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Marvinester

Help! PVA keeps on failing

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This past week, every print with PVA has failed on my Ultimaker 3. 

Here is what I have done so far. 

1. For example, during print#1 shown below, it stopped extruding PVA (printcore was just going around without PVA extruded). 

2. I baked PVA on Ultimaker build plate at 50 degreeC for 2 hours.

3. Hot-pulled the hotend until clean. 

4. At the start of print#2, PVA was extruded clean. 

5. During print#2, PVA extruded better with no missing gaps, but stopped extruding at nearly the same level as print#1.

6. Feeder's moving back and forth ok. (however PVA at the feeder's been grinding to a varying degree to the point where for a large print it snapped)

7. I've always kept the filaments in a sealed bag with desiccant.

8. I'm using UM filaments.

 

I'm really hoping that someone can help me out here!

Thanks.

Picture2.png

Edited by Marvinester

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I understand you have kept your filaments in bags with dessicants.  That might not be enough.  How long ago was the PVA first used? 

 

To my eye, it does have the look of humidity.  I use a filament dryer, dried my PVA completely two weeks ago and sealed it with fresh dessicant.  I could hear it popping as it printed today. One area of a support failed the same way as print #1.

 

Just a thought.....

John

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Thank you @JohnInOttawa. I also thought it was the humidity at first so I bake-dried and sealed with desiccant, etc.

But I think it's interesting that my PVA stops extruding at the same height regardless of the print size. (I have a larger print that also failed to extrude PVA at a nearly the same height level.) So now I'm thinking it might be Cura related?

 

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Here is what solved my problem. Storing it properly is only a first step of solving the issue. If it is getting wonky at the same height, you are getting that much moisture into the PVA during your printing. Starts out good and then gets all lacy and unsupportive at the same height, I would say it is the moisture attacking it at the printing stage.

 

For me, I do not load my filament on the back spool holders. I got a polybox for all my printers. This keeps the PVA going much, much longer. Just remember that even though it is in a drybox made to print from, with a bowden tube no less, it is still not an airtight solution. There are still gaps between the tube and the loading port on the feeder. And, the Polybox is not hermetically sealed. But it does have a ton of desiccant in it that I can recharge when the colour changes. And, it greatly, greatly extends the life of the PVA before having to dry it back out. Of course, I go through the stuff so fast with my prints, my purchasing of PVA and that expense is now my issue.

 

When I get a very, very humid series of days, it can still cut down on the time it works well.

 

But, this is not a Cura issue as I have seen what is in your pictures on my system, and it is always humidity related. I did find a way to do hot pulls in the middle of a print though and this link explains it:

 

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