Rules of Thumb
- For high speed, vertical applications, the linear motor driven positioning stage may be the only choice, although they are not ideal for vertical applications because when power fails the table of the stage will move downward unless a fail safe brake is incorporated into the stage.
- Constant force springs, counterbalancing with an equal mass, or a ported pneumatic cylinder can be used to negate the force of gravity on the payload and thus dramatically reduce the force required to hold the payload in a static condition. Otherwise the linear motor always has to generate sufficient force to over come the force of gravity when the stage is stationary. These methods will not work when accelerations exceed 1 g.
- The ball screw driven positioning stage is usually the preferred method for slow speed, heavy payload, vertical applications.
- Velocity- 240 inches / sec [6 m/sec] is typically the maximum velocity which is limited by the bearings, motor back emf, DC bus voltage of the amplifier, and velocity limits of the encoder.
- Acceleration – 10 g’s is typically the maximum, which is limited by the bearings, encoder and the motor.
- Accuracy - .000040” [1 micron] is typically the best accuracy that can be achieved and is limited by the servo system, the encoder and environmental conditions.
- Repeatability - .000020” [0.5 micron] is typically the best repeatability that can be achieved and is limited by the servo system, the encoder and environmental conditions
- Force – 1660 lbs [7380 N] is the highest force from a single coil assembly but additional coil assemblies can be mounted in series or parallel to increase this number.
- Travel – the maximum travel is 160” [4 m] because of machining limitations on the base and linear rail lengths. For special applications, piecing together stage components can increase the maximum travel.
- The stage must be mounted to a flat, and stable base structure using the available mounting holes in the base. The screws used to mount the base must be torqued in to place.
- The payload is mounted to the moving table of the stage using the provided threaded mounting holes. Any cables and hoses from the payload can be routed thru the existing cable carrier. Payload power cables must be twisted and shielded in order to reduce noise.
- The base of the stage must be properly grounded
- Periodic maintenance of the stage is required to ensure trouble free operation. The bearing guide blocks should be lubricated every 3-6 months depending on use and environmental conditions.
- For stages with open optical encoders, the scale should be occasionally cleaned to remove dust.