Filament calibration for having good ending and avoid MMUS2 got stuck
 
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michele.b3
(@michele-b3)
Eminent Member
Filament calibration for having good ending and avoid MMUS2 got stuck

I am getting some issues to get the right temp to the filament since if it is wrong MMUS2 often gets stuck while changing color.

Is there any procedure to get better filament ending? I have worked already on "Number of cooling movements" and "Unloading speed at the start" but I saw that long hairs on filaments are due to wrong printing temps.

The MMU2S manual tells what is wrong and what is good but not the procedure to find the correct ending.

Help on this would much appreciated.

Posted : 02/10/2019 5:07 pm
Lichtjaeger
(@lichtjaeger)
Noble Member
RE: Filament calibration for having good ending and avoid MMUS2 got stuck

Stringing indicates that the temperature is to hight. But I wouldn't reduce the temperature to a level, where I lose layer adhesion.

In my opinion, you touched the correct settings. If you have a nice tip but that nasty little string I would higher the "Unloading speed at start" or even the "Unloading speed" itself, so that the string is ripped off before the tip reaches the gears.

Here some examples of my "Unloading speeds at start" as a reference:

PLA - 100mm/s

PETG - 120mm/s

PVA - 140mm/s

Posted : 02/10/2019 5:46 pm
David liked
michele.b3
(@michele-b3)
Eminent Member
Topic starter answered:
RE: Filament calibration for having good ending and avoid MMUS2 got stuck

Thanks for the ideas.

I am using PLA with 120mm/s and tmorrow I will implement your suggestion on PVA since there it is the filament I got most problems.

I am also developing 2 different PLA plus profiles since the temp depends on the producer of the filament so I got a higher temp (212-207°) and a lower temp (210-203°) since the one fits all rules does no longer work with MMU2S.

PVA is another issue since I want to use it for interface only but PrusaSlicer behaves a bit in a strange way putting a layer on the bed so that giving more problems on first layer printing.

What aboutn Number of cooling moves? Is it worth adding some? Is there any drawback with it?

Tx  

Posted : 02/10/2019 8:23 pm
Lichtjaeger
(@lichtjaeger)
Noble Member
RE: Filament calibration for having good ending and avoid MMUS2 got stuck
Posted by: @michele-b3

What aboutn Number of cooling moves? Is it worth adding some? Is there any drawback with it?

Tx  

Adding makes the tip thicker. Too less and the tip is stretched.

Posted : 02/10/2019 9:29 pm
huskyte
(@huskyte)
Trusted Member
RE: Filament calibration for having good ending and avoid MMUS2 got stuck

In my experience don't put too much effort into the tips. If you are printing PLA it is not the tips but heat creep by the extruder stepper that causes you the issues. Get an active or passive cooling solution for the extruder stepper and be done with it.  

Posted : 20/10/2019 9:18 am
michele.b3
(@michele-b3)
Eminent Member
Topic starter answered:
RE: Filament calibration for having good ending and avoid MMUS2 got stuck

Finally I have solved filament ending issues by:

- fine tuning the screws for the pressure on filament on both mmu2s and the extruder the more tight they are the more problems you will find in filament switching.

- nozzle temp if you face filament stringing during the switch try lower the temp for that filament. I saw that even 1 or 2 Celsius can make huge difference.

- take into account that prusa slicer has a bug with swicthing different filaments with different working temp since it unloads the filament with the next (and wrong ) temp. Waiting for prusa to fix please have a look to this https://forum.prusaprinters.org/forum/original-prusa-i3-mmu2s-mmu2-general-discussion-announcements-and-releases/mmu2-real-multi-material/#post-122360 to

get post processing script to be added to prusa slicer and work around the problem.

 

Posted : 20/10/2019 3:39 pm
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