The recent EMO 2017 exhibition in Hanover, Germany provided a platform for NSK to showcase a number of innovations for the machine tool market. Principal among them was the ROBUST series of angular contact ball bearings, which features NSK’s new SURSAVE cages that have been developed specifically to match the application profile of main spindle drives. ROBUST bearings with SURSAVE cages create the condition for spindles to achieve high rotational accuracy, thus facilitating high-precision machining even at very high speeds.
SURSAVE cages that have been designed specifically for the main spindle drives of machine tools.
When performing high-speed machining, temperatures in the spindle bearing assemblies can easily escalate. NSK’s ROBUST series has been designed to counter these effects, reducing heat build-up to a minimum. In turn, this helps increase the reliability of the machining process at high speeds.
ROBUST angular contact ball bearings are proven under high-speed conditions and are already being employed by numerous machine tool and spindle manufacturers. The bearings are available in different versions, including with steel and ceramic balls, raceways made of various special steels, and with several cage types. By specifying the new SURSAVE cage, heat accumulation will be reduced even further. This effect is thanks largely to the very low frictional torque produced by SURSAVE, which is some 20% less than that witnessed in conventional angular contact ball bearing cages.
An increasingly important measure of performance is NRRO (non-repeatable run-out) of the main spindle. In short, low NRRO improves the surface quality of machined parts. Using ROBUST SURSAVE bearings, NRRO can be halved. Moreover, this is achieved despite offering a speed factor (n x dm) of over 3 million, which represents an increase of 20% compared with traditional angular contact ball bearings.
The sum of these characteristics – high speed, low frictional torque and very high rotational accuracy – means that spindle drives fitted with ROBUST SURSAVE angular contact ball bearings produce consistently precise parts in shorter cycle times. Manufacturers producing components such as gear wheels and other drive components, as well as dies, will all benefit.