Schaeffler Group Industrial is presenting its new bearing-integrated YRTSM angle measuring system at the EMO 2007 trade fair. Due to its speed range and output signal properties, this system is suitable for use in highly dynamic and precise direct-drive rotary machine tool axes.

The measuring system is integrated into the high-speed YRTS rotary table bearing series which offers extremely high tilting rigidity and low friction. The resultant new YRTSM range is available with bore diameters from 200 mm up to 460 mm. Bearing limiting speeds and measuring limiting speeds of between 560 and 1,160 revolutions per minute can be achieved, depending on the bearing size. The output signal properties provided by the measuring system enable very rigid and highly dynamic drive control. Thanks to these characteristics, the new bearing/measuring system unit is particularly suitable for innovative rotary axes that are used both for milling and turning operations.

Integration of the angle measuring system into the bearing enables not only more compact designs but also a free bearing center that, for instance, permits the space-saving accommodation of supply lines. Moreover, auxiliary constructions for attaching the measuring system and measuring system alignment during installation are no longer required.

The magnetic dimensional scale, which is unsusceptible to contamination with greases, oils and emulsions, is metal-to-metal bonded to the rotating bearing shaft locating washer without resulting joints. Two sensor heads, offset by 180° and diametrically arranged relative to each other, undertake magnetoresistive, non-contact scanning of the washer. In this way, the system compensates for eccentricity caused by machining forces and achieves an absolute measuring accuracy better than +/-3 minutes of arc and a repeat accuracy better than 1“. Moreover, the procedure doubles the angular resolution that grows with increasing bearing diameter.

Both measuring heads are rigidly flanged to the rotary table structure. The rigid connection of the dimensional scale to the rotating rotary table and the robust, vibration-stable connection of the measuring heads to the basic structure enable supreme quality and rigidity of control. The plug connection at the measuring heads simplifies cabling, resulting in cost reductions in design, procurement and installation. The metal housing and seals protect the measuring head’s electronic system in particular against mechanical, chemical and electrical impact.

Advantages at a glance

-Especially suitable for machine tool rotary tables for combined milling and turning operations
-Measuring speeds of up to 1,160 rpm
-High amplification factors in control circuit possible
-Reduced requirement for installation space
-Free bearing center
-No additional components for measuring system attachment
-No alignment of measuring system
-High measuring accuracy
-Rigid mechanical connection to rotary table
-Non-susceptibility to contamination by greases, oils and emulsion

Courtesy of  FAG