[Trouble Printing with PVA]

It is generally not wise to experiment with the settings. Stay away from speed, flow, extruder temperature and bed temperature, since the default settings in Cura are chosen carefully by the printing specialists at UM.

Your PVA looks underextruded, meaning less plastic than planned leaves the nozzle.

Ambient moisture is a likely cause. Did this already happen with the first print right out of the bag?

I like tweaking with the settings just because everyone's environment is different. Honestly, I find myself back at the default settings more often then not, but I'm a "learn-by-doing" kinda guy.

And no, right out of the box the PVA did pretty well. But to be fair, the early prints I did were not very complex and didn't use that much PVA.

It sounds like humidity is a pretty consistent answer across the board. I'll try some techniques for drying it out (and keeping it dry).

[Trouble Printing with PVA]

As you say the problem has gotten worse as time goes on, it may be absorbing more and more humidity. Follow gr5's advice. I was having some issues, and I usually have none to really speak of with PVA, and he pointed out a thing or two related to the humidity and temp and it was the problem.

Also, what is your bed Temp?

What are you using to adhere the material to the buildplate with?

My bed temp is 60 degrees C and I'm using the glue stick provided with the printer for adhesion. Actually, the stick is almost out. Any suggestions for replacements?

[Trouble Printing with PVA]

Well if the pva doesn't stick to the glass then that's a different problem and easily fixed.  But I'm guessing from the photos that the main problem is humidity.  That was my thought before I read any of your text.  Do you have an electric oven you can use to dry the PVA in?  First find the softening temp of PVA.  it's quite cool - maybe 50C?  I truly forget, sorry.  Don't let the oven get over that temp.  Put the PVA in for a few hours.  

Then when you are done printing with it make sure you put it in a sealed bag with dessicant.  Buy some of that rechargable dessicant that you can heat or microwave back to dry again and redry the dessicant when it changes color per directions.

Hmm, I'm sure I could rig something up in the fab shop. Do you suggest re-heating if there are long periods of time between prints? I've only used about 50% of the 4kg roll thus far in 2ish months.

[Trouble Printing with PVA]

My engineering team just recently purchased an Ultimaker 3+ and I'm running into some issues printing PVA.

A lot of times the PVA is dragged across the print area, leading to support failures by the time the first layer of "real" material is printed on top. This usually occurs after a few good layers of printing, and the situation worsens as more layers are added.

I've already increased retraction distances and avoid printed parts when travelling. I've also lowered the print temperature of the PVA to help mitigate some of the oozing when the core isn't being used. Additionally, I've tried the Prime Tower and slower print speeds/printing jerks, but I see no noticeable improvement.

Now the humidity in the office fluctuates pretty badly, so that could be contributing, but I don't hear too many "pops" when the PVA is extruding. The situation seems to be getting slightly worse as time goes on.

In my most recent print, the PVA structure got very tangled, causing the Nylon layers to be pretty terrible at those interaction points.

Attached are a few pictures of the tangled mess. Usually it's not this bad. I'm monitoring the temperature inside with a thermocouple and that seems to be pretty consistent. This occurs with PLA and with Nylon.