MMU1+2, first prints, good experience other than calibration  

MMU1+2, first prints, good experience other than calibration

Just thought I'd add my comments on a successful MMU2 build, particularly as I was working with the MMU1 + MMU1->2 kits, assembling for my MK3 (not an MK2.5). All went well, the MMU1->2 upgrade kit works fine on the MK3, and the original MMU1 steppers run fine with the MK3. (I never assembled the MMU1 so they've been sitting in the garage for quite a while.)

First prints were nearly flawless, and nothing went wrong related to MMU; the purge block for the sheep fell over half-way through, so she wound up being extra hairy. Pliers and gears came out perfectly (though I lost the bottom layer of one of the gears when I tried to get it off the sheet; too much PVA glue and too small to pop off with flexing).

No skipped layers!

I did add one mod at the very beginning, Newguy's suggestion of adding springs to the MMU2 outlet tube mount, being careful not to drive the screws in far enough to damage the probe. It consistently pushes out the plate as it is feeding filament into the extruder, despite manual calibration, so seems to be doing exactly what is intended.

Initial calibration was a complete mess however. I'm not sure how much of it was me learning how the thing works, and making sure I didn't have filament pushing through to the selector, but after attempting to calibrate a couple of channels it simply wasn't responding well, after rebooting it seemed to be failing to home, changing channels wasn't working, and calibrating the first channel seemed to be getting worse. I'm not sure which helped more, but I did a full firmware reset on the MMU2 and also opened it up to pull out, clean up, and realign all of the filament tips -- after that it got much better, and I completed the calibration on all channels without problem.

Oh, there was one actual printer problem: the short PTFE tube in the extruder top appears to have poor concentricity, and if a filament isn't very straight or curved in just the right way it can get stuck, and not load past to the bondtech gears. Since everything else looked OK I tried rotating the tube 180 degrees in place, and everything has fed perfectly since. This did complicate the calibration a bit since one channel repeatedly failed to make it through the extruder (with two different spools of PLA, odd that) -- once I tweaked the tube, that channel loaded and calibrated properly, and all was well.

I'm trying one other mod, the simpler spool feeder with a bit of tubing. I'm not convinced it's the best idea, since the retracted filament tends to curl up in random directions instead of always heading to the left, but it looks much less silly than the stock Prusa feeder arms. (Sorry, Prusa folks.) I'm going to try some additional tubing (1/4") as a sleeve over both tubing sections and see if I can keep it controlled that way.

Anyway, I wanted to post that the upgrade scenario works fine, and I've had a great first printing experience. Cheers!