PVA and Breakaway messy printing. Cooling issues?

[slg02 0]

Hi everyone! 

I already talked to support about this, sent them my BB print core for cleaning but while I wait, I'd like to get some opinions here.

My Ultimaker S5 wasn't doing well with PVA supports out of the box. Prints came off very messy, I have attempted to clean nozzle using cleaning filaments and PLA, but no luck, still lots of issues with printing.

 

This is what my regular PVA supports look like, PLA+PVA.

Cleaning didn't help much. I have a normal extrusion of cleaning filament when I do this. The only problem, probably, is cold pull - it's very hard do pull filament out and when it comes out, the end is still little soft (though I gave it enough time to cool down)

Anyway, sent my BB core back to manufacturer for cleaning, hopefully it helps but I have my doubts.

 

 

Swapped right core for AA core to try Breakaway PLA. Again, nozzle cleaned, did a small test print - all good.

First big print with it (1 day 8 hours) and I get this:

This is a 3rd party ABS with Breakaway PLA.

Same mess happens when I use Ultimakers Tough PLA with Breakaway, though in that case it's easier to clean.

 

 

Prime tower from same print:

 

Looked online for pictures of other peoples prints, supports look much cleaner than what I have even on best prints.

 

Can somebody give any hints to what might be wrong with my printer? Or maybe there's some settings in Cura i need to check?

 

To me it looks like the temperature might be too hot for these delicate support filaments and that's why we see all these strings and artifacts.

 

I also tried small test print with the same print core, loaded with CPE material (high temperature) - printed small hemisphere and it looked clean and consistent. So I assume problem is not with the core, but maybe something else?

 

Thanks,

[gr5 2,026]

That looks pretty typical.  I don't think anything is wrong with your BB core.  PVA does not stick to itself while still molten as well as PLA.  PLA comes out like a liquid rubber band while still hot.  PVA comes out like toothpaste, or cement, where it doesn't stick to itself and tiny chunks can fall.

 

You need to keep PVA super dry.  No one seems to get this.  You can't just put it in a bag with a little pack of dessicant.  You have to keep it at like 10% humidity.  Like a dessert.  If you leave it on the back of your printer for 4 days it is "ruined" and needs drying again.  I usually dry a spool of PVA on my heated bed with the temp set to 80C and with a towel over it overnight.  Don't go over 80C or all your PVA will melt.  But best to keep it dry with rechargable color changing dessicant.  Look that up on ebay.  You want boxes of dessicant the size of your fist.  Roughly. The dessicant needs to be recharged often.  That's why you need the color changing type to know how it's doing.

 

If it gets wet then it sticks to itself even worse.  If it gets VERY wet it makes sizzling noises while printing as you can hear the water boiling.  Those steam bubbles get into the PVA and cause problems.

[slg02 0]

hey, thanks for reply!

Yes that was probably what happened to my PVA as it absorbed some humidity while being stored. And yes, I heard quiet sizzling sounds when filament reached heated core. I'll try and dry out these PVA spools.

 

 

How exactly you dry your PVA spools, can you elaborate please? do I need to put something under spool for that, or direct contact with glass is okay?

 

Still I'm confused on why Breakaway PLA looks so messy, any ideas?

 

Edited June 4, 2019 by slg02

[johnse 31]

My breakaway also tends to have a lot of little curly pieces. I think what makes it a good breakaway is that it doesn’t bond well...but that means it also doesn’t build great structures. Sometimes the support overlaps the part and those strands get commingled into the part...

 

I’ve found that wider supports seem to work more cleanly, such as when supporting a wide shelf. Those tall, thin supports tend to break off partway through the print.

 

if you search cur settings for “expansion” you’ll find support horizontal expansion that defaults to 2mm. You might try increasing that and possibly increasing support infill percentage.

 

i had a small part with a short overhang I was printing in nylon. Cura didn’t put enough support there so I modeled a support block and did it as a 2-color print where the 2nd color was breakaway.

[geert_2 556]

For keeping filament dry, I use these bags with desiccant (left=package, right=actual bag), and keep all in a big sealed food box. The blue dot turns pink when moist. These bags can be dried in a microwave, or conventional oven at low temp. They can be found in car-accessory shops as they are used for drying car interiors. For reference: the ruler is in cm.

 

This is good to keep filament dry. But to actually dry already wet filament, it may not be enough: you may need elevated temperatures to first "shake the watermolecules loose" from the plastic, before this bag can absorb them.