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foehnsturm

Any experiences with dual extrusion and PVA?

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It looks like printing PVA is kind a nightmare. I managed to get good printbed adhesion and to print slow enough to get reliable results. Also I learned that fans are a no go.

But once PVA support starts on top of a PLA surface there's virtually no adhesion. Hey that's the main use case why I would consider using PVA ...

Any good advice?

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Hmmm... maybe the adhesion between PLA and PVA can be influenced with the thickness of the first PVA layer? Please don't ask me how to do e.g. a thin first PVA layer on top of PLA with the current software but it might be interesting to see if this is a way physically anyway.

Maybe rising the ambient temperature helps? Are you currently printing with an open printer at room temperature? What about a heated chamber for that purpose?

Just ideas...

Edited by Guest

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No real solution yet. So far:

Forget slicer created supports. Just make up a simple box shape and do a bolean subtract with the part. Use the remaining as support.

PVA doesn't stick to PLA. So, if you print PVA on top of a PLA surface make sure it isn't an island but instead connected to some PVA structure nearby. It will still curl up and need some millimeters height to recover.

I don't use stuff like priming towers. In this case there had to be to separate towers because of the poor adhesion I think.

Edited by Guest
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I have heard PVA doesn't wash off that easily as well. Have you experienced this?

I guess you wouldn't want PVA to melt into the PLA as it could dis-color it?? if this is the case then the adhesion between the two would be a difficult balance to allow it to stick but not melt into it.

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Probably the hardest thing I ever printed was a propeller.  This one came out very very nice!

PVA prints up to about 170C which is probably not hot enough to melt the PLA below it. Consider maybe covering the top and front of the machine such that the PLA is at it's glass temp? Not sure if that will help as then you need even more fan.

Maybe instead turn off the fan while printing PVA? And turn the fan back on when printing PLA?

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... and still collecting feature requests:

I had to set support / horizontal expansion quite high (3mm) otherwise support would sometimes start with super tiny blobs on a slanted surface (which don't stick at all). Obviously now all support structures are inflated but the intention is to modify only the tiny ones.

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