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High-performance bearings for automation technology and robotics MACHINE ELEMENTS Bearing supports in robotics and precision gearbox manufacturing share the same need for high load carrying capacities and high rigidity in minimal design envelopes. Cylinder roller-based bearings provide the solution. The angular contact ball bearings from ISO series 718 are used specifically in the output side of high-precision planetary gearboxes in order to significantly reduce the design envelope required. At the same time, however, these bearings also have to transfer high combined loads that are made up of axial and radial forces together with tilting moments. They are also a component used in robot hand axes, where the focus is on the low weight of the overall construction and the large hollow shaft, which can only be implemented with very small bearing cross-sections. The deformations and displacements to which the angular contact ball bearings are subjected as a result of these forces and moments are the biggest limiting factors on the path towards even greater precision. Line contact offers better tilting rigidity and less deflection Schaeffler offers a technologically and economically attractive solution for increasing rigidity and load carrying capacity in an identical design envelope with its INA angular contact roller bearings. These are rolling bearings with cylindrical rollers and raceways that are arranged at an angle to the bearing axis. The line contact of the cylindrical rollers ensures an outstandingly high level of rigidity, a noticeably high load carrying capacity and minimal deflections. A simple comparison demonstrates this clearly: A ball with a diameter of 10 mm that is supporting a nominal force of 1000 N causes a deflection of 40 µm, while a cylindrical roller of the same diameter reduces the deflection to 8 µm and thereby offers a 5-fold increase in rigidity. SGL series – precise and rigid The angular contact roller bearings from Schaeffler, are available in 2 designs: SGL and AXS. The precisely ground, triangular ring cross-sections of the SGL bearings together with the linear contact of the cylindrical rollers allow very precise, rigid bearing supports with a high load carrying capacity to be achieved. The cage, which is made from wear-resistant plastic, is located between the bear- WORLD OF INDUSTRIESMOTION, DRIVE & AUTOMATION 5/2017

ing rings and is guided by the shaft. Bearings from the SGL series correspond to dimension series 18 and can thus be used as a 1-to- 1 replacement for angular contact ball bearings from series 718. In comparison to the 718 series, SGL series of the same size allows the tilting rigidity of entire bearing supports to be increased from 50 to 230% on the output side of planetary gearboxes, depending on the size. The company Wittenstein alpha was among the pioneers in the use of this rolling bearing type, which it generally uses in its TP+ high-performance gearboxes. Dipl.-Ing. Marc Mahler is a design engineer at Wittenstein alpha and provided an explanation on the project: “When we were in the process of developing our TP+ gearboxes from the existing TP series, we defined 6 ambitious targets that we then set about tackling with Schaeffler: To reduce the gearbox’s design envelope, increase the output side bearing support’s load carrying capacity, increase the rating life, improve the tilting rigidity of the output side, to achieve multiple usage, and optimize costs.” The engineers from Schaeffler developed several bearing concepts based on this requirement profile – and the analysis they carried out led to the development of the SGL angular contact roller bearings. Marc Mahler adds: “From a gearbox manufacturing perspective, the SGL bearings are very compact, rigid, and high-precision bearings that can transfer large loads.” AXS series – rigid and lightweight „The O arrangement of the bearings allows large distances between support points and very rigid bearing supports to be achieved.“ A key characteristic of the AXS series bearings are the rings, which are manufactured using forming methods and are just 1 mm thick. Because these rings have no intrinsic geometrical stability, they can therefore perfectly adjust to the conical bearing seats in the adjacent construction. As a result, the AXS bearing support is decisively dependent on the quality of the adjacent construction – particularly on the roundness and surface quality of the shaft and housing as well as the angular tolerance. Surfaces that are turned or precision turned in a clamping operation are sufficient in the majority of applications. The bearing rings can also be combined with constructions made from aluminum or other lightweight materials, which allows extremely lightweight constructions to be created. Because the 2 bearing rings are identical, there is no risk of parts being confused during the mounting process. The inner ring is centered on 01 INA bearings type SGL fit into the same design envelope as the 718 series of angular contact ball bearings but have a very rigid roller contact 02 Wittenstein alpha’s TP+ planetary gearboxes with SGL angular contact roller bearings allow bearing supports with particularly high tilting rigidity, high load carrying capacity, and low space requirements WORLD OF INDUSTRIESMOTION, DRIVE & AUTOMATION 5/2017