with MMU2 last millimeters of an extrusion are always missing
 

with MMU2 last millimeters of an extrusion are always missing  

  RSS
thomas.s13
(@thomas-s13)
Active Member

Hello,

I am  also missing the last 1 to 4mm of the last extrusion parts on a print, which can be very visible with the MMU2 on a MK2s.

where the last retraction takes place the printer skips the last necessary part of the filament.

In the photo u can see the missing red on top.

How can i prevent this?

I did the procedure to adjust the steps from the mmu2 to the extruder gears, but this had no influence on this? Seems the printer stops to extrude too early. 

This topic was modified 7 months ago by thomas.s13
...
Posted : 21/02/2020 5:21 pm
vintagepc
(@vintagepc)
Noble Member

Have you calibrated or altered the linear advance (K) value for your filament?

Posted : 21/02/2020 5:47 pm
thomas.s13
(@thomas-s13)
Active Member

no i have not, would that be a possible solution? I didn´t print with linear advance by now

...
Posted : 23/02/2020 2:36 pm
vintagepc
(@vintagepc)
Noble Member

Yes, it should help. bad linear advance values show up as over or underextrusion at the start and end of extrusions because the printer isn't compensating for the behaviour of the molten filament correctly when it is under pressure.

Are you sure that's the end of the extrusion line and not the start? If it's the start, you can (after calibrating linear advance) play with the 'extra length on restart' filament property for filaments with this issue.

If it's truly the end of the extrusion.. .turn off 'wipe while retracting'. That should not be necessary with a good  K value. 

 

 

Posted : 23/02/2020 2:59 pm
thomas.s13
(@thomas-s13)
Active Member

Vinagepc, you were right, it is the beginning not the end of the last layer where the filament was missing. I could just figure it out with a g-code analyzer, because the printhead of the prusa is so large. I am starting with the measures you proposed.

...
Posted : 24/02/2020 6:56 pm
vintagepc liked
vintagepc
(@vintagepc)
Noble Member

Best of luck, you might also try dropping the filament temperature a bit if you can. Some are extra oozy and leak out during travel moves, leaving a void where there is normally filament.

Posted : 24/02/2020 7:15 pm
thomas.s13
(@thomas-s13)
Active Member

The setting  'extra length on restart'  really solved the problem, Thank you!

...
Posted : 13/03/2020 6:24 pm
Share:

Please Login or Register