Printing with PVA Issues

[ytaseva 0]

Hello all,

This may be a question that has been answered before, but I was not able to find an exact answer to our issue.

We just got an Ultimaker 3Extended and are trying to print with PVA and white PLA, but are not able to print successfully with the PVA supports. The print always comes out with fly away print "hairs" and the PVA material interrupts the PLA print, ruining the finished product. Below are some example images.

We've tried reducing the PVA suggested temperature by 5 degrees to 220, and set the retraction distance to 6, but neither seems to help. Could this be an issue with the reel being exposed to humidity?

Any ideas or suggestions would be great, and thank you all for your help!

[gr5 2,167]

yes, pva is very hard to work with. I've had these same issues.

If the pva absorbs a lot of water you can hear it crackling/sizzling as it prints and boils the water. More likely the pva just isn't sticking well to itself or to some layer of pla. I'd like to see a photo of the pva nozzle when it's not printing - how much leaks out before it starts printing again? For me it's about 1/2mm.

One fix for this is a prime tower. You will still get these "holes" due to pva occasionally pooking a hole in your pla walls. But put the prime tower in the back center (not back corner where it defaults) because it is more likely to stick well near the leveling screw (back center) and so is less likely to fall over and make things even worse than without the tower.

Having said all that I'd like to see what your print looks like after you dissolve all that pva. I suspect you don't need any support for this print.

[ytaseva 0]

Thank you for the quick response!

I do hear a bit of crackling when it switches to the PVA nozzle (so maybe it has absorbed some moisture). It seems like the nozzle leeks about 1-2mm while it's not printing (image below).

We attempted the prime tower before, and it wasn't too much of a help (as it toppled over), but I'll try the different location. Attached are images of the model after the PVA dissolved. The geometry is pretty lean, but those interruptions of the PLA are pretty apparent. We had printed the model only with a PLA support, and that turned out much cleaner, but we are still trying to master working with PVA.

[gr5 2,167]

I guess I would indeed use pva for that. Does your pva really hang over air like in the second photo at the top of this topic (left side of part)? If so then that's a problem right there. Play with support settings - maybe increase horizontal expansion for support or decrease distance between support and part. And try the prime tower in the back center. If the tower is falling over you should concentrate on that issue. Mostly move the rear screw half turn CCW to really squish that first layer of the tower into the glass. Bottom layer squish is critical to getting parts to stick to the bed.

[tomnagel 126]

Have you tried printing with Cura 2.4 or 2.5, with all settings at default?

The default printing profiles are pretty good, and should give hard-to-beat results with most models. Try to stay away from custom mode before you have had good results with recommended mode.

[randyinla 14]

I've only had my U3e 4 days and have only printed one thing that needed PVA support. Since the PVA is intruding into your PLA area, could it be your X/Y calibration needs to be tweaked? Granted, it doesn't look like a uniform intrusion, just partial here and there.

[Joade 0]

Hi, Same issue when printing with PVA :

Machine : ultimaker 3+ , AA-PLA BB-PVA.

Description of the problem : after a printcore swap, the BB printcore continues to extrude slowly some PVA for some (long) time, while already printing with the AA core. this leads to bits of PVA all over the place, sometimes inside the PLA (leading to holes in PLA after dissolving PVA)

I've tried to play a wide range of temperature for the PVA : no luck.

I've tried to play on the retraction : maybe a small enhancement, but not a great success.

I've tried to bake the PVA: no improvement. (i don't think it's a moisture issue. When the PVA is baked, the bubbles and the yellowish color due to the water have vanished... this slow leaky extrusion continues.).

Some intersting hints :

The PVA support I made using an other slicer than Cura (It's a commercial software... May I name it here ?) are perfectly clean ! No slow leaky extrusion at all !... unfortunately, for many reasons, i like cura better... and i would like to be able to use cura for dual extrusion with PVA too.

So i think the default PVA settings of cura are not that good... Maybe someone could inspect some G-code i made with this other slicer, and understand the difference with the default cura settings for PVA ?

Best regards

Joade !

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