the context of lightweighting:

 

Conflict between space limitation and load-bearing capacity - The installation space for the joint is limited, but it needs to withstand multi-directional combined loads. Standard bearing cross-sections are too large to install, and thin-type bearings have insufficient rigidity and load-bearing capacity.

 

Self-weight impeding dynamic response - Heavy bearings increase the joint's inertia, causing slower acceleration and deceleration responses and higher energy consumption.

 

Constriction of hollow wiring - Thick-walled bearings occupy internal space, making wiring, air tubes, and fluid tubes unable to pass through the joint, limiting design flexibility.

 

Insufficient precision retention - Ordinary thin-walled bearings experience gap drift under alternating loads, and repeatability accuracy decreases over time.

 

II. NMT High-Precision Thin-Walled Bearings: A Technological System That "Wins by Being Thin"

Unlike ordinary bearings that rely on increasing wall thickness to achieve higher load-bearing capacity, NMT's equal-section series products maintain the consistency of inner and outer ring dimensions on a very thin cross-section. NMT does not use complex external structures to compensate for the shortcomings of bearings but instead uses the simple and solid solution of equal-section thin-walled bearings to extract as much rigidity and precision as possible within the limited thickness.

 

▸ Equal-section design: Constant cross-section, uniform joints

 

The cross-section of each series of equal-section thin-walled bearings is mostly square, and the dimensions are designed as fixed values. In the same series, the cross-sectional dimensions remain unchanged and do not increase with the increase in inner diameter size.

 

This means that robot designers no longer need to repeatedly compromise between "being able to accommodate" and "being able to support" - from the wrist joint of a collaborative robot with a diameter of less than 50 millimeters to the rotating base over 300 millimeters, the same installation logic can be used. The expansion of product diversity extends its application range.

 

The true value of the equal-section design is not merely saving axial space, but rather it structurally inhibits the common gap drift phenomenon of traditional bearings. When the robotic arm accelerates or decelerates rapidly or changes directions frequently, ordinary thin-walled bearings are prone to local stress concentration due to uneven wall thickness, which affects trajectory repeatability. NMT achieves consistent rigidity response at every angle by strict channel ultra-precision processing and uniform cross-sectional control in each bearing angle. The structure with vertically crossed rollers can prevent the locking of the rollers, and at the same time, because the inner and outer rings of the bearing are segmented and the gap is adjustable, even when subjected to pressure, a high rotational accuracy can be achieved.

 

The cross-coupled roller bearing, with its lightweight composite structure, high rotational accuracy, good rigidity, and stable friction torque, is widely used in the rotating parts of industrial robots such as the waist rotation, the shoulder, arm, and wrist of joint-type robots.

 

Due to the strong ability to withstand combined loads, high precision, low friction torque, light weight, and smooth operation of thin-walled four-point contact ball bearings and thin-walled cross roller bearings, they are mostly used in the waist, elbow, and wrist parts of industrial robots.

 

▸ Thin-walled ball bearing series: deep groove ball, angular contact, four-point contact

 

The equal-section thin-walled ball bearings include the thin-walled four-point contact ball bearing series, the thin-walled angular contact ball bearing series, and the thin-walled deep groove ball bearing series. They are mostly used in the waist, elbow, and wrist parts of industrial robots that require small section sizes and restrictions.

 

The four-point contact ball bearing can withstand the combination of radial, thrust, and torque loads. Under the same inner diameter size, thin-walled equal-section ball bearings have more steel balls than standard rolling bearings, thus improving the force distribution inside the bearing, reducing the elastic deformation at the contact point between the steel balls and the groove, and enhancing the bearing's load-carrying capacity.

 

Three. Precision Manufacturing: From Micrometer Precision to 80 Million Cycle Verification

▸ P4/P5 Level High Precision Standard

 

The NMT high-precision thin-walled bearings have stable accuracy reaching the P4 level. The thin-walled precision bearings can meet the high operating precision requirements of ABEC 7F (ISO P4). The robot joint bearings need to meet the P2-P5 level precision standards. With appropriate preload, the rotational accuracy is ensured.

 

▸ Ultra-finishing and High-Precision Steel Balls

 

NMT uses ultra-finishing raceways to provide smooth surface finish and reduce internal friction and vibration. To obtain the low friction torque, high rigidity, and good rotational accuracy of the bearing, small outer-diameter steel balls are used. The steel ball precision reaches G5 level or higher, optimizing the smooth rolling performance. The thin-walled bearings achieve an extremely thin bearing cross-section, and also realize the miniaturization and lightweight of the product.

 

▸ Special Carburizing Treatment and Deep Cold Process

 

NMT selects bearings made of specially carburized steel, which maintains the low inertia advantage of the thin-walled structure while significantly enhancing the fatigue resistance of the raceway surface. The deep cold treatment process is introduced in the heat treatment stage to make the microstructure of the bearing steel more dense and stable, thus squeezing out as much rigidity reserve as possible in a few millimeters of wall thickness. NMT's equal-section thin-walled bearings adopt regional hardening treatment, with the raceway surface achieving high hardness while the base retains a certain toughness.

 

▸ 80 Million Cycle Test Verification

 

A group of NMT bearings used in the wrist of a six-axis industrial robot, after continuous 80 million cycle tests, the increase in friction torque was controlled within 12% of the initial value. This means that the equipment on the production line can maintain a stable output rhythm for a longer maintenance cycle, and for a 24-hour continuous production environment, this reliability directly translates to lower overall operating costs.

 

▸ Special Groove Design, Precision Still Maintained after Millions of Oscillations

 

The engineers of NMT use a special groove design to make the contact stress distribution between the rolling elements and the raceway more uniform, even after millions of oscillations, the initial rotational accuracy can still be maintained. In the assembly process, the laser sensor on the automated production line will conduct a full inspection of the radial clearance of each bearing to ensure that thermal expansion does not cause jamming during high-speed rotation.

 

Four. Typical Application Scenarios - Comprehensive Lightweight Precision Adaptation

▸ Industrial Robot Joints (Waist, Elbow, Wrist) Isometric thin-walled bearings and cross roller bearings are the two main categories used in industrial robot applications. They are widely applied in the waist, elbow, and wrist parts of industrial robots that require small cross-sectional dimensions. Thin-walled four-point contact ball bearings and thin-walled cross roller bearings have the characteristics of strong ability to withstand combined loads, high precision, low friction torque, light weight, and smooth operation.

 

▸ Collaborative robots (SCARA, collaborative robotic arms)

 

Isometric thin-walled bearings show high adaptability in robot joints that require both high rotational accuracy, low friction, and compact space, such as the wrists of collaborative robots and SCARA robots. NMT isometric thin-walled bearings, with lightweight design and high-precision raceways, help collaborative robots and service robots achieve high load-bearing and low error.

 

▸ Humanoid robots (shoulder, hip, wrist, etc. joints)

 

When humanoid robots attempt to perform simple actions like grasping a water cup, the thin-walled bearings in the shoulder joint need to withstand the impact of radial and axial forces in a very small space. In the leg joints of the new generation exoskeleton robots, these slender bearings are bearing the weight of the human body, making assisted walking more natural and smooth. Humanoid robots have more than 50 joints, and some installation spaces are only 5mm wide. NMT's minimum cross-sectional thickness of 2.5mm micro thin-walled bearings are suitable for joints with limited space, such as dexterous hands and necks.

 

▸ Precision turntables and rotating worktables

 

Cross roller bearings are widely used in high-precision rotating tables, robot joints, rotating units, and precision medical equipment. Thin-walled cross roller bearings with their lightweight composite structure, high rotational accuracy, good rigidity, and stable friction torque are widely used in rotating worktables of machining centers, rotating parts of robotic hands, and precision rotating worktables.

 

▸ Semiconductor and medical equipment

 

Precision thin-walled bearings play a key role in semiconductor equipment, measurement systems, and medical imaging equipment. Thin-walled bearings are also important in medical equipment such as surgical robots, CT scanners, and prosthetics. NMT's special lubricant neither volatilizes particles nor maintains sufficient lubrication at low torque.

 

▸ AGV/AMR hubs and steering systems

 

Thin-walled bearings are used in AGV/AMR hubs, suitable for occasions where space and weight are crucial.

 

V. Precision Quality Control - Full Chain Linkage Guarantee from Materials to Finished Products

NMT has invested decades in the purity control of bearing steel, using vacuum degassing treatment to control non-metallic inclusions at extremely low levels. This almost obsessive quality control ensures that NMT bearings can achieve micrometer-level repetitive positioning accuracy in daily assembly tasks in robot joint modules.

 

NMT's approach is to introduce cryogenic treatment in the heat treatment process, making the microstructure of bearing steel more dense and stable, thus squeezing out as much rigidity reserve as possible in a few millimeters of wall thickness. When six-axis robots are fully loaded and running at high speed, the slight elastic deformation between the inner and outer rings of the bearings will be precisely controlled within a very narrow window.

 

NMT achieves consistent rigidity response in every angle through strict channel ultra-finishing and uniform cross-sectional control. This characteristic is particularly important for high-value-added applications such as precise gluing and optical inspection - even after millions of reciprocating movements, the joints can still output smooth and predictable rotational actions.

 

VI. Stock Piling + Non-standard Customization - Quick Response to Customer Needs

Common thin-walled bearing models (isometric thin-walled bearings, cross roller bearings, thin-walled angular contact ball bearings) are in stock - covering 80% of the thin-walled bearing requirements for robot joints, precision turntables, and semiconductor equipment. Emergency orders are dispatched on the same day, minimizing delivery lead times. Customizable items - Special inner and outer diameters/widths, customized precision grades (P4/P5), customized clearance, special materials (stainless steel/chromium steel), special sealing structures, thin-walled deep groove ball type (C type)/angular contact type (A type)/four-point contact type (X type) are available.

 

Quick prototyping with old bearings or drawings - Small batch urgent orders can be delivered quickly. Affordable replacement for imported brands (SKF, FAG, NSK, NTN, IKO, THK, Kaydon), significantly reducing procurement costs.

 

VII. Factory simulation condition testing - Stable operation of precision equipment is guaranteed

All products undergo four special tests before leaving the factory:

 

Alternating load fatigue life test - Simulates the frequent start-stop and load changes of robot joints to verify the fatigue resistance of the bearings

 

High-speed rotation accuracy test - Detects the rotation accuracy and vibration values of the bearings at the rated speed to ensure P4/P5 accuracy standards are met

 

Friction torque stability test - Detects the fluctuation of friction torque during continuous operation of the bearings to ensure low friction and low heat generation

 

Accuracy and clearance detection - Sequentially tests the inner diameter, outer diameter, width, radial clearance and rotational accuracy to ensure consistency

 

Defective products are all scrapped. Bearings of the same batch are highly consistent in size, accuracy and torque, facilitating unified management and planned replacement of spare parts by robot manufacturers and precision equipment manufacturers.

 

VIII. Life cycle cost optimization - Higher precision leads to lower overall costs

Choosing thinner-walled bearings with higher precision may result in a slightly higher purchase price, but the overall holding cost is significantly lower. In robot joints, the precision and reliability of the bearings directly determine the motion quality, repeatability positioning accuracy and service life of the entire machine.

 

Hidden costs of low-cost ordinary thin-walled bearings:

 

Gap drift leads to a decrease in repeatability positioning accuracy, and the accuracy becomes out of control after half a year

 

Uneven wall thickness causes local stress concentration, and the raceways peel off prematurely

 

Unstable friction torque, increasing robot energy consumption and making movements uneven

 

Frequent replacements lead to production line shutdowns, affecting production rhythm

 

The NMT high-precision thin-walled bearings have a stable service life of 40,000-50,000 hours (about 5-6 years) in industrial robot joints, collaborative robots, and precision turntables:

 

The replacement frequency is reduced by more than 60% - The number of unplanned shutdowns per year is significantly reduced, ensuring production line efficiency

 

Uniform cross-section design inhibits gap drift - Long-term consistent rigid response, stable repeatability positioning accuracy

 

P4/P5 grade precision ensures motion quality - Robot movements are smooth and precise, suitable for high-value applications such as precision coating and optical inspection

 

Special carburizing treatment enhances fatigue resistance - The incremental increase in friction torque after 80 million cycles is controlled within 12%

 

Companion components (reduction gears, motors, housings) have a longer lifespan - The overhaul cycle of the entire machine is extended, and the overall holding cost is significantly reduced

 

For robot manufacturers, precision equipment manufacturers, semiconductor equipment enterprises and automation system integrators, the comprehensive holding cost of NMT high-precision thin-walled bearings is much lower than the repeated replacement cost of cheap bearings - What is saved is not the difference in bearing prices, but the long-term stable precision and motion quality reliability of the operating certainty of precision equipment.