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Trouble with a specific texture  

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Dave G
(@dave-g)
Eminent Member
Trouble with a specific texture

I am having the strangest problem. Printing the floor tiles from the Dragonlock set here:  https://www.fatdragongames.com/fdgfiles/?page_id=2658

Printing on my Prusa MK3S with EcoTough PLA from Filaments.ca and while everything prints fine for the first while, as soon as I hit the 'rocky' tops of the tile, the printer jams 60% of the time or so. Basically, it stops feeding, although I can clear the jam just by ejecting the filament, trimming it, and reloading it. The filament always has a section where you can see that the bondtech gears have gouged out an area so that explains why it can't feed, but *WHY* is it doing this repeatedly at the same spot on these tiles. Even when I do get a completed print the tile tops aren't smooth and stone-like, they are pointy and rough.

Settings are using the .2mm Quality presets in Slic3r with the only change being that I add a brim and set it to 5 layers for top and bottom since the designer suggests that. My only thought is that since the texture is so uneven that the repeated action of extrude/retract/z-hop/extrude for small sections is grinding the filament.

What should I try to resolve this?

Posted : 14/05/2019 4:17 pm
JoanTabb
(@joantabb)
Moderator
RE: Trouble with a specific texture

try reducing retraction length. 

Default is 0.8mm

try 0.4mm

 

Joan

 

I try to make safe suggestions,You should understand the context and ensure you are happy that they are safe before attempting to apply my suggestions, what you do, is YOUR responsibility. Location Halifax UK...
Posted : 14/05/2019 8:14 pm
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(@)
Illustrious Member
RE: Trouble with a specific texture

As Joan suggested ... 

There is a mechanism that combined with a Prusa specific modification in the V6 heat break and large numbers of retractions the filament melt is pushed up into a wide region of the heat break, where it cools and jams.  Unloading the filament after a jam of this type reveals a 2.2 mm stub as shown here:

Posted : 14/05/2019 9:42 pm
Dave G
(@dave-g)
Eminent Member
Topic starter answered:
RE: Trouble with a specific texture
Posted by: Tim

As Joan suggested ... 

There is a mechanism that combined with a Prusa specific modification in the V6 heat break and large numbers of retractions the filament melt is pushed up into a wide region of the heat break, where it cools and jams.  Unloading the filament after a jam of this type reveals a 2.2 mm stub as shown here:

Bingo that's exactly what I was getting, followed up by the Bondtech gears chewing the filament.

So the solution is reducing the retraction?

Posted : 14/05/2019 9:48 pm
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(@)
Illustrious Member
RE: Trouble with a specific texture

I replaced my heat break ... lol.  But try Joan's approach first.  It can help 'prove' the theory.  You can also increase nozzle temp by 20c and sometimes that gets the transition zone that last mm up the heat break to where the issue goes away. 

Here's an image of the special heat break: check where it changes from 2.0 mm to 2.2 mm ... if that step is at the plastic melt point there isn't a problem. If it is cool and the plastic solidifies, you get a jam.

Posted : 15/05/2019 3:13 am
Dave G
(@dave-g)
Eminent Member
Topic starter answered:
RE: Trouble with a specific texture

Running a batch off now, so I guess I'll know in the morning.

Posted : 15/05/2019 3:15 am
Dave G
(@dave-g)
Eminent Member
Topic starter answered:
RE: Trouble with a specific texture

So far so good.  Still printing when I left for work so I didn't check the texture but it didn't jam so that's a start.

Posted : 15/05/2019 11:46 am
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