MPCNC Bushing Edition 2

My other cnc (Lumenlabs based design0 using bushings is almost done now.

Taking the bushing idea farther I modeled another new design as a cross between the MPCNC and my Ultimaker clone printer.

I got a bunch of Mach3 boards in DHL somewhere, and a Aluminum foundry somewhere between China and my shop to experiment with new ideas, so figured I would re-visit this.

It is designed to accept both nema23 and nema17 motors without any re-design or re-print.

Brass bushing is 1 and 1/8 inch brass tubing that happens to be exactly 1 inch inside diameter. It is a tiny bit tight, so I used some 600 grit sandpaper to open up the bushing a little bit, then made a sort of adapter with a short section of the 1 inch pipe to mount to the drill with a m8 bolt. I then put polishing compound on the stainless tube and ran thru the center of the brass tubing bushings I cut 20mm long on the lathe.

I have not printed this pictured one yet. Still debating, carbon fiber or cast aluminum. I got a couple kilos of CF in the shop and the foundry soon to arrive. My CF filament prints so far have turned out very accurate dimensionally. Much better than my regular PLA. however the Alu is tempting me… lol

[attachment file=34228]

Any idea of what the rails are going to cost per foot?

Looks like a pretty cool design. Just curious, but did you consider a design using the Igus bearings that people are using as upgrades on the i3 rep rap and Original Prusa printers? Kinda curious why brass bushings instead of a dry coat production bearing? Bushings like you are going to use have been around for many years, so should be no question they will work and likely work well. Good luck on your project. Look forward to see how it works out.

The design seems ok, but… how will you tighten the carriage tube?
Seems to me that you have nothing to clamp it, so you need to have a crazy precision or to use temperature differentials to force it in and have it secured.

You might want to rework that part, otherwise you’ll have problems, unless you thought of something I cannot see on the pictures.

Also, If you go through the hassle of having precision tubes, I suggest you just go for linear bearings as I did on my machine. Price is similar to bushings and its, in my opinion, more forgiving in terms of tolerances and dust accumulation.

Last thing: having the bottom squared will take more time and more plastic if you plan to print it, you may want to round it instead. Won’t change much the rigidity.