With its brushless direct-drive motor, integral precision encoder and an air bearing design combining high stiffness with exceptionally low axial, radial and tilt error motion, Aerotech's new ABRS series rotary stage is claimed to represent the ultimate in high-precision angular positioning with the added advantage of a very low vertical profile to combat stack-height-related errors in multi-axis positioning systems.
The new series is available in four sizes with nominal, square dimensions (width x depth) of 150, 200, 250 and 300mm.
Tabletops have diameters of approximately 20mm less than the width and each model includes a 360-degree reference scale.
The maximum positioning resolution on the largest stage is 0.036 arc-sec with speeds up to 500 rpm.
Aimed at demanding high-throughput production and inspection applications, including semiconductor manufacture, optical metrology and nanotechnology device fabrication, the new range combines ultra-smooth and precise angular motion with extreme positioning stability and has further benefits of a very long life with virtually zero maintenance.
For such high-precision applications, face error motion (the combination of axial and radial bearing errors resulting in a tilt angle of the rotating table top) is of fundamental importance.
Aerotech's specification for asynchronous tilt error is less than 0.08 arc-sec for the smallest model and below 0.04 arc-sec for the largest model. This is measured to ANSI/ASME standard B89.3.4m using the Donaldson ball reversal method for axes of rotation using both synchronous and asynchronous methods.
Aerotech's own air bearing design with active preload brings together precision and stiffness to ensure that tilt error and planar performance are unrivalled for commercially available products, with all other specifications being equally impressive.
However, the ABRS rotary stage precision does not compromise its load carrying or speed performance specifications - with maximum axial loads up to 950N (500N radial load), the largest stage produces more than 30Nm of peak torque and is capable of speeds in excess of 8rev/sec thanks to Aerotech's S series brushless and slotless direct-drive motors that produce high torque with minimal heating.
The slotless S series motors are cog- and torque-ripple-free and, with zero-backlash and exceptionally smooth velocity and torque control, the motor is excellent for scanning at low or high speeds or for highly stable positioning with very fast settling times.
All these factors combine to ensure that production throughput is maximised and the completely non-contact design ensures a very long working life with minimal maintenance.
As standard, a sine-wave output encoder allows a fundamental angular resolution of 3600lines/rev on the smallest stage and 18000lines/rev on the largest 300mm wide unit. A square-wave output encoder option is also available and the final resolution on the largest model is 0.036 arc-sec with the A3200 Automation Platform controller with maximum multiplication and quadrature.
To ensure minimal stack-height related errors in multi axis positioning applications (caused by the effect of individual angular pitch, yaw and roll errors that culminate in a compound error at the point of measurement or reference), the ABRS has been designed with an extremely low height for an air bearing design. With overall height dimensions of only 80, 90, 100 and 110mm, each model also includes a clear aperture for product feed-through, laser beam delivery or for general clearance. Construction material is aluminium, with a hard-coat (Rockwell 62) finish for maximum durability and each model is generously equipped with threaded and counter-bored mounting holes on the tabletop and main body.
As with all Aerotech products, custom engineered modifications can include different mounting configurations or complete application specific re-design. Rate table and inertial guidance test-stand variants for the ABRS range are available on request from Aerotech.
For more information, visit www.aerotech.co.uk
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