At EMO 2019 NSK presented its new Robustride cylindrical roller bearings for the spindle drives of high speed, high precision machine tools. These advanced bearings feature an optimised cage that facilitates more even lubricant distribution, which in turn reduces bearing wear, especially under high loads. Also launched at the show were NSK’s Robust angular contact ball bearings with improved accuracy class.
The spindle bearings of machine tools must meet very high requirements for running accuracy. NSK has developed various bearing types and series for this demanding application which are known as the Robust series. The series is now supplemented by the Robustride single-row cylindrical roller bearings. Robustride bearings offer a specially devised cage with geometry and guidance that have been improved specifically for this application profile.
NSK’s optimisation work included developing a way to better distribute the lubricant and, subsequently, create less and more uniform heat generation within the bearing. The lubricant flow in the bearing is directed in such a way that the inside (which is rather disadvantaged by centrifugal forces) is also supplied with lubricant in the optimum way. Any resulting surface losses are negligible and, even at the extraordinarily high speeds commonplace in many of today’s machining operations, very good lubricant distribution is achieved.
These design improvements serve to minimise bearing wear, especially at high loads. They also shorten the running-in period of the bearing grease. Another advantage is that Robustride bearings allow significantly greater tolerances in the bearing clearance due to optimised guidance of the rolling elements, which simplifies mounting procedures.
In addition, NSK has developed new cages for its series of Robust angular contact ball bearings. Since these bearings can also be found in many high-speed machine tool applications, they have been optimised to exhibit minimal frictional torque. As a result, less heat is generated during bearing operation (compared with other angular contact ball bearings), which as previously stated, also makes an important contribution to the reliability of the machining process, especially at very high speeds. Ultimately, machine tool spindles equipped with Robust Sursave angular contact ball bearings will impart very high surface quality on the components being machined.
In addition, Robust angular contact ball bearings are now available in accuracy class P3W. As a result of this development, the width tolerance of the bearings reduces from 250 μm previously, to 100 μm, which aids installation.
In Hannover, NSK also showed its Verify app for high-precision bearings. The Verify app enables bearings to be identified using the QR code on the packaging. This data – which includes individual identification number, measurement results from final inspection, dimensional tolerances and grease type – can be exported in standard formats and transferred to the customer’s in-house systems. The app therefore creates the prerequisite for the traceability of products in IT-based information and management systems.
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