Posted to News on 12th Oct 2006, 16:52
Combined radial/thrust bearing incorporates angle measurement
RA Rodriguez is introducing Unitec's high-precision combined radial/thrust bearing for machine tool rotary tables and spindle heads that features an integrated angle measuring system. Available in the UK through RA Rodriguez, the Unitec RTB AMS bearings use an inductive detecting principle. As a result, the measurement accuracy is not influenced by magnetic fields, and lubricating fluids and greases do not pose a problem. The system is therefore claimed to be more accurate than others currently available.
Unitec's system includes a graduated stainless steel scale that fits precisely onto the bearing's washer ring and two sensor heads on the outer ring, sited at 180 degrees to the centreline. During rotation, the sensors detect the slots on the scale and generate a 1Vpp output signal that is sent to the machine's CNC, enabling the angle to be continuously monitored. The scale slots – set at intervals of 1mm – are protected from dirt ingress by a metal cover.
This new bearing is available in seven sizes with bores from 150mm to 460mm. One reference point is provided as standard but, on request, several distance-coded reference marks can be specified at any angle from 40 to 15degrees, depending on bearing size. The absolute position may be determined by detecting, during rotation, the single reference point or, alternatively, two distance-coded marks.
Output signals are 1Vpp (for terminal resistance of 120ohms) with optional TTL square wave on request. Total accuracy of the system is up to +/-3arc-sec (460mm bore size). With a few exceptions, these new angle measuring bearings are interchangeable with the majority of the Unitec RTB range, as well as some competitor systems.
