Flexible filaments and MMU2S  

Re: Flexible filaments and MMU2S

No one?

Re: Flexible filaments and MMU2S

i dont have my MMU until next month but i would assume printing flexible filaments should be no problem as its still a direct drive extruder.

You should probably change some settings to have the filament fed into the extruder slower than for PLA but it should work.

Re: Flexible filaments and MMU2S

if it's a single material print, you could 'load to nozzle'.

then use the mk3 non mmu profile to do the print

regards Joan

Re: Flexible filaments and MMU2S

Thank you Joan, I’ll give that a try.

Re: Flexible filaments and MMU2S

I have yet to try flexible filament now that I've upgraded the extruder, but plan to this weekend. If you find that the filament binds in the tube during the push move from the MMU, before the bondtech gears grab it at the extruder, you can also decrease the load speed for flexible by going to Filament Settings > Advanced. Make sure you have the correct filament type selected in the pulldown menu (or create one if it doesn't already exist) and then lower the Filament Load Time. It seems that every one of the default filaments loads at 15mm/s which may be too fast, especially for a super low Shore hardness filament like X60.

RE: Flexible filaments and MMU2S

Posted by: Peel

 It seems that every one of the default filaments loads at 15mm/s which may be too fast, especially for a super low Shore hardness filament like X60.

I tried to print with Ninjaflex and X60 with the MMU2. I couldn't load the materials to the nozzle reliable but I didn't try to decrease the loading speed ... also the extra loading distance helped a little ...

I have the S update but haven't installed it yet. Maybe the new sensor helps with a more reliable loading?

RE: Flexible filaments and MMU2S

Yeah so that's what brings me here today.   I have MK3S and MMU2S, tried printing with TPU flex and the filament got wrapped around the bondtech gears and started coming out the side.

To clean up I have to remove the door, some screws, cut the filament and remove in pieces.

I am afraid to load it again.   However, load to nozzle might be worth a shot.

RE: Flexible filaments and MMU2S

However, load to nozzle might be worth a shot.

Its worth a shot, but it didn't work for me. I have been pulling my hair out all night trying to get flexible filament to work. The issue isn't with the MMU itself for me, but the extruder sensor. The squishines of the filament makes it so it doesn't push the lever enough to trigger the IR sensor. I had to adjust the sensor stack as far right as it will go, and loosen the tensioning screw until it is flush with the nut on the right. Now it at least it is sensing the filament, but for some reason after what would have been a successful load (I think it would have been successful?) it just backs it all the way back up the the MMU, and then tries again, and then sends it back up the the MMU again, and then asks if it is extruding with the correct color. no idea where to go from here. 

RE: Flexible filaments and MMU2S

@dane-r2 : Same issue here, see picture in my other post. I tried both direct and MMU2S feeding, problem is the auto-unloading after the loading of the material, I don´t even know why the printer is doing this.

RE: Flexible filaments and MMU2S

I think there are two problems:

1) soft flex: like said by @travis-o : thight bondgears will squish the filament and there is no detection that filament is between the gears. Possible fix: make the sensor more sentive according to @travis-o suggestion above

2) all flex: with the MMU2 there is a replacement PTFE tube for the extruder. This one is a bit shorter. Therefor there is a bigger gap between the gears and the tube. Instead of going straight down in the tube, like regular filament, flex filament bends slightly and escapes through the small gap and winds itself around the gears.

fix: ??  (The older longer tube does not work that well in making nice points to the filament upon unloading.)

RE: Flexible filaments and MMU2S

i found an issue that explains a lot: missalignment in the filament path

https://forum.prusa3d.com/forum/original-prusa-i3-mk3s-mk3-user-mods-octoprint-enclosures-nozzles-.../modified-c1-r4-mk3s-parts-better-filament-path-and-a-version-for-mk3-sensor/

RE: Flexible filaments and MMU2S

I gave up trying to shove a rubber string down all that tubing.  My solution....unscrew the mmu2s circuit board holder and disconnect the mmu2s data cable.  Put the board back on so it doesn't flop around.  Disconnect the UPPER ptfe screw connector form the mm2s, snap on the old mk3 spool holder to the frame next to the mmu2s and put the tpe spool on there (under roll feed).  Tape the tubing in place to the top of the frame, facing the spool and feed the tpe directly down that short tube to the extruder as if it was the old mk3/s.  Turn on the printer, and voila it thinks it's the old mk3.  Load filament as on the mk3.  Keep the tension on the idler low.  First try - perfect print.  And this was my very first load of TPE.  Works great.  Not pretty....I'll design and print a holder for the tubing into the extruder soon for my tpe printing.  I'd use it - it keeps the kinks out and keeps a smooth path.  TPE feeds /prints at a slow rate so the spool fed the extruder with no problems.

Ideally I'd like to try the tpe in mmu2s but I have a sneaky suspicion that it won't be worth the time and effort.

RE: Flexible filaments and MMU2S

Hi

Today I've tried flexible filament for the first time with the MMU2S, because I want to print something in-between parts. So I’m not interested in single material prints.

I know my filament is probably a bit too flexible with Shore 30D (Fiberlogy FiberFlex 30D).

I had 3 fails until I got it working:

• The filament reached the extruder gears but didn’t make it into the heater, since the gears didn’t catch it. I fixed that with loosening the idler door screw.
• I got the print starting, but everything was too fast, so the filament tangled around the extruder gears.
• I switched the max. print speed to very slow (20mm/s) and the cleaning line looked ok in the beginning but is was still way to fast. Again the filament tangled around the extruder gears. 😐 

I then manually changed the g-code, to lower the first line speed and this is the result 😎 :

RE: Flexible filaments and MMU2S

And here comes the disappointment. I probably won't be able to print both materials with MMU unattended just because the tension of the idler door is totally different for the materials. For PLA and others, I need a lot of tension and for the Flex it should be very low.

I just changed it during the print and helped a bit, so I got this multi-material part. Pretty cool and I wish I could print like this all the time.

I will do some investigations on the extruder gear speed when loading the material. It might be way too high so the teeth can't grab it. If I adapt this maybe the tension can stay during the print. I will let you know...

RE: Flexible filaments and MMU2S

Well, marvin-b managed to use ABS, PETG, PLA, PMMA and Flex in a single print. See his post on the forum:

https://forum.prusa3d.com/forum/english-forum-awesome-prints-hall-of-fame/i-finally-did-it-successful-mmu2s-print-with-abs-petg-pla-pmma-and-flex/

Sonds like it wasn't all that straightforward, though.

RE: Flexible filaments and MMU2S

Cool. Thanks! I'll have a look into that!

I wish I could do it with simpler actions, but the MMU doesn't seem ready for that yet.

RE: Flexible filaments and MMU2S

Unfortunately he hasn't provided any details what he has done.

RE: Flexible filaments and MMU2S

Posted by: geki

And here comes the disappointment. I probably won't be able to print both materials with MMU unattended just because the tension of the idler door is totally different for the materials. For PLA and others, I need a lot of tension and for the Flex it should be very low.

Don't give up fast. The idler tension is not critical and can be compensated by reducing the pressure required to push it. (like going slower, let filament more space, time, higher temp to flow with less resistance).

You could also consider using softer PLA filament like Polyalchemy.

RE: Flexible filaments and MMU2S

@nikolai-r

I already continued getting it run. The tension is indeed not as important as I thought. If the extruder gears are slow enough, the tension can be high or better said, stay the same for all filaments.

As I mentioned in another post, the only reason I can't print flex filament is the speed of the extruder gears while loading, which I can't adjust. Besides that my prints come out beautifully. The rest are filament dependent adjustments and has nothing to do with the MMU.