The original vertical sliders were laser-cut MDF. The design worked well. One of my priorities was to replace them with custom printed parts. I ensured that the critical dimensions were exactly the same so that they would be a drop-in replacement. I re-used the same LM12UU linear bearings. Some of the improvements include printing a small lip around the top and bottom of the bearings so that they could not slide out, and the inclusion of a small recess for the endstop magnet to sit in.

Slider V3

Slider V3 installed