I was thinking of designing a smaller version of the MPCNC and I have several hardened ground rods 3/8" leftover from another project. That project used oiled brass bushings.
I started looking around and learned about Igus bearings in a video by Thomas Sanlanderer on YouTube
In the comments Reforged Criterion talked about having great luck spinning PLA bushings for a few seconds until the got hot. Once cooled they were a perfect fit.
So I started thinking. Can I actually replace each of those sets of three bearings with a single hole?
Also in the comments Antonie Kriek mentioned heating up the rod and letting the PLA melt just a bit around it.
On the corners you could just print columns with two holes at right angles.
Maybe we could align the rods by pressing them to a surface plate and heat them a bit until the alignment was perfect.
I don’t known what would happen with conduit but I imagine one could actually grind it very smooth with a jig and an angle grinder.
Could the pieces be so much simpler that they could just be cut out of plastic stock?
Igus bearings loose tolerances over time. For a 3d printer, it takes longer, but for us, it would start to get too wonky within a year, maybe less if you’re really running the machine every day like Ryan.
Could you print two concentric hollow cones one inside the other. The inside and outside would be a cylinder. One would get bigger the other smaller. Make them out of PLA. As things got worn a spring or a screw could push the cones together.
The quality of rail that would take to work for long is far too expensive for anyone that does not already have some. Even then I have not done any research on the loading they are designed for.
Your design is very tolerant of imperfections in the pipes. Do you have any idea how much of the total system error is caused by the imprecision of electrical conduit?
In a jungle in Guatemala I once ground 1" thick 18" dia. disk of metal to within a couple thousanths of an inch of perfectly flat and parallel with an old sanding belt glued to a piece of plywood, an angle grinder and a sharpie. (That is actually true but that is another topic).
I wonder if you took two pieces of wood and put something like chalk of two different color on them and rubbed them together. Then sanded down the spots that rubbed color off and repeated this. Like scraping ways or making a surface plate but out of wood became it would weigh less and be faster. When you have them flat (at least until the humidity changes) glue sandpaper to both on them. Now put three pieces of pipe between them and roll them back and forth or maybe in a swirling motion. After a number of rolls take one piece out and put in a fresh one. I wonder how close you could get the pipe to straight and round?
If the plastic pieces that ride on the pipes just had metal plates on the ends with a piece of threaded rod running through, nuts on the outsides could easily squeeze the PLA. Heat it if you have to.
Maybe this won’t work. But thanks for letting me think it through on your forum.