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[Solved] MMU2S PETG + PVA Does not work!!  

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jake.m3
(@jake-m3)
Eminent Member
MMU2S PETG + PVA Does not work!!

So i got the MMU2S today, tried some PETG + PVA and am sad too see that this is not possible.

When switching to a different filament, the guy who coded the mmu2 thought when purging, it's a good idea to go from 10-100mm/s in the span of 2 secconds. And that results in this fine mess:

So i have wasted 300 Euros + a day for a feature that does not work as advertised.

And yes i have tested PVA + PETG temps from 190c - 260c with no difference.

The purging logic as it is now is like starting the first layer of a print on an oily surface at 100mm/s, i can't see how the guy that coded this thought it was a good idea.

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Posted : 20/08/2019 10:31 pm
muddymaker
(@muddymaker)
Trusted Member
RE: MMU2S PETG + PVA Does not work!!

Hi Jake-m3,

I too am unsuccessful in printing with PVA supports either with PETG or PLA.

The main reason I bought the MMU2S was so I could utilise water soluble supports in my prints. I don't care too much for multi coloured prints.

What's amusing to me is that I tried printing the Hilbert cube you have posted and had the exact same problems haha.

I used esun's natural PVA which has a print temp range of between 180-210 degrees celsius and it doesn't cost an arm and a leg to buy here in Australia. Perhaps I need to try Primaselect or Verbatim PVA soluble support as they seem to be the only ones that Prusa have tested and approved for the MK3S-MMU2S , unfortunately these aforementioned brands of PVA materials from Prusa are exorbitantly priced.

Maybe someone out there has mastered the art of using soluble supports with the MK3S MMU2S and would like to demystify the process for us new users, please chime in now, thanks in advance, Tony.

*holding my breath* 

My post is to merely commiserate with you as I have nothing helpful to add.

Posted : 21/08/2019 10:45 pm
Paul Mullen
(@paul-mullen)
Active Member
RE: MMU2S PETG + PVA Does not work!!

I have a roll of the Primaselect that I have not been able to use in the MMU.  My hypothesis is that the surface of the filament is rough (at least compared with PLA, ABS, and PET-G), and this is causing friction problems that make everything else not quite right.

Anyone have experience with the Verbatim or other soluble materials?

Posted : 22/08/2019 4:28 am
Kamil
(@kamil-3)
Eminent Member
RE: MMU2S PETG + PVA Does not work!!

It might work to split the wipe towers into 2 towers. One for PVA and second for the rest etc. PET. It might solve the problem. Try to increase the purge volume?

Posted : 22/08/2019 9:35 am
jake.m3
(@jake-m3)
Eminent Member
Topic starter answered:
RE: MMU2S PETG + PVA Does not work!!

Good news everyone, the reson for the filament curling up is because some genius set the "Extra loading distance" in printer settings to -25, the correct value should be -15.

Temps: PETG 245C & PVA 225C

The reason for the curling is the filament not being in the correct location before the nozzle starts wiping.

Before: Slow wipe ------- filament exits nozzle -- fast wipe

Now: Filament exits nozzle -- slow wipe ----- fast wipe

Note this fixes the wipe tower not the failed loading.

This post was modified 2 years ago by jake.m3
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Posted : 22/08/2019 10:01 am
Kamil
(@kamil-3)
Eminent Member
RE: MMU2S PETG + PVA Does not work!!

I would not recommended to go with so high temperature with PVA. It is recommended not to pass 200C

'The brand of filament you’re using affects the printing temperature for PVA. For MatterHackers PVA filament, print at 185±15°C, or if you’re using Ultimaker PVA, print it at 215±5°C. Don’t push it much higher than these temperatures, because PVA is very prone to cooking and carbonizing in the nozzle. In other words, it clogs easily, so make sure you keep your printing temperatures low and retract the filament from the nozzle when not in use. '

https://www.matterhackers.com/news/how-to-succeed-when-3d-printing-with-pva-support-material

Regarding load filament, check an idler if it is not broken or/and screws are not lose. I had the same problem and I needed to replace it.

Good luck.

 

 

 

Posted : 22/08/2019 11:42 am
Bart Lee
(@bart-lee)
Active Member
RE: MMU2S PETG + PVA Does not work!!

I am not sure how the "Extra loading distance" works but today I found that by making sure there are no colour changes in the first 3 print layers, the wipe tower copes ok with the really fast nozzle movement after that without tearing it up and having curled up plastic sticking to the outside of the nozzle.

I installed Prusa Slicer 2.1.0 yesterday and flashed my mk3s and mmu2s with latest firmware  as well and still have another problem which is under extrusion immediately after the nozzle exits the wipe tower. But I have solved this by printing a skirt 2 perimeters wide for the same height as the print. It wastes plastic, but it works.

Posted : 20/11/2019 10:22 am
Alexey S.
(@alexey-s-2)
New Member
RE: MMU2S PETG + PVA Does not work!!

Is PrimaSelect PVA+ compatible with Prusament PETG?

I see on PVA page ( https://shop.prusa3d.com/en/special/169-primaselect-pva-soluble-support-500g.html ):

Nozzle temperature: 205-210 °C
Bed temperature: 50-60 °C (Bigger object bigger temp.)

And on PETG page ( https://shop.prusa3d.com/en/prusament/802-prusament-petg-jet-black-1kg.html ):

Nozzle: 250 °C
Heatbed: 80-100 °C

Is going to work? Which temperature should I set?

On PVA page it says:

  • 3D Prima's new formula for PrimaSELECT PVA+ is more stable to print with than regular PVA. This also means that it bonds much better than regular PVA to PLA, ABS and PETG.
  • Tested and recommended as soluble supports for our Multi Material upgrade.

Did anyone try?

Posted : 29/11/2019 3:37 pm
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