Am I wasting time trying to get MK2 MMU to work with Nijaflex?
I'm a newbie, but follow instructions really well. I've gotten the Mk2 MMU at a local maker space using PLA to print some high quality parts. I need a few parts to print with flexible filament but the Nijaflex I've tried won't extrude after loading so I haven't been able to try printing yet.
After several days of researching and experimenting it looks like the problem is an under constrained extruder. Basically, the 85A filament finds a sneak path out near the Extruder idler. Temperature is preheated to 230.
I'm wondering if the MMU requires more force from the extruder. Does anyone know if this could be an MMU specific problem?
I was looking at the Extruder idler MM part and thought maybe I could modify it slightly for a better constrained path. Does that even make sense? I found STL parts for the MMU but I don't see the exact one I have for some reason. Does anyone know where I can find a model of this part?
Thanks in advance for any help or advice.
Re: Am I wasting time trying to get MK2 MMU to work with Nijaflex?
look at https://shop.prusa3d.com/forum/original-prusa-i3-mk2-multi-material-f26/ninjaflex-and-the-extruders-t5655.html
his extruder can be downloaded and printed.
Re: Am I wasting time trying to get MK2 MMU to work with Nijaflex?
Flex is problematic at best with Bowdens. I had some success at very slow speeds with an UM2+, but that is on 3mm filament.
Basically you need a short distance between extruder and nozzle, because the filament can laterally compress. It is worse for 1.75 mm, which also has more diameter tolerance issues. Also you need a very constrained filament path with a constant diameter throughout. In the MMU system the internal diameters change several times (even in the heatbreak), and the sides of the extruder are open.
If you need Ninjaflex, a massive redesign is needed. I think a hybrid head with 1 direct drive for Flex and 3 Bowden for other filament is the way to go. Obviously no easy task. I'm sure it can be done but you also must consider the effort for tweaking the gcode (and maybe firmware).
I had some success with Flexfill 98A, but then had to change to Seths all-plastic multiplexer. Since then the filament blocks up by compression above the nozzle. I've given up and plan to build a cheap-ass direct drive printer specifically for Flex.
Re: Am I wasting time trying to get MK2 MMU to work with Nijaflex?
No you are not wasting your time trying to print ninjaflex on you MMU. I have the MMU and i have successfully printed with ninjaflex.
I found that the best thing to do is to remove the multi material adapter from the top of the hot end and place one of the PTFE tubes directly into the hotend.
You need to loosen the tension screws on the extruder so that they are fairly loose and you also need to slow the print speed down to 20mm/s.
when the print starts i usually keep some tension on the filament so that it cannot come out the side of the extruder, and if it does come out then pull it out until the blockage is clear.
Finally i turn the temperature up to 240 and the flow rate to 110 on the printer.
Once you get the first layers down the rest should flow nicely and you should get a nice print.
Oh and one more thing, make sure that you turn of any sort of retraction as this will cause jams.
Good luck and happy printing 🙂
Re: Am I wasting time trying to get MK2 MMU to work with Nijaflex?
I have yet to try Ninjaflex with my MK2S MMU. I have been having decent luck with the Sainsmart TPU, but it's a bit stiffer. I was getting a lot of filament escapes from the extruder until I slowed the print way down (15 mm/s) and set the retraction speed quite low (50 mm/s). Once I did those two things, everything worked just fine.
Running a tube all the way down into the hotend is a clever idea. I'll keep that in mind for the future.