Experimental Comparison of Stiffness Between Crossed-Roller Bearings and Angular Contact Ball Bearings

The rotational accuracy and load-carrying capacity of precision machinery largely depend on the stiffness performance of bearings. Crossed roller bearings and angular contact ball bearings, two common types of precision bearings, are widely used in industrial robots, CNC rotary tables, medical equipment, and other applications. However, differences in stiffness directly affect the deformation and dynamic response of these devices under complex operating conditions. Based on empirical testing and grounded in their structural principles, this paper compares the stiffness characteristics of these two bearing types to help engineers make more informed selection decisions. Jiu Liang Bearings has long been engaged in the research, development, and manufacturing of precision bearings; the test data presented below are derived from its in‑house laboratory and carry practical reference value.

I. The Core Significance of Stiffness in Precision Rotating Components
Bearing stiffness is defined as the ratio of the load applied to the bearing to the resulting elastic deformation. For applications demanding high positioning accuracy and low vibration—such as machine tool spindles and rotary tables in semiconductor equipment—insufficient stiffness can lead to machining errors, increased vibration, and even reduced service life. The structural design differences between crossed roller bearings and angular contact ball bearings result in markedly distinct stiffness characteristics when subjected to loads in different directions. Understanding these differences is essential for accurate bearing selection.

II. Working Principles and Stiffness Characteristics of Crossed-Roller Bearings and Angular Contact Ball Bearings

2.1 Structure and Stiffness Advantages of Crossed-Roller Bearings
Crossed roller bearings feature cylindrical rollers arranged in a 90-degree crossed configuration, with the rollers separated by a cage. This design enables multi-point contact between the rollers and raceways under radial loads, axial loads, and overturning moments, resulting in a large contact area and minimal elastic deformation. Jiu Liang Bearings has implemented targeted design improvements in ultra-precision raceway finishing and optimized roller crowning, further enhancing contact stiffness. Test results show that, for the same external dimensions, the overturning stiffness of crossed roller bearings can exceed twice that of angular-contact ball bearings.

2.2 Structural Features of Angular Contact Ball Bearings
Angular contact ball bearings transmit loads through the contact between steel balls and the raceway grooves of the inner and outer rings, and are typically used in pairs to handle combined loads. Due to the small contact area and concentrated contact stresses, the steel balls are more prone to elastic deformation under load. Furthermore, the contact angle of angular contact ball bearings—typically 15°, 25°, or 40°—determines the ratio of axial to radial stiffness; however, overall, the stiffness of an individual bearing is limited by the ball diameter and the curvature radius of the raceways. In applications requiring high overturning stiffness or the transmission of large torques, angular contact ball bearings often need to be configured in multiple sets to meet the requirements, thereby increasing system complexity.

III. Comparative Experimental Measurement of Stiffness: Methods and Key Findings
3.1 Test Conditions and Plan
Juliang Bearings selected cross-roller bearings (model CRB‑0512) and angular-contact ball bearings (mounted in pairs, model 7205C/DF), both with identical inner diameter, outer diameter, and width, as the test specimens. A hydraulic loading system was used to apply radial, axial, and overturning loads, while high‑precision displacement sensors measured the relative displacements of the bearing rings, enabling the calculation of stiffness values in each direction. The tests were conducted under constant temperature conditions, with each load condition repeated three times and averaged.

3.2 Comparison of Measured Results
Radial Stiffness: The radial stiffness of crossed roller bearings is approximately 40% higher than that of angular contact ball bearings. This is because cylindrical rollers make line contact with the raceways, whereas steel balls have point contact; the former exhibits smaller contact deformation.
Axial stiffness: Crossed roller bearings exhibit approximately 60% higher axial stiffness. Their vertically arranged rollers can simultaneously accommodate axial loads in both directions, with a more uniform distribution of contact points.
Overturning stiffness: This is a key performance indicator where the two types differ markedly. The overturning stiffness of a crossed-roller bearing is nearly 2.8 times that of an angular-contact ball bearing, as the cross‑arranged rollers effectively counteract raceway deflection caused by applied moments.
Total deformation: Under the same combined load (radial + axial + overturning), the total elastic displacement of a crossed roller bearing is only about 45% of that of an angular contact ball bearing.
It should be noted that angular contact ball bearings offer superior thermal stability at high speeds and are more cost‑effective; however, when stiffness is the primary design criterion, crossed roller bearings provide a distinct advantage.

IV. Selection Recommendations: Matching Application Scenarios Based on Stiffness

When the primary loads on a device are dominated by combined radial and axial forces, and high positioning accuracy under overturning moments is required—such as in industrial robot joints, precision rotary tables, or machine tool spindles—crossed roller bearings are the more suitable choice. Jiu Li Bearings has accumulated numerous process technologies in the field of crossed roller bearings, enabling it to offer a wide range of precision grades and preload options to meet diverse stiffness requirements. Meanwhile, for applications involving extremely high rotational speeds, light loads, and cost sensitivity—such as high-speed spindles or small indexing tables—angular contact ball bearings, when properly configured, can also deliver satisfactory stiffness performance.

In summary, cross-roller bearings and angular-contact ball bearings exhibit fundamentally different stiffness characteristics. Comparative measurements clearly demonstrate that, in precision applications requiring high stiffness, superior resistance to overturning, and minimal elastic deformation, cross-roller bearings offer distinct performance advantages. When selecting a bearing, it is essential to consider the load type, rotational speed, space constraints, and cost-effectiveness; if necessary, consult the technical team at Jiuliang Bearings for more detailed recommendations on bearing selection and matching.