How can a manual translation stage be motorized?
The movement of Thorlabs' manual translation stages is driven by a micrometer or other adjuster, which can be replaced with a motorized actuator that has a compatible travel range and barrel diameter. Before making the substitution, it is important to fully retract the installed adjuster to protect the stage from the mechanical shock of a sudden release of spring energy.
Video Clip 1: It is important to completely retract the installed micrometer or other adjuster as the first step. If the adjuster is extended when it is released from the stage, the top plate of the stage will be propelled backwards into a hard stop. The mechanical shock may damage the stage.
Video Clip 3: After the micrometer on the XR25P stage is completely retracted, the locking cap screw on the stage's barrel clamp can be loosened with a 5/64" (2 mm) hex key and the adjuster removed. The barrel of the motorized actuator, which is the DC-servo-motor-driven Z825B in this example, is then inserted and the locking setscrew is tightened until snug.
Video Clip 2: After the adjustment screw on the MT1B stage is completely retracted, the locking cap screw on the stage's barrel clamp can be loosened with a 3/32" hex key and the adjuster removed. The barrel of the motorized actuator, which is the stepper-motor-driven ZFS13B in this example, is then inserted and the locking setscrew is tightened until snug.
Check Barrel Diameter and Travel Range Compatibility
These stages secure the actuator using a barrel clamp, which makes it necessary to match the actuator's barrel diameter to the clamp's specifications. Both stages chosen for this demonstration accept actuators with a 3/8" (9.5 mm) diameter barrel.
The travel range of the actuator must not exceed that of the stage. An actuator with a larger travel range can potentially force the stage to extend beyond its limit, which may damage both the stage and the actuator's motor. An actuator with a shorter travel range will cause no mechanical harm to itself or the stage, but the stage's travel range will be reduced. The MT1B and XR25P linear translation stages included in this demonstration have travel ranges of 0.5" and 1" (13 mm and 25 mm), respectively.
Retract the Adjuster to Avoid Damaging the Stage
Fully retracting the installed adjuster, before doing anything else, avoids a significant cause of damage to these stages. When the adjuster is fully retracted, the top plate is positioned as far backwards as possible to relieve the spring tension. Ideally, the tip of the adjuster would no longer be in contact with the stage.
An extended position is dangerous due to the force exerted by the stage's internal springs. The spring force keeps the top plate, or moving world, in contact with the tip of the adjuster (Clip 1). If the adjuster is extended when it is released from the stage, the spring force on the top plate will propel it backwards into a hard stop. The mechanical shock of this collision can be severe and potentially misalign the stage's components, affect the ball bearings, and introduce angular deviations to the stage's travel.
Make the Replacement
With the installed adjuster completely retracted, the locking cap screw in the barrel clamp of the MT1B or XR25P stage can be loosened using a 3/32" or 5/64" (2 mm) hex key, respectively. This will release the holding force on the barrel of the adjuster, so that it can be removed (Clips 2 and 3).
Insert the barrel of the motorized actuator and tighten the locking cap screw until it is snug, but not too tight. The spring load on the top plate should not be able to push the actuator out of the barrel clamp, but the locking screw should not be so tight that it deforms the barrel, which could affect the linearity of the actuator.
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