What is thin section four-point contact ball bearing?

What is thin section four-point contact ball bearing?

Four-point contact ball bearings are a kind of separating bearings, which can also be said to be a set of angular contact ball bearings that can bear bidirectional axial loads. The inner and outer ring raceways are peach-shaped cross-sections, and when there is no load or pure radial load, the steel ball and the ferrule are in four-point contact, which is also the origin of this name. When only the pure axial load is acted, the steel ball and the ferrule become two points of contact, which can withstand the axial load in both directions. Four-point contact ball bearings can also withstand moment loads and function as both single-row angular contact ball bearings and double-row angular contact ball bearings.

Features of four-point contact ball bearings

Four-point contact ball bearings are separable constructions, and a single bearing can replace the angular contact ball bearings with a frontal or backside combination.

It can withstand radial loads and bidirectional axial loads, which can limit the axial displacement in both directions, but occupies less axial space than the current specifications of double-row angular contact ball ball bearings.

Compared with other ball bearings, four-point contact ball bearings have smaller axial clearance and higher limit speed when the radial clearance is the same.

Four-point contact ball bearings are suitable for bearing pure axial loads or combined axial and radial loads dominated by axial loads. Because it is a double half inner ring (or outer ring), the number of balls is increased, and it has a large bearing capacity.

Under normal working conditions, when this type of bearing bears axial load in any direction, it can form a contact angle, and the steel ball is in contact with the inner and outer raceways at one point to avoid large sliding friction in the contact area. Therefore, the bearing should not bear the radial force and load.

The working principle of thin-knuckle four-point contact ball bearings

Mechanical properties of four-point contact structures

Gothic raceway design

The inner and outer ring raceways of the bearing adopt a double semi-circular arc structure (similar to a Gothic pointed arch), each steel ball forms two contact points with the inner and outer rings, and the four points of contact form a diamond-shaped stress distribution. This design allows the bearing to withstand radial loads, bidirectional axial loads and overturning moments at the same time, and its axial load carrying capacity is about 30% higher than that of single row angular contact ball bearings, which can be equivalent to two sets of back-to-back mounted angular contact ball bearings.

Dynamic adjustment mechanism of contact angle

The standard contact angle is 35°-45°, and when subjected to a combined load, the steel ball generates a small displacement in the raceway, and the load is redistributed by dynamic adjustment of the contact angle. For example, in industrial robot joints, the bearing automatically optimizes the distribution of contact points based on changes in the attitude of the end effector, ensuring sub-micron positioning accuracy.

Lightweight innovation for thin joint structures

Section downgauging technology

By optimizing the ratio of ball diameter to raceway radius of curvature (typically 0.55-0.65), the bearing height can be reduced by 20%-30% while maintaining strength. In the case of Type 6204 bearings, for example, the thin-knot design reduces the axial height from 15mm to 10mm, reducing weight by 40% and significantly saving installation space.

Material properties are strengthened

Carburized bearing steels (e.g. GCr15SiMn) or ceramic balls (Si3N4), combined with a vacuum quenching process, allow the thin knot structure to withstand 1.5 times the rated dynamic load. For example, ceramic ball bearings for fuel pumps in aero engines operate reliably at speeds up to 20,000 rpm.

High-speed dynamic response optimization

Moment of inertia control

The thin-knuckle design reduces the bearing mass distribution radius, resulting in a reduction in moment of inertia of approximately 30% and a DN value (diameter × speed) of 1.5×10⁶. In semiconductor wafer dicing machines, this feature ensures a spindle start-up time of as little as 0.3 seconds and a 40% increase in response frequency.

Friction and temperature rise suppression

The high-precision polishing raceway (Ra≤0.1μm) combined with oil-air lubrication technology controls the friction coefficient at 0.001-0.003, which is 15°C lower than the temperature rise of traditional lubrication methods. In a high-speed centrifuge, for example, the temperature rise of the bearings after 100 hours of continuous operation is only 12°C.

Composite Load Transfer Mechanism

Couple balancing system

When subjected to bidirectional axial loads, the upper and lower rows of contact points form a couple, which counteracts the torque through the internal structure of the bearing. In precision machine tool spindles, for example, the design allows axial channeling to be controlled within ±2 μm, which is better than ISO P4 standards.

Stiffness enhancement effect

The four-point contact space rigid frame structure increases the radial stiffness of the bearing by 25%, supports a 500kg load in a precision rotary table, and maintains a rotation accuracy of 0.5 arc seconds.

Applications of thin-knot four-point contact ball bearings

With its unique four-point contact structure and thin-walled design, thin-section four-point contact ball bearings show irreplaceable advantages in many fields:

Industrial automation field

Widely used in the waist, elbow and wrist joints of industrial robots, its isocross-sectional design (such as 4.7625mm standard cross-section) makes different bore bearings compatible with installation, the axial width is only 50% of that of traditional bearings, but can withstand ±2000N axial force and 500N・m overturning moment. For example, the UR10e robot uses ceramic ball bearings at the end, which has a repeatability of 0.02mm and a life of more than 2000 hours.

Medical & Semiconductor Devices

In surgical robots, customized bearings (contact angle 40°) can achieve 7 degrees of freedom movement in a space with a diameter of 40mm, with a friction coefficient of ≤ 0.0015, and the spindle bearing of the semiconductor wafer cutting machine (DN value 1.5×10⁶) supports high-speed rotation of 20,000 rpm with a temperature rise of 12°C. Medical-grade stainless steel or ceramic coating materials meet biocompatibility requirements.

New Energy and Transportation

The electric steering bearings control the axial movement of ±2 μm through the double-curvature raceway design, and the wind turbine pitch bearings (1.8 m diameter) can withstand 12 MN axial forces and 80 mn・m overturning moments for up to 20 years. The price of domestic alternative models is only 1/3 of that of imports, and they have been applied in batches in the field of wind power.

Aerospace & Precision Equipment

Aero engine fuel pump bearings are made of ceramic balls and carburized bearing steel, which can operate stably from -55°C to +150°C; Satellite reaction wheel bearings achieve a 15-year in-orbit life by vacuum ion silver plating technology. The 5-axis machining center spindle bearing has a radial runout ≤ of 0.002mm and supports 40,000rpm high-speed milling.

The price of thin-knot four-point contact ball bearings

The price of thin-knot four-point contact ball bearings varies depending on a number of factors, such as the size of the bearing, accuracy class, material, brand, and quantity purchased. Here are some examples of price ranges in common situations:

Small ordinary precision thin-section four-point contact ball bearings, with an inner diameter of about 10mm - 20mm, the price of a single may range from tens of yuan to hundreds of yuan. For example, some ordinary precision bearings with an inner diameter of 15mm, an outer diameter of 35mm, and a thickness of 10mm may cost around 50-150 yuan.

Medium-sized bearings with an inner diameter of 20mm - 50mm are usually priced between 100 and 500 RMB. For example, the price of a bearing with an inner diameter of 30mm, an outer diameter of 62mm, and a thickness of 16mm may be around 200-400 yuan.

Large or high-precision thin-knuckle four-point contact ball bearings will be more expensive. Bearings with an inner diameter greater than 50mm and a higher accuracy class (such as P4, P2) may range in price from a few hundred to several thousand yuan. For example, the price of a high-precision bearing with an inner diameter of 80mm, an outer diameter of 150mm, and a thickness of 35mm may be around 1000-3000 yuan.

If it is a thin four-point contact ball bearing made of special materials, such as ceramic materials, the price will be much higher than that of ordinary bearings. At the same time, the price of well-known brand bearings will be relatively high due to their reliable quality and advanced technology. In addition, when purchasing large quantities, there may be a certain discount, and the price will be relatively lower.

Supplier of thin-joint, four-point contact ball bearings

As a benchmark enterprise in the field of precision transmission, LTZC is deeply engaged in the R&D and manufacturing of thin-joint four-point contact ball bearings, relying on independent innovation of Gothic raceway technology and thin-walled technology, to provide global customers with high-load, lightweight bearing solutions. The core products include QJF series (for industrial robots), KF series (medical device grade) and customized models, which are made of GCr15 bearing steel, 316L stainless steel and Si3N4 ceramic ball material, with an accuracy of P2 grade, and an axial width of only 50% of that of traditional bearings, but can withstand bidirectional axial loads (up to 2000N) and 500N・m overturning moments. Typical applications include: UR10e robot joint (0.02mm repeatability), CT machine slip ring bearing (80% longer life), semiconductor wafer cutting machine spindle (20,000rpm stable operation), etc., to help high-end equipment achieve performance breakthroughs.

LTZC's ISO 9001/13485 certified intelligent production line realizes the whole process control (Ra ≤0.1μm) from vacuum quenching of materials to precision polishing of raceways. We not only provide standard products, but also optimize the contact angle (35°-45°), sealing form (double lip/labyrinth) and preload design according to customer needs, such as the customized 1.8m diameter bearing for wind power pitch system, which can withstand 12MN axial force and 80MN・m overturning moment. With the high cost performance of domestic bearings (the price is only 1/3 of that of imported brands) and the 7×24-hour quick response service, LTZC has served 500+ customers around the world, including industrial robot head enterprises, tertiary hospitals and semiconductor equipment manufacturers. By choosing LTZC, you will receive one-stop support from selection simulation to full life cycle maintenance, and jointly promote China's high-end bearing technology to the international frontier!