How about something like this for the z stage? 

How about something like this for the z stage?
https://www.youtube.com/watch?v=vXZSMdeQVG0

Well, after you add guide rods to stabilize it, it’s not less complex. Worse, Z steps / mm is not longer constant. Even with firmware or postprocessor support for the nonlinear axis, you’d get Z banding artifacts that look like a diffraction pattern.

It would be smoother if the coupler was bored straight, even if that was true it doesn’t look linear in its movements. Moves slower at the top faster at the bottom.

Movement along the axis of the screw is amplified when moving the ‘scissor’ part of this contraption;

Any backlash in the nut will also be amplified… And there is also (albeit minor) play in every joint of the scissor action mechanism.

I think, if you’re going to have a motor, and you’re going to have a screw, might as well have a screw-driven Z, you only add more components and more points which can introduce error with a scissor design.

It would certainly look cool tho :slight_smile:

I have been working on a box-format lab jack like the Newport 271, only built using 3D printed panels linked using thin brass nails.

I am currently scaling the adjustment using M3x20mm screws passing through a captive M3 nut on the near side and deflecting the opposite side by pushing away a small metal cup (best so far is a partial (arc) of a M5-M6 flat washer, dimpled using a center punch).

Assembled, the side with the cup is first, then the captive nut assembly with a split nail adjoining the two sides, and finally the third box segment set at 90 degrees.

I am striving for a final scale of 1/4-3/4 inches (outer) to make fine adjustment easier. I was thinking of threading a hole in the base to allow an M4 anchor in the place of the usual jack screw.