Trouble Extruding PVA (Solved)

I've been printing with PVA for a little over a week now, and initially it was printing quite well. For the past two days however, I haven't been able to get it to extrude consistently. It will work for a little while, and then the filament will just bunch up between the hobbed bold and the hot end. I think the material has absorbed too much humidity from the air and is now just too soft to support the force of it pushing itself through the hot end. Last night I tried drying the roll in an oven at 60C for 12 hours. When I tried printing with this dried roll, it worked well for a little while and then started crapping out again (maybe the middle of the roll didn't get dried)?

Has anyone else had issues like this with PVA? Anyone have any suggestions for something I haven't tried yet?

I went ahead and ordered a few individually wrapped 0.25 lb rolls from Protoparadigm... hopefully that will fix the issue.

Thanks for any input!

Edited 1 time(s). Last edit at 05/16/2012 01:21PM by gtg252b.

If it is kinking between the hobbed bolt and hotend does this mean you have a gap? Or maybe you are using an extruder designed for 3mm filament with 1.75mm filament?

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There is a very minimal gap... I've not seen any extruder designs that completely eliminate this. The extruder is designed for 3mm filament, but my hot end is for 1.75, and I've never had a problem before. I think that having the smaller hole getting down to the hot end would only increase the force required to push the filament through, and would make the problem worse (but maybe I'm thinking about it wrong). The printer still prints PLA and ABS perfectly.

could that not be heat getting up to the top of the filament making it weak and the the bolt bending the filament beacuse its soft?

try running a fan?

I've got a fan on there currently, and I've had zero issues with PLA or ABS. I really think that this is just an issue with PVA being very susceptible to humidity. I just got my new rolls of PVA in. I'll report back on how they work out.

As a side note, I'm really impressed with these PVA rolls from protoparadigm. They're individually sealed with desiccant, and they included a few zip-lock bags with extra desiccant in them.

Arghhhh, I'm still having the same issue with the new PVA. This is driving me nuts! I can't figure out why it worked so well previously, but stinks now.

OK, I figured it out. It was definitely a humidity issue. The PVA just sucks the moisture out of the air and then gets too soft to extrude nicely. The new material I ordered came with the problem. Protoparadigm thinks that the package ruptured in shipping because of the pressure changes in air shipping (I had ordered it expedited). I was able to dry the PVA out by putting it in the oven at 75C for 8 hours, and it printed beautifully after that. My previous attempt at 60C for 8 hours must not have been hot enough.