Gearhead Gearheads are used between motor and drive screw; they improve position resolution and torque. Most models use preloaded gearheads to eliminate backlash. Leadscrews Leadscrews can provide very high resolutions and very smooth motion. A leadscrew drive consists of a motor-driven screw with a nut coupled to the moving platform of the stage. The nut can be spring-preloaded to reduce backlash.They have higher friction than recirculating ball screws so that they are self-locking; on the other hand, however, this has an effect on velocity, motor power and lifetime. Typical leadscrews have a pitch between 0.4 and 0.5 mm/revolution, up to 1 mm/revolution for longer travel ranges. Recirculating Ball Screws Recirculating ball screws have significantly less friction than leadscrews because they replace sliding friction with rolling friction. A recirculating ball screw drive consists of a motor-driven screw with a nut coupled to the moving platform of the stage. Balls in a closed circuit are located between nut (ball case) and drive screw. Backlash can be minimized by selecting the proper ball-to-thread-diameter ratio. Recirculating ball screws are not selflocking but very efficient and offer high velocities and long lifetime in continuous operation. PI uses pitches of 0.5, 1 or 2 mm/revolution. Threaded Spindle Drives Threaded spindle drives use rolls instead of balls as rolling bodies so that a higher load rating, higher velocity and considerably longer lifetime are achieved.

Linear Ball Bearing Recirculating Ball Bearings The balls run in a brass cage and are preloaded with regard to the hardened precision guiding shafts. Exact tolerances between guiding and bearing are necessary for zero backlash and low friction. Load capacity is limited. High-precision stages are equipped with precision double linear rails. Precision assembly allows these bearings to yield excellent results in terms of load capacity, lifetime, low maintenance and guiding accuracy. The moving part of the stages is supported by a total of four preloaded linear bearings with two rows of recirculating...

Magnetic Bearings Flexure Guides Magnetic levitation ensures excellent guiding accuracy in a plane, both linear and rotational: The passive platform levitates on a magnetic field and is actively guided by it. Sequence errors are measured and compensated by very accurate noncontact sensors. Contrary to air bearings, which are also very accurate, magnetic bearings can also be used in vacuum. The motion of a flexure joint is based on the elastic deformation of a solid. Therefore, there is no static, rolling or sliding friction. Flexure elements have a high stiffness and load capacity and are very...

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