PVA Breaking in Feeder

[PAFablab 0]

While observing my print I noticed that my extruder 2, which holds PVA, continues to "print", but nothing is coming out. All the while Extruder 1 is printing just fine. I begin to think it was a tiny glitch and that the print would self correct, but the PVA material completely stopped extruding even though the Bowden tubes were full of the material. After ending the print I realized that the PVA material broke inside of the feeder which is strange because it had never done that with my previous prints. Can anyone explain why this is happening?  

[whoneyc 10]

Did the break have a grinding spot?  We have been going over similar issues in my thread here:

 

 

 

[gr5 2,181]

Well don't let the PVA stay hot in the nozzle for more than 10 minutes or it tends to bake itself into a semi permanent gunk.  You need to do repeated hot and cold pulls (do it from the UM3 menu) to get that core cleaned out again.

 

Not sure what the original cause of your grinding would be but if the filament is too dry it will be brittle (break off the end at the end of the spool to test it) and if it gets too wet then it boils and pops and snaps and I could imagine maybe it can't keep up with demand (too much pressure in nozzle) and would grind to dust back in the feeder.

 

Try to keep the filament in the bag with the dessicant whenever you aren't using PVA or Nylon.  other filaments aren't so sensitive to humidity.

 

[Dim3nsioneer 557]

I recently had that effect of broken PVA too. It actually broke at insertion (when the feeder loads it). Interestingly everything was fine when I cut off the part that was inside the Bowden tube. The room which this happened in was also rather on the dry side.

[Kvanwem 2]

On my S3, the PVA constantly breaks at the feeder. It is extremely brittle and I've had it actually break when trying to take out the natural curl when loading it.

 

Running a simple print today and it has broken 3 times inside of 15 minutes. 

I have heard that it "Dry's Out" , which I find curious since it is recommended that it be kept in a humidity free environment so it doesn't absorb moisture.

 

You can see where it is actually cracked in the center of the tube...

[Smithy 1,144]

If it has absorbed too much moisture then it gets soft and sticky, but too dry is also to the best way to store it. I store it at 25-30% in a box with some silica gel packs.

[Kvanwem 2]

I live in AZ so my humidity is 22-30% typically (indoors). I also store my filaments in a vacuum sealed bag  with desiccant, similar to how they come from Ultamaker. It seems that the PVA dries out naturally (the spool is about a year old). 

 

The PVA is now so brittle that it breaks at the feeder due to feed roller pressure when adjusted to center point as recommended, as soon as the tension lever is closed, the PVA snaps. I backed it off to minimum pressure, which helped a bit , but is is still happening. I can hear the "Snap" from 12' away across the room. It has taken 2 days to do a 1 hour print (about 10 prints aborted because on "Resume" the #2 print head resumes .5" off center and destroys the partial print).

 

I need to figure out how to get some moisture back into the PVA to make it more pliable so it doesn't snap.

 

When I bought this printer it sounded like a great idea, to me this is a case of over promised and under delivered (as far as the PVA is concerned). I have 4/5 of a spool that will have to be discarded ($50 wasted).