High speed spindle bearings in X-life quality

At EMO 2017, Schaeffler presented an entire range of new, high-speed spindle bearings in premium X-life quality. These FAG spindle bearings allow machine tool manufacturers to further increase the performance of their motor spindles in terms of mechanical and thermal load carrying capacity, thus offering their customers a boost to productivity and competitiveness.

Three fundamental designs of spindle bearing have established themselves on the market, which can be categorised by the size of the rolling elements: large-ball series, small-ball series, and designs with medium-size balls.

With its new M, HCM and VCM series of premium X-life High-Speed spindle bearings, Schaeffler has combined the kinematic suitability for high speeds of its existing small-ball high-speed series with the robustness and load carrying capacity of large-ball bearings. This was achieved by matching the ball size, osculation and radial internal clearance together in a targeted manner. 

Important development objectives for the X-life High-Speed series also included an internal design with optimised friction behaviour and a high tolerance to rapidly changing thermal operating conditions, such as those that frequently occur in motor spindles. This optimised design greatly reduces the rise in bearing preload caused by influencing factors such as interference between the bore and the bearing, high speeds, and large temperature gradients between the shaft and housing. 

The increase in preload is only desirable within certain limits, because parameters such as friction and heat generation in the rolling contacts also dramatically increase at the same time, which limits the maximum permissible speed.

The new FAG spindle bearing series will be offered in three different versions.

“M” version: cost-effective and robust

The balls and rings of M-series X-life High-Speed spindle bearings are manufactured from the proven 100Cr6 rolling bearing steel. This version provides a high-performance, cost-effective bearing solution for motor spindles.

“HCM” version: outstanding productivity due to high performance and suitability for high speeds

HCM-type X-life High-Speed spindle bearings are equipped with ceramic balls and rings made from 100Cr6 rolling bearing steel. Due to their high-performance capability and suitability for very high speeds, HCM spindle bearings allow the performance of motor spindles to be increased even further.

“VCM” version: new degrees of freedom in motor spindle design

Spindle bearings in the VCM X-life High-Speed series also feature balls made from ceramic material, but with bearing rings made from the newly developed Vacrodur high-performance material. This steel is characterised by its extremely high load carrying capacity, wear resistance, and very high-temperature resistance – particularly in the case of abnormal lubrication conditions such as insufficient lubrication or contamination. VCM-type spindle bearings open up entirely new levels of freedom when designing motor spindles compared to conventional spindle bearings.

Bearing configurations for every application

The M, HCM, and VCM series of X-life High-Speed spindle bearings are available for dimension series 70 and 719 and with nominal contact angles of 17 and 25 degrees. Furthermore, three different pretension options are also available. As is the standard practice for spindle bearings, these bearings are delivered with universal adjustment, which means that any desired arrangement of individual bearings and sets is possible. The spindle bearings can be designed in both open and sealed versions, as well as a “direct lube” version with lubrication holes and seals in the outer ring. Available bore diameters range from 25mm to 130 mm, and 50mm to 80 mm will initially be available for sealed versions. Further diameter ranges are also planned in subsequent releases.

With the new X-life High-Speed spindle bearings, spindle manufacturers can significantly increase the mechanical and thermal load carrying capacity of their existing product series without changes to the design. The new series opens up entirely new levels of design freedom thanks to its high-performance VCM version.