Robotics is a market with high growth potential. In industry, flexible and autonomous robot systems will take over both monotonous and complex tasks, relieve the burden on humans and increase productivity. In particular, lightweight robots and collaborative robots, known as cobots, have already found their way into modern automation and production systems. However, the high demands on load capacity, dynamics and precision that prevail in industry also place high demands on the components that are installed in the robots, especially bearings and gears.
Schaeffler is launching the new XZU angular contact needle roller bearing specifically for use in robot and cobot joints. It also serves as the main bearing support for the newly developed RTWH precision gearbox.

Double-row angular contact needle roller bearing

The XZU angular contact needle roller bearing from Schaeffler is used in lightweight robots and collaborative robots both as an articulated arm bearing and as the main bearing arrangement for the RTWH precision gearbox.

© Schaeffler

The company uses needles as rolling elements in the new bearing. Thanks to the X arrangement of the cage-guided needles in two raceways, the XZU not only has an increased number of load-bearing rolling elements, but also support distances. This has made it possible to increase the rigidity compared to crossed roller bearings. The contact angle is 45°.

The double-row raceway arrangement has been adapted to the requirements of robotics. According to the company, the advantages include up to 25 % higher rigidity compared to crossed roller bearings, minimized resonance and lower friction. It was also possible to improve the repeat accuracy and reduce the installation space.

Novelty in the gearbox

The RTWH precision gearbox is characterized by zero backlash, positioning accuracy, compactness and a long service life. The gear unit from Schaeffler is ready to install.

© Schaeffler

Another new product is the RTWH precision gearbox, which also uses the XZU double-row angular contact needle roller bearing. The ready-to-install reduction gearbox is a shaft gearbox in 'Silk Hat' design. This means that the gearbox is characterized by zero backlash, high positioning accuracy and wear resistance. These properties, which are particularly important for robotics, result in a long service life of up to 30,000 hours. Other features suitable for robotics include high sensitivity due to low compliance and fast approach to the end position.
The drive flange is designed as a hollow shaft and can be designed according to customer requirements. Depending on the size, the precision gearboxes are available with reduction ratios from 50 to 150.

Expanding the radius of action

The trend in the industry is towards complete automation of assembly, handling, testing and machining processes. In future, these activities will increasingly be carried out by lightweight robots and cobots. However, their range of movement is usually limited due to their size. Linear system axes act as range extenders to extend the action radius and reach of robots.

Cobot with linear axis for range extension. The compact, ready-to-install linear axis consists of the MDKUVE tandem module, a matching motor/gear unit, preassembled motor cables, a drag chain for all supply lines of the cobot and motor controller.

© Schaeffler

Schaeffler is launching a complete, ready-to-install solution for these applications. The horizontal linear axis consists of the MDKUVE tandem module, a suitable motor/gear unit, preassembled motor cables, a drag chain for all supply lines of the cobot and the motor controller.
Longer linear axes are designed as multi-part linear modules. The linear axis systems can be connected to the controller via the Profibus, Profinet or Ethercat interfaces.

The tandem version consists of two parallel profile rail guides (recirculating ball bearing and guideway assemblies). Depending on requirements, the user can choose between a toothed belt and a ball screw drive. The triple toothed belt drive enables range extenders with a length of up to 18 m, travel speeds of up to 5 m/s and a repeat accuracy of ±0.1 mm. Tandem modules with ball screw drive are suitable for lengths of up to 6 m. Speeds of up to 1.7 m/s and a repeat accuracy of ±0.025 mm can be achieved.