Hi all, I am trying to understand the limits of motion of the stage. What actually breaks or prevents excessive motion in the X and Y directions? For example if I keep driving in the +X direction what will happen? Will the stage flexures snap? the O-ring? Or will the motors just stall? How about the -X direction?
Is the general consensus we should get around +/-30,000 steps so around 3mm travel in each direction from the zero position?
I have been playing around with the stage manually turning the gears to try to understand exactly how it works but I’m still not sure. It seems the nut travels up and down on the bolt as it rotates and this pulls the inner part of the flexure up and down inside the leg and this pushes or pulls the stage. What exactly is the purpose of the O-rings?
Sorry if these questions are overly basic but I’m fascinated by the mechanism and I’d like to understand exactly how it works. Thanks 
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You are right on how the actuator column works. However in practice the screw can actually only pull the nut, it cannot push - the screw would just come out of the top. The O-ring pulls in the opposite direction, so turning one way the screw pulls the nut up, and the other way the screw lets the nut down under the pull from the O-ring.
The physical limit at the top is the actuator column hitting the top of the inside of the actuator housing. The physical limit at the bottom is the foot of the actuator column hitting the bridge in the middle of the foot. At the top the motors will stall, but they may also exert a twist on the column which could break it. At the bottom, the stage will stop and the O-ring will not be pulling any more. The actuator screw will screw out of the top of the actuator, the large gear will become loose and eventually I think the head of the screw hits the motor body. Playing with thecstage by hand is a good way of getting a feel for both of these. I just did it to check what I was writing!
For the number of steps we start with around 4000 steps per turn of the small gear. This gives 8000 steps for a turn of the large gear, which drives the nut 0.5mm per turn (M3 screw pitch is 0.5mm). The actuator is connected to the stage by levers, with a ratio of approximately 2 (less than 2). So we have about 8000+ steps per mm of stage travel. This is your understanding of 30,000 steps for 3mm.
The designed full range of travel is 6mm in each direction from the centre, so 12mm across.
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Wow thanks for that detailed reply. I just read through that while fiddling with the mechanism and I finally understand the physical stops. Much appreciated!
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