PVA Spool issues

[dimberman 0]

Hello,

 

We have an Ultimaker S5 at my office, usually we print PLA or TPU and use PVA for support. We've been noticing that as the PVA spool gets low, the material starts to jam and the feeder grinds the material down. Our guess is that the material is wound tighter towards the end of the spool and is causing the feeder motor to work harder to move the filament through the bowden tube, causing it to fail. Attached are images of the spools when we've had to replace them plus pics of our dry boxes & storage. Guessing humidity is not the culprit here so we're wondering if anyone has had a similar issue and if there are any resolutions.

 

Thanks!

 

 

[gr5 2,172]

It might still be humidity.  At least for me personally, I've found 25% is still much too humid.  I am now getting it down to about 15-18% and I'm not sure if that's enough or not.  I end up drying the filament so often even when it is stored at 18% humidity but not sure if I need to.  I use a cup (1/4 liter) of desiccant per spool and I recharge the desiccant about once per month as even in a zip lock there seems to be small leaks.  Or maybe the desiccant is just slowly removing moisture from the newly exposed filaments over many weeks.

 

A better test is to look at the color of the printed material.  The bottom layer should be very difficult to see - transparent.  Higher layers should not be snowy (which implies tiny bubbles) but somewhat transparent.

[gr5 2,172]

So have you recently tried a new spool?  If it also has trouble then  I would do hot and cold pulls of your PVA in the BB core.  The tip of the nozzle - just inside the nozzle - the narrowest part - can get caramelized PVA build up on the inner surface.  Doing 10 or so cold pulls should clean that up.  This reduces the diameter of the hole in the nozzle when you get buildup like this.

[dimberman 0]

Hi gr5, thanks for the reply & tips. We'll try decreasing the humidity further and report how it goes. 

 

Usually the new spools work just fine, which may indicate that it is in fact a humidity issue.

[gr5 2,172]

Well again, there are clues if you see steam coming out of the nozzle when you load the filament or if you hear crackling/popping of boiling water or if you see a snowy like look to the PVA versus more transparent (this is tougher to describe).  I always have a *little* steam so it's hard to say how much is okay.  

 

By the way, if the PVA gets too dry it gets brittle.  I'm told.  I assume that is around 10% humidity.  Not sure.  I've never had that problem.