Extend or move PTFE tube to help printing flexible material on MK3S+?
 
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Extend or move PTFE tube to help printing flexible material on MK3S+?  

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jfedullo
(@jfedullo)
Active Member
Extend or move PTFE tube to help printing flexible material on MK3S+?

Hello,

     I am relatively new to 3D printing.  I have a MK3S+ and have been printing flexible materials with mixed success.  The parts are door bumpers for an antique car.  (Stanley SteamCar)

     I have been able to print it in Fillamentum Flexfill 98A without any issues using the standard settings within the Prusa Slicer.  Unfortunately, it is too stiff for the application.  I went to Fillamentum Flexfill 92A and I have about a 75% success rate, but the parts are still too stiff.  I have modified the part geometry, and reduced infill to 14% concentric to geometrically soften the part, but I would like it to be more flexible still.

 

     I ordered Filatech FilaFlex 30 and 40 and have had zero luck getting either to print with the standard settings in Prusa Slicer.  The FilaFlex 40 sorta prints for a little while but always ends up under extruding or clogging before the part finishes.  The FilaFlex 30 will not print at all.  I can't even get it to "Auto Load" the filament.  I have to load it manually by slowly manually jogging the extruder axis.  Once loaded, it will not print at all -  it just wraps around the extruder wheels.  It feels about the right stiffness and I would really like to print with it.

 

     I have varied the drive wheel tension screw from 1/4 turn to 1 turn in 1/4 turn increments without success.  I have tried upping the hot end temp 5C, then 10C without success.  I have tried reducing the print speed to 15. 

 

     Some internet searching advised extending or adjusting the PTFE tube in the hot end such that it just barely clears the drive wheels.    There is plenty of gap between my PTFE tube and the drive wheels and I think the soft flex material just squirts out.   Can I install a MKS3 PTFE tube (2mm longer) or just slide the original PTFE tube up closer to the wheel?

https://forum.prusa3d.com/forum/original-prusa-i3-mk3s-mk3-how-do-i-print-this-printing-help/extruder-mods-that-help-flex-filament-printing/

https://help.prusa3d.com/guide/how-to-trim-ptfe-tube-original-prusa-printers_22424

 

Thanks!

-Joe

Posted : 24/05/2022 9:09 pm
Diem
 Diem
(@diem)
Famed Member

infill to 14% concentric to geometrically soften the part, but I would like it to be more flexible still.

Concentric fill is still compartmented and internal air pressure contributes to stiffness.

Try using one of the uncompartmented fills, eg. gyroid, and then use a modifier to connect the interior and exterior - much softer.

Cheerio,

Posted : 25/05/2022 12:52 am
jfedullo
(@jfedullo)
Active Member
Topic starter answered:
RE: Extend or move PTFE tube to help printing flexible material on MK3S+?

Thanks for the tip on infill.  I have used gyroid and for this part that made it stiffer.  I have about 25 prints of the part I used to tweak the geometry to soften it via design.

I would really like to be able to  use the softer filament I have purchased.  Any tips on how to get it to feed?

Thanks!

Joe

Posted : 25/05/2022 6:36 am
Neophyl
(@neophyl)
Famed Member
RE: Extend or move PTFE tube to help printing flexible material on MK3S+?

You don't want to move the ptfe tube up.  For a start that will leave a gap at the bottom and secondly it will gradually just move down again due to friction.

You could fit a replacement ptfe tube that is longer and sculpted for the gears.  For example the Bunny & Bear extruder uses such a ptfe tube, see https://bunnyscience.dozuki.com/Guide/Bunny+and+Bear+(BNBSX)+MKS3+Geared+Extruder+Assembly/2#s97

Now I am not saying to use that one as the length probably wont match as that is a complete custom extruder rebuild, I only use it as an example of what you would need to do, just customise the total length to fit your setup.  You could probably use their jig for the curved top that fits near the gears though.

A quick google found this https://3dmixers.com/m/91122-ptfe-sculpting-guides-for-tight-filament-constraint   

Posted : 25/05/2022 7:20 am
Same Old Shane
(@same-old-shane)
Admin
RE: Extend or move PTFE tube to help printing flexible material on MK3S+?

I am not familiar with the particular version of flexible filament you are working with, but I wonder if it is similar to ninjaflex which is much softer/flexible than the filamentum brand. You could try and modify one of the existing flexible filament profiles. 

To load it what you could do is turn off autoload, then trigger the printer to load filament, the gears will start to turn fast, when they slow down, THEN insert the filament and provide a little resistance on the filament being loaded, the printer will ask if the filament is clear, select no for it to continue to load slowly. You could also try and adjust the print speed to print slower and depending on the softness of the filament, maybe turn off retraction as well. 

There are a few older guides for printing flexible filament, I found that Maker Muse has a good video to use as a guide when trying to get different flex filament to work right.

Hope these help .

Shane (AKA FromPrusa)

Posted : 25/05/2022 8:24 am
jfedullo
(@jfedullo)
Active Member
Topic starter answered:
RE: Extend or move PTFE tube to help printing flexible material on MK3S+?

Shane,

     Thanks for the tips.  The FilaTech FilaFlex30 is very soft.  I don't have any Ninjaflex, but they may be similar.  It is WAY softer than the Filamentum FlexFill 98.  I ordered it in part because there were settings for it built into the Prusa Slicer.  I started from the Prusa settings for the actual filament I was using, but they do not come close to working on my machine.

     With the FilaFlex30 (Softest stuff I have seen ) I can only get it to load manually.  Essentially I turn auto load off, heat the nozzle, then manually advance the Extruder axis very slowly.  That gets it in the machine, but it doesn't print at all.  Even if I contimue to slowly advance the extruder axis, the FilaFlex30 just buckles and wraps around the drive wheels.

 

Thanks,

-Joe

 

 

Posted : 25/05/2022 11:26 am
jfedullo
(@jfedullo)
Active Member
Topic starter answered:
RE: Extend or move PTFE tube to help printing flexible material on MK3S+?

I dug into things yesterday and It doesn't look like the PTFE tube can be extended on the MK3S+.  

I had read of people doing it succesfully online, but that was on earlier printers.  On the MK3S+, the teflon tube does not stick up to the drive wheels because there is a 3D printed part that is on top of the PTFE tube.  The 3D printed part fits tightly to the drive wheels when the door is closed. 

I played with settings more for a while yesterday and am still basically in the same place.  The softest filament (FilaTech FilaFlex30) doesn't print at all.  I can get a few drops out of the extruder sometimes, but nothing close to printing.  I can get the mid filament ( FilaTech FilaFlex40) to print, but it way under extrudes.

I tried a softer spring on the extruder wheels, but it didn't seem to help.  I am going to get a longer screw for that door and see if that helps me.

Kinda frustrated - I bought these filaments because they were in the slicer database and thought I would have a little more luck than this.  If the longer door tension screw doesn't help, any other ideas?  Should I get a different extruder?

 

.  It looks like the MK3S+

Posted : 26/05/2022 12:11 pm
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