[Solved] Printing seems to work, but......  

RE: Printing seems to work, but......

Do I get this right: Your MMU has no problems loading and unloading during multi material prints only if you cancel a print or select "unload filament" from the LCD menu you get an unsuccessful unload and have to manually remove the filament?

Do you use octoprint to cancel? (Octoprint uses M0 to cancel but your MK3 needs an additional M603 to properly unload and finish up)

Did you replace the PTFE in the hot end (the one below the bondtec gears in your extruder) with the one that came with the MMU when doing the upgrade? (the one supplied with the upgrade kit has a 1.85 inner diameter, the one originally installed in you hot end might have a different diameter)

RE: Printing seems to work, but......

Yes you do get that right. Exept the problem also is presenjt, after a first layer calibration. Basicly evertime the command comes from the Printer.I use the Printer to cancel.

But with unload manually, I actually mean: Pull out tue ptfe tube, cut the filament, let it retract into the MMU, Remove the Idler pull the Filament out via the void. EVERY FREAKING TIME....

I am not sure if I did recieve another PTFE tube, nore was there any insturction to do so....

It does Work now

So what did I do?

I honestly do not know. I had to loosten the screws so many times; i found that it works, best, when i turn the Screws with the springs, i Line up my hex with the Body of the Idler basically with this Line:

The Screw with Spring on the Extruder I do 2.5 full turns or 900°..

Why it worked with the Prints, but not with the load and unload on the Printer, I do not get it at all, but seems solved.
Hope this helps anyone.

RE: I've seen this before

I've seen it happen on a cancel or at the end of a single filament print when it doesn't do the ramming operation.

I've seen it happen for two reasons:

One is is fixed,  the idler bolt was too tight.  Support had me make sure the end of the bolt was flush with the surface right under the hex bolt.  This solved nearly all my mmu loading issues in one fell swoop.

Two is when the filament is overly wet and in need of running through the filament dryer.  you can tell, particularly with solubles or PLA that it becomes harder to push through the PTFE tubes.

I do however agree that a cancel doesn't appear to do the tip shaping as you would hope.  I'm hoping the rewrite of the mmu firmware that's currently underway will help.   I see MANY issues that come about from simply cancelling the print at the right time.  In particular if I forgot to select the right sheet profile and I realize it when it starts doing the leveling routine and I cancel the print... that gets the printer and the mmu out of sync nearly every time for me.

Idler tension / PTFEs

Sorry for not responding, I missed your answer…

I believe ssill2 is correct your MMU idler is to tight.  The screws have to be just below the flush position. At least they are on my MMU an it works nicely. 

What makes your problem mysterious is that you don‘t have problems during prints just when cancelling or manuell unloading.
Regarding the PTFEs: The one inside the extruder is very important for building the right tips during the ramming, obviously there are printers out there with 2 mm inner diameter PTFEs (you‘ll find comments about that in the comment section of the English online upgrade instructions for the mk3s to mmu2), that’s why the upgrade kit comes with 2 PTFEs with 1,85 inner diameter, unfortunately there is no explicit instruction to change them during upgrade. I recommend you check the spare bag of your upgrade kit….

Additionally: What solved basically all my loading/unloading issues was to change the PTFE between extruder and MMU and the PTFEs in the MMU (the 5 small ones) and the PTFEs leading to the MMU and replacing them with 2,5 mm inner diameter ones (a bit hard to get by but eventually I got a few meters from eBay).