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idler alignment issue?  

Chris Abbey
Eminent Member
idler alignment issue?

I've been pushing my printer pretty hard for the last few weeks... pretty much constantly printing something. These last few days I've been having lots of issues with the MMU either not extracting a filament all the way, or not being able to insert it. While baby sitting it last night (manually un/loading filament for every tool change) I noticed that I could feed filament through from the spool way too easy when it was supposedly engaged on the MMU2's pully. That got me looking and I realized that when the idler rotates around to "engage" a given filament... it was not lined up with the pulley! It was basically hanging in space above the entry where the filament goes into the block to then go into the selector.

I opened up the MMU before the next tool change and was very closely looking at the idler position as it stepped through the motions of trying to eject filament 1. After it failed and asked for help I forced the selector motor 3 "clicks" then pushed the retry button... then did one more click to get it where I thought it was supposed to be. Closed the lid and redid the "try again" button... BOOM worked perfectly. As did loading filament 3 that it was switching to. In fact, I watched it do 12 more tool changes flawlessly. Before this it had failed 100% of them for the past 40 or 50... and probably 50% of them for the 50 or so before that.

After that change, I kicked off a print that had 68 tool changes... it went flawlessly... I have another running now with 41 tool changes, I'm over half way through it, haven't had to manually interact once.

Is there a known case where the idler rotation gets "off" place? I would have thought that the initialization would have taken care of that... but I just realized I've not powered the printer down in probably 3 weeks or more. I'll give it a power cycle tonight after this print job finishes... but is there some way to force the idler to re-index with a gcode? or are we just supposed to reboot the printer periodically? I sure wish we could hit a button sequence on the MMU and get it to reset the idler while in the middle of a print... would be better than

And if you have issues with MMU2 either not getting filament ejected all the way, or not inserted all the way down to the extruder... maybe check that!

Posted : 07/02/2019 11:05 pm
Honorable Member
Re: idler alignment issue?

Agree! There should be a button to rehome the MMU idler at any time. It does have a distressing habit of sometimes getting a bit out of place, and rehoming can be done safely any time other than during a load/unload sequence.

Posted : 10/02/2019 6:04 pm
Craig Trader
Eminent Member
Re: idler alignment issue?

You may want to consider disassembling the MMU2 and checking the M3 screws that attach the idler to the stepper motor shaft. I did that and discovered that mine had loosened, causing the idler to drop out of alignment. Of course now that I've got it back together, I'm wishing I had used some Loctite Blue when I reassembled it. I guess I will the next time I have to tighten it.

I solve problems, usually with computers ......
Posted : 02/04/2019 12:35 pm