Printing problems with Filaflex Flex Shore A82 with MMU 2.0  

Re: Printing problems with Filaflex Flex Shore A82 with MMU 2.0

Hello Thomas,

Printing FLEX with MMU2 is currently not supported. I haven't tried it yet on my MMU2 but here is an idea how it might work:

1. Loading:
-> Slow with constant speed
-> Extruder gear need to drag at least at the same speed as the MMU2 gear is pushing. Better will be a slightly higher speed because it's a long part which can be dragged and it stress will be released as soon as MMU2 gears releases.
-> Slow and constant speed purge tower
2. Printing: Slow and constant speed printing
3. Ramming/Cooling:
-> This need to be rewritten. Current procedure will most likely chew up the filament. But it should be possible because my Ninjaflex tips in single print are looking fine.
4. Unloading: Should work without any issues.

Limitations:
-> It's hard to purge out PETG 255C filament with a FLEX 220C. One of the solution will be to load transition filament first (like PLA with 235C. Purge it and then load FLEX filament).

Anyway, I see it possible with the MMU2 hardware. Just the software (gcode) need to do the right thing.

Re: Printing problems with Filaflex Flex Shore A82 with MMU 2.0

it isn't the MMU2.0 by itself causing the problems.

the MK3 extruder itself can't handle soft TPU. this is one of the major problems of the MK3 design.

i run ninjaflex(shore 85a) and i run it on the MK2S as the MK3 cannot handle it.

part of the problem is the MK3 bondtech gears they chew up the filament way too much compared to the bearing idler design of the MK2 machine.

next prusa had to move the entrances for filament away from the bondtech gears setup to make clearance, this allows soft TPU to compress and "S" shape allowing it to jam the bondtech gears and then it forces itself out the sides rather then down into the extruder.
the gap used for the filament sensor also allows the soft TPU to jam and "S" shape again leading to failure.

a member about a year and half ago when the MK3 first came out and people started to realize prusa scammed us compared to the MK2s redesigned the R1 extruder for the MK3 so it could handle soft TPU however the fix didn't last there was overheating problems with the stepper motors and everything would melt after a few hours of TPU printing. prusa released the R2 extruder body and the TPU fix was redesigned for it but again it didn't last due to parts melting. there was a last fix where a lower guide was installed around the lower entrance to the extruder to try and give the TPU more support so it would not "S" bend and jam, but it really didn't work you got a few hours of printing then the entire system would melt and fail. When prusa released the R3 extruder body nobody ever ported the TPU fix into it and we all gave up. i only run TPU from my MK2S printers.

i was so discussed with my MK3 that i put it back in a box for 6 months until more bugs were worked out and i bought more MK2S machines. i've replaced everything printed on my MK3 at least 4 times now with revisions and fixes to try and fix what a mess it is compared to the older machines.

i was/am very vocal about what a mess the MK3 is. i consider it an experimental printer and do not use it for real work.

Re: Printing problems with Filaflex Flex Shore A82 with MMU 2.0

the MK3 extruder itself can't handle soft TPU. this is one of the major problems of the MK3 design.

Not true. I print Ninjaflex (85A) on my MK3 without any issues. Couple important things:
1. Release the pressure from the bondtech gears
2. Increase the nozzle temp if you encounter issues (235C is just perfect)
3. Print with constant speed 10-20mm/s (15-20 work best for me)
4. No retractions

Re: Printing problems with Filaflex Flex Shore A82 with MMU 2.0

the MK3 extruder itself can't handle soft TPU. this is one of the major problems of the MK3 design.

Not true. I print Ninjaflex (85A) on my MK3 without any issues. Couple important things:
1. Release the pressure from the bondtech gears
2. Increase the nozzle temp if you encounter issues (235C is just perfect)
3. Print with constant speed 10-20mm/s (15-20 work best for me)
4. No retractions

been there done that. i wrote one of those posts about settings. on a 40 hour TPU ninjaflex print your chance of failure is VERY high and you get to start over. with a MK2 100% reliability.

keep in mind i also converted my MK3 from the bondtech idler to a bearing idler like the MK2 design.

Re: Printing problems with Filaflex Flex Shore A82 with MMU 2.0

Been there done that. i wrote one of those posts about settings. on a 40 hour TPU ninjaflex print your chance of failure is VERY high and you get to start over. with a MK2 100% reliability.

keep in mind i also converted my MK3 from the bondtech idler to a bearing idler like the MK2 design.

I think everybody had issues with TPU on all machines at some point. I started with MK2. Then printed on MK3 and after upgrade MK2 -> MK2.5 had to learn how to do it on MK2.5.

Both of my machines are still stock and I'm printing with Ninjaflex TPU at 100% success rate on both machines.
The only hardware modification I had to do was on my MK2.5. During assemble I saw the extruder teflon tube is short. But it's beneficial for TPU if it's longer, almost touching the gears. So I made my own, slightly longer one.

Will say: For me it's working on stock MK3/MK2.5 hardware

Re: Printing problems with Filaflex Flex Shore A82 with MMU 2.0

I've successfully printed TPU and Ninjaflex on my MMU 2.0 but I've had to made a few modifications to make it reliable:

[*] https://www.thingiverse.com/thing:3233579 (PTFE pass-through connector back plate)
[*] https://www.thingiverse.com/thing:3337120 (Large bore selector--printed at .1mm layer height to make it extra smooth)

I've also swapped out the stock PTFE tubes with larger diameter ones (3mm ID/4mm OD) and created an entirely new universal spool holder that ensures there's always a constant gentle tension on the filament: https://www.thingiverse.com/thing:3406725

You should really try out my universal spool holder as it might solve your problems... You'll want to get yourself some skate bearings and 200mm M8 threaded rods along with some retractable ID badge holders and print the Retractable ID Badge Holder Clutch which acts as both a continuous slip clutch as well as an auto-rewind mechanism. It also has a bonus feature: When the extruder backs up the filament (for any reason--even simple retractions) it will gently pull back on the filament to ensure it doesn't spill out the side of the extruder (or the MMU 2.0).

Re: Printing problems with Filaflex Flex Shore A82 with MMU 2.0

I've successfully printed TPU and Ninjaflex on my MMU 2.0 but I've had to made a few modifications to make it reliable:

I've also swapped out the stock PTFE tubes with larger diameter ones (3mm ID/4mm OD)

Interesting ... usually ptfe tubes in higher quality closer to the actual filament diameter helps with flex. (E.g. Capricorn)

Re: Printing problems with Filaflex Flex Shore A82 with MMU 2.0

Interesting ... usually ptfe tubes in higher quality closer to the actual filament diameter helps with flex. (E.g. Capricorn)

That is most likely to be the PTFE tubes from the spools to the MMU2. Larger ID really helps with these for any filament.

Peter

RE: Printing problems with Filaflex Flex Shore A82 with MMU 2.0

Posted by: nikolai.r
Not true. I print Ninjaflex (85A) on my MK3 without any issues. Couple important things:
1. Release the pressure from the bondtech gears
2. Increase the nozzle temp if you encounter issues (235C is just perfect)
3. Print with constant speed 10-20mm/s (15-20 work best for me)
4. No retractions

I see this written a lot (release the pressure of the gear) but how can you tell if it is enough. Do you back of the idle screws while it is trying to load? Back it a lot and then tighten again?

This is something I would prefer not to experiment with as I don’t wish to have to de-clog  my hot end.

thanks