Failure, Confusion and Success  

Failure, Confusion and Success

I would like to add my first few days of MMU2 experience in the hopes that it saves someone from the dumb mistakes I made during mine.

I built, installed, and calibrated the MMU no problems. Yay! I figured that everything would be perfect from here on since I had a perfect experience with the MK3 build. I was wrong, but not for the reasons you may think.

I had 3 rolls of PETG and only one of PLA so i figured PETG was the way to go to test the MMU. I have been getting perfect prints with PETG. All the sample GCODES are generated for PLA so I figured I would just slice them with slic3r. That process seemed to go fine.

When i finally went to print, the filament would load, print perfectly up to the first layer change, and then strip in the MMU during extract/unload causing a blob to form in the extruder that required surgery to remove. Time after time after time I adjusted screws, checked tube resistance, calibrated bowden tubes, poked around on the forum, ate gummy bears, cleared jams, and otherwise fiddled about. No changes, 100% failure for every filament change.

Then I started really reading the Forum instead of pretending to read it(!) and noticed that many people said print the examples first, no changes. when that works move on. So I loaded the sheep gcode and even though the code is for PLA i ran it anyway, filament jams are gone, and the MK3 s happily printing! Printing problems did happen due to to the PLA/PETG mismatch but I adjusted the temps on the fly and things looked great.

So now I am wondering why my GCODE fails and the examples work. Turns out that in Slicer I created my own configuration settings one day by taking the regular MK3 configuration, enabling multiple extruders, and then saving as the MMU version. Sounds harmless since my MK3 was printing perfectly, right? Wrong! Apparently there are many more changes in there that I didnt know I needed. I mention this in the hopes that I save someone else from doing the same thing.

Anyway, once I ran the configuration wizard, generated the real configuration settings for the MMU2 and resliced with my material settings things magically started working. I still have an occasion filament load error, and the firmware interface is a little rough, but it has potential to be just as solid as the MK3 itself.

What are the lessons here? Not sure that has a simple answer. I thought I knew what I was doing, and had lots of experience with the printer and Slicer, but obviously did not when it came to the MMU2. I wish there was clearer documentation on what each config setting did relative to the MK3, and what changing them does. It still seems a little trial and error is in order, which I am fine with, and actually enjoy as long as eventually win.

I want to specifically point out what I did NOT do during the whole process. I did not go online and post messages saying that the equipment is junk, and doesn't work, and why would someone build and sell such a thing. Maybe that is due to 35 years of engineering experience, or maybe it is just who I am. Prusa has created what I believe is the best 3d printer for the money on the market today.

Keep poking at the problem, change one variable at a time, be open to others suggestions, and keep learning.

Happy printing