A revolutionary concept from THK is set to help manufacturers and end users of automation, robotics and process systems make significant improvements to machine performance and reliability in complete motion.  As part of this concept the company’s latest RA, RB and RE cross roller bearings can be used to replace traditional angular contact ball bearing mechanisms, providing up to four times the level of stiffness, far greater rotational accuracy and the ability to handle high loads for all systems where rotation of up to or multiples of 360° is required, within the low to medium speed range.

Unlike traditional mechanisms, possibly where angular ball bearings are in face to face contact, the RA and RB cross roller bearings use an innovative method of construction, with a sequence of cylindrical rollers being arranged at right angles to each other within a sealed 90° V-groove.  This forms part of a twin ring construction, with the two rings rotating independently, with individual rollers being separated by precision formed spacer retainers, designed to locate and securely hold each roller in the correct alignment during operation, while maximising on the ability of each roller to use its full line contact.

This system has a number of key advantages: the crossed roller arrangement allows loads in all directions to be handled from a single bearing, while the cylindrical rollers provide greater contact area so that load capacities can be significantly increased.  In addition, rotational stability, smoothness and accuracy are all enhanced, noise and frictional losses are reduced and roller skew is eliminated.  The bearings require no adjustment and can be supplied preloaded for maximum rigidity.

The RA is an ultra thin, lightweight and low profile cross roller bearing and has been developed for lower load bearing applications, where high levels of stiffness are required, such as joints and swivelling parts in robotics systems, precision rotary tables, medical equipment and coordinate measuring machines.  A range of sizes are available, from 50 mm to 200 mm (inner ring diameters).

Alternatively, type RE bearings are designed with a split inner ring, for outer ring rotation.

The RB roller bearings have a split outer ring and single inner ring, producing exceptionally high levels of rotational accuracy for applications where precise inner ring rotation is required.  Sizes range from 20 mm to 1250 mm (inner ring diameters).

The latest cross roller bearings are supplied ready to install, with inner and outer rings and rollers ready assembled.  Fitting is therefore quick and simple, requiring only appropriate support mechanisms, with subsequent maintenance being restricted to occasional lubrication.