This is an upgrade/alternative part for the Scalar S - 3D Printer (20x20x20cm). It replaces the bracket at attaches the x-axis track/rail to the z-axis lead screws. Specifically, it replaces the part named "ZWheelHolder_backFixed-_2020.stl" in the STL files.
The design currently calls for a hex nut to be slotted into an opening on the bracket, but I've had bad luck in the past where that slot has gotten worked out and widened over time and induced play in the assembly which would be particularly bad for a 3D printer. This design instead uses the M8 brass flanged nut that's pretty common in RepRap circles.
I've designed it so it can be used on either side, with the intention of the nut being attached to the side facing down and the protrusion on the nut facing up into the bracket (see the picture above.) Don't try to use a nut on both sides or you stand a good chance of binding and either jamming up your printer or shortening up the life of your z-axis steppers.
The Scalar S can be found here: http://www.thingiverse.com/thing:1973604
It's a great little printer. Admittedly, the documentation for this one is a bit lacking (versus the other size Scalar printers), but with pictures and the information they have on their site you can muddle through it without too many headaches. :-)
Monoprice Replicator 1 Clone
The resolution and infill are probably overkill, but this is what I generally use and the difference between 30% infill and 50% infill was a couple of grams and I didn't want to mess with it.