The Z-stage for the Ultimaker 3D printer is made up of layered pieces of plywood that clamp around LMU12LUU linear bearings. That construction results in an unstable Z-stage, either due to movement of the bearings in their seats, or movement due to moisture content levels in the wood itself.
This design does away with the LMU12LUU bearings and replaces them with LMK12LUU bearings that offer a flange to attach the (perpendicular) platform. Furthermore, the plywood is replaced by 10mm acrylic, to avoid warping due to changes in moisture content.
It has 4 tapped holes to mount the regular Ultimaker built platform (10mm acrylic).
This is very much a work in progress, as I have not made one yet!
This thing is shared with a CC-BY-SA license with a special exception, see license.txt for details.
2 LMK12LUU linear bearings. this is the double-long version, 60mm tall, capped by a square flange at the end. A rounded or flat-rounded flange variant may also work, you may need to modify the mounting holes for these.
3 printed parts: the nut-holder, the compensating slide and the slide pin. Print these with as much precision as you can: too much roughness on them will prevent XY movement of the leadscrew nut, leading to small disturbances in the Z direction ('Z wobble).
Mill out the platform part out of Suitably thick Acrylic, Trespa or any other suitably stiff material. Drill all holes with 2.5mm drill and tap with a M3 tap. Assemble and mount in your Ultimaker. You may need to defer tightening the bolts attaching the bearings, to allow them to absorb small size variations.