FEATURE GEARS & GEARBOXES U
sing different numbers of gear teeth, gear stages that allow
flexible combinations, and varying the number of planetary gears, are ways in which gearbox manufacturers can provide modular product portfolios. Depending on the gearbox configuration and the associated requirements in terms of rigidity and load carrying capacity, bearings with different dimensions must then be implemented in a single bearing position, which requires a wide variety of housings, housing covers, gears and shafts. Schaffler has, however, developed a
new concept in which bearings of different designs but with identical dimensions can be implemented in one bearing position for various gearbox configurations. These ‘interchangeable gearbox bearing
solutions’ will be available based on dimension series 18 for high precision servo planetary gearboxes. As an example, FAG deep groove ball bearings from series 618, INA angular contact ball bearings from series 718, and INA SGL angular contact roller bearings, allow the bearing support’s load carrying capacity, speed range and rigidity to be adjusted while retaining the same design envelope. Of the three variants, the INA SGL angular contact roller bearings offer the highest level of rigidity, which allows extremely rigid bearings and drives with very high positional accuracy to be achieved. According to Schaeffler, not only do
identical outside dimensions eliminate the need for special adapters and component variations, particularly for the shafts, housings and housing covers, but the associated development steps such as drawing modifications and NC programming in the manufacturing process, are no longer required. The reduction of gear, shaft and housing variants means higher production volumes, lower unit costs and faster deliveries.
PLANETARY GEAR BEARINGS The design envelope and rigidity requirements of planetary gears means they are often supported by cylindrical rolling bearings without an outer ring. Both full-complement designs and designs with cages are used here, depending on the required load carrying capacity and speed, but these bearings are not interchangeable because their envelope circle diameters are different. As a result, new planetary gears must be designed, produced and mounted. To make interchangeable bearing solutions available, even for planetary gear bearing
50 JUNE 2019 | DESIGN SOLUTIONS
CHANGING THE FACE of gearbox development
At this year’s Hannover fair, Schaeffler not only announced that it is helping gearbox manufacturers reduce the number of different parts used, thanks to interchangeable
gearbox bearing solutions that meet different requirements in the same design envelope; but that it is digitalising gearbox design through the creation of digital twins
Above: The REXS interface is freeware, and is available at
www.rexs.info
supports, Schaeffler’s design engineers have developed the INA RSLK1822, RSLK1830, and RSLK1850 cylindrical rolling bearings with cages based on the dimensions of full-complement RSL bearings. These feature identical outside dimensions and so can be used as replacements without any structural changes or design adjustments.
DIGITALISING DESIGN While there are a number of specialised software and CAE
tools available for designing and simulating gearboxes,
The objective of Schaeffler’s new concept is to allow bearings of different designs but with identical dimensions to be implemented in one (i.e. the same) bearing position for various gearbox configurations
manufacturers and their suppliers still often exchange gearbox data manually. So, in collaboration with
SEW-EURODRIVE and the FVA (Research Association for Power Transmission Engineering), Schaeffler has developed an electronic data transmission system that replaces this manual exchange and eliminates repeated gearbox modelling processes by means of a standardised interface for gearbox data. As a result of this, development times
are significantly shortened and a basis is created for the generation of digital twins that can be used, for example, to analyse operating data as part of Industry 4.0 solutions. Known as REXS (Reusable Engineering
Exchange Standard), version 1.1 offers a standardised modelling system and nomenclature for any desired gearbox with spur gear, bevel gear and planetary
gear stages, as well as their components. REXS is currently integrated into the FVA Workbench from version 5.0 upwards, into all current versions of Schaeffler’s Bearinx rolling bearing analysis tool, and into the SEW-EURODRIVE WESILAB gearbox calculation program. Even commercial CAE tool suppliers have now implemented the REXS interface or are planning to introduce it as part of their next releases. A simple mouse click is all it takes to generate a REXS file from the gearbox models. Schaeffler now offers the automatic
exchange of gearbox data via the REXS interface. Customers can obtain calculation results from Bearinx significantly faster, which speeds up their development processes.
DIGITAL DATA EXCHANGE According to Schaeffler, gearbox manufacturers with a high proportion of customer-specific application development will benefit greatly from being able to digitally exchange data with their suppliers. Dr. Heinrich Bolz, head of
calculation and simulation in gear unit development for SEW-EURODRIVE, commented: “With REXS, gearbox data can be transferred quickly and without errors, which means the interface makes an essential contribution to the optimisation of our innovation process.”
Schaeffler
www.schaeffler.co.uk
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