Extruder mods that help flex filament printing
I commented elsewhere about a Thingiverse.com "Thing" that I designed to help prevent flexible filaments from "bulging out"of the extruder. I thought it deserved wider exposure, and so decided to post this dedicated topic. I found that most flex failures resulted in the filament bulging out on the left-hand side, so I designed an insert for the extruder that provided a "blade" or "shelf" that constrains the filament in that area. It is posted on Thingiverse.com as https://www.thingiverse.com/thing:3361565 . After using it for a while, I begin to have bulging failures on the right-hand side as well, so I redesigned the pressure door with a similar constraint. That mod has now been added to the "thing" and I encourage folks having a look at it if they are having problems printing flex. I also encourage Prusa to incorporate these mods into current and subsequent production. They help printing flex and don't interfere with other filaments as far as I can tell.
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Re: Extruder mods that help flex filament printing
Hello John,
Thanks for sharing. Based on my experience it doesn't make big difference if you try to limit the space around the gears.
In the picture I can see you've already increased the length of the PTFE tube, so it's almost flush with the gears. This is the best situation you will get. From there it's just about the flex grade and the back pressure (temp+speed). If the back pressure is too high, the filament will be pushed out hard way from all the sides or winding up on the gears. You might get bigger troubles if you close everything.
So far the solution for all flex grades on MK3 was for me:
-> constant speed ~20mm/s
-> high temp ~230C
-> no retractions (based on the model it sometimes work with retraction)
-> enough space for the first layer
100% success rate with Ninjaflex (85A) so far and my PTFE tube is not even so high placed like yours.
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Re: Extruder mods that help flex filament printing
Actually, I didn't make any changes in the positioning of the PTFE tube. I think the lighting in the photo makes it look like it is higher but it is no different than before the mods.
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Re: Extruder mods that help flex filament printing
Actually, I didn't make any changes in the positioning of the PTFE tube. I think the lighting in the photo makes it look like it is higher but it is no different than before the mods.
Then you assembled it slightly different then me. Mine sits almost flush with the lower ring of the plastic.
Often linked posts:
Going small with MMU2
Real Multi Material
My prints on Instagram
Re: Extruder mods that help flex filament printing
I'm having trouble visualizing what you mean by the positioning of the PTFE tube. Can you post a picture? Also, where is the option to select "no retractions"?
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