This a 100% printable Z stage bearing replacement upgrade.
It seemed that no matter how carefully I aligned the Z stage bearings - that when assembled into the Thing-O -Matic, the Z stage would chatter when lowering. In addition, there was some binding happening on the upward direction as well causing the Z axis to miss steps.
The result of Z steps missed is apparent in the last picture. That piece worked well enough to fix the problem but a replacement was soon printed. Once it served it's purpose I stress tested it. It was surprisingly strong, taking far more effort to break than I expected. The parts are easily strong enough to support the Z stage, by far.
Another symptom of missed Z steps is the extruder skipping steps or stripping filament. If the Z axis fails to rise for the next layer then the nozzle will be too low and it is harder to push the filament out - resulting in filament stripping or the extruder skipping steps.
It was clear that the Z stage needed an upgrade but I really did not want to have to order bearings or search hardware stores for the right size brass tube, nor did I want to alter the machine in such a way that was not reversible. Using plastic for the bearing surface may not seem to be a precision thing to do but as it turns out this has been highly reliable, repeatable and silky smooth. It is also designed in such a way that the bottom bearing surfaces contact the front of the rods and the top bearing surfaces contact the rear. This means that you can lift (tilt) the Z stage by about 10mm. This can be a useful feature when the nozzle accidentally crashes into a bolt head.
This may not work with an ABP due to clearance issues.
I designed this so that no modifications to the TOM are required. You only need to remove the original bearings and bolt in place. If you want to re-use the same bolts to attach the bottom pieces you will need to first draw the nuts down a bit further into the wood by over-tightening slightly. Otherwise, just use longer bolts.
Printed with .28mm layer height, 3 shells and 35% infill ( I think).
Use a cotton swab to put a small amount of lithium grease in where the rods contact the plastic.
Enjoy silky smooth and silent Z stage movement!