What Is a Crossed Roller Ring?
Crossed roller rings are bearing components that can support loads in various directions simultaneously, such as radial, axial, and moment loads.
It is ring-shaped in appearance. Multiple cylindrical rollers are arranged in series alternately in the ring through spacer retainers on the 90° V-groove shaped rolling surfaces, so that loads from various directions can be supported.
Uses of Crossed Roller Rings
Crossed roller rings are used in many industrial machines. The range of uses is wide, including joints and swivel sections of industrial robots, swivel tables of machining centers, manipulator swivel sections, precision rotary tables, medical equipment, measuring instruments, and IC manufacturing equipment, to name a few. The wide range of uses of our products can be attributed to the following advantages:
- Excellent Rotation System
Prevents roller skew and increases rotational torque due to mutual friction between rollers. - Stable Rotational Torque
Stable rotational torque can be obtained even when pressurization is applied, resulting in high support rigidity and highly accurate rotational motion. - Easy to Handle
Principle of Crossed Roller Rings
Crossed roller rings can support loads in various directions because the rollers are arranged alternately at a 90° angle. Since rollers are used as rolling elements, large loads can be supported.
Also, since the rollers are arranged in alternating rows perpendicular to each other, the cross rollers can support loads from various angles.
Types of Crossed Roller Rings
There are six main types of crossed roller rings:
1. RU Type
Since the RU type has a seated structure with integral inner and outer rings, there is virtually no effect on performance due to assembly, and the rotational accuracy and torque are stable. The RU type is also characterized by the fact that it does not require a flange housing.
2. RB Type
The RB type is the basic form of crossed roller rings, in which the outer ring is divided into two parts and the inner ring is a single piece. It is characterized by the fact that it is used where rotational precision is required in the inner ring.
3. RE Type
The RE type has the same dimensions as the RB type, but this type is used where the rotational accuracy of the outer ring is required.
4. RB/RE Type-USP Series
The RB/RE type-USP series exceeds the world’s highest accuracy standards and is a top class in precision.
5. RA Type
The RA shape has the thinnest possible thickness of the inner and outer rings of the RB shape.
6. Type RA-C
The RA-C type has the same dimensions as the RA type, but can also be used for outer ring rotation. The RA-C type has a one-part split outer ring structure and features high rigidity, even for the outer ring.
Other Information About Crossed Roller Rings
1. Installation of Crossed Roller Rings
The wall thickness of the housing in which the crossed roller rings are mounted must be determined in consideration of the rigidity of the part. Insufficient strength will cause deformation of the bearing and uneven roller contact inside, leading to premature breakage and deterioration of rotational accuracy.
The wall thickness of the housing should be designed to be at least 60% of the cross-sectional height of the crossed roller ring. In addition, if a tapped hole is drilled for removal, the crossed roller ring can be removed without putting a load on it, preventing damage at the time of removal.
When installing the push flange to secure the crossed roller ring, the order in which the bolts are tightened is also important. In order to tighten the bearings evenly, it is important to tighten the diagonal screws little by little and assemble them so that the tightening is uniform.
Thus, when using a high-precision rotating mechanism, it is necessary to pay attention not only to the machining accuracy of the crossed roller rings but also to the machining accuracy of the mounting parts and the assembly method.
2. Pressurized Crossed Roller Rings
Crossed roller rings can be pressurized in the same way as ordinary ball bearings. Applying pressurization increases the support of rigidity and rotational accuracy. On the other hand, since rotational friction increases, care must be taken when calculating rotational power.
Pressure is usually applied by setting the radial clearance to a negative value. The recommended dimensional tolerance of the housing and shaft to which the crossed roller ring with applied pressure is attached is g5/H7, and the fit must be set so that the ring does not clamp. If the fit is tightened, the internal stress will be high due to excessive pressure, which may cause breakage.