First time with AA 0.25mm print core along with PVA

[frizatch 1]

First off, I've only been playing with my two Ulitmaker 3s for only a few weeks, so I'm new at this.  I appreciate any help for the naive!

 

I've successfully used a combination of AA 0.4 (PLA) and BB 0.4 (PVA) to produce some fairly detailed prints, but I'm trying to switch to an AA 0.25 for the PLA and my PVA extrusion is failing (the PLA is coming out fine).  Below is a picture of the PVA barely coming out in little disconnected spurts as it tries to put down a first layer outside of the black disc (yes, you can barely see it):

When printing with AA 0.4 PLA / BB 0.4 PVA, the test blob of PVA that comes out it substantial, but barely exists when I switch to the AA 0.25 for the other print core even though I can see the filament move some in the bowden tube (I don't think it's getting stuck in there).  I have let the Ultimaker Cura 3.3.1 use defaults for all the setting once I tell the interface what the material and print cores are... b/c honestly it's not obvious to me how to do otherwise.

 

Granted, I've struggled a bit with the PVA in the AA 0.4/BB 0.4 regime ... I have seen some infrequent carbonization and heard crackling, and the print often has floating blobs of PVA cruising around threatening nuisance.  I'm in Colorado, so it's fairly dry and my PVA is pretty dang new, but I have a call in to facilities to see what our ambient humidity is supposed to be in this building.  Largely, I'm wondering about the shifts the Cura software does to PVA delivery when the other print core becomes a AA 0.25.

 

Thanks in advance for hints/thoughts!

[frizatch 1]

To be clear:  I'm still using a BB 0.4mm for the PVA.

[gr5 2,000]

I've never tried pva when I used 0.25mm nozzle.  I'm wondering if there is a bug.  What did cura choose for the line width for the second core?  Ideally you want a line width around 0.2 to 0.25 for the .25mm core and a line width of 0.35 to 0.4mm for the BB 0.4mm core.

[kmanstudios 1,120]

Did you take the time to make sure it is not clogged? With PVA, that should be your go to option right off the bat. I just finished a print today that the PVA printed fine. In the time it took to take that off the plate and put on the new one and start the print, it clogged up but good. PVA is fickle stuff.

 

Do a series of hot and cold pulls to make sure. If that is not it, then I would look at what @gr5 posits.

[frizatch 1]

Update: it is possible it's a clogging issue.  I switched out printcore 1 back to an AA 0.4 and tried to do a print to see if the PVA in the BB 0.4 would just miraculously work... nope. I'll do some hot/cold pulls and try again with the AA 0.25.  Thanks!

[frizatch 1]

Yep, hot pulls / cold pull solved it.  Thanks for letting me know PVA is standardly a PITA!  So printing with PVA in BB 0.4 and PLA in AA 0.25 works... but my PVA still isn't pretty:

[kmanstudios 1,120]

If it pops and sizzles, it has moisture in the material. Does it pop and sizzle?

[frizatch 1]

Yep, it's a bit damp, for sure. I'm going to try the bake-out on a heated build plate (at 60) for a bit and figure out a method for our MakeLab to store PVA in smallish airtight containers with desiccant.

 

I'm happy to close this topic.. much of my PVA issues are covered elsewhere, I think ?

 

[kmanstudios 1,120]

Good luck and let us know how it goes.....just know that ou are on the right track...PVA is a pain....

[frizatch 1]

This is what came out of the print shown above... not too bad!  It's hard to see because it's a black print and the photo isn't great, but the figure has free-hanging tentacles for facial features.  Still has little traces of PVA after an overnight water bath, but the pick is useful for pulling some of them gently off.