Problem altitude PVA

[herve_sthioul 0]

I have a dual print with PVA and PLA. After a few layers the PVA is almost 1mm higher. Therefore. the PLA nozzle touches and tears off the material.
I use : Ultimaker 3-extended / printcore 0.8mm / Cura with standard parameters

Before, all print was allright and sudently it's bad.

[gr5 2,170]

90% chance the problem is humidity.  PVA absorbs water very quickly.  Just 24 hours in a 60% humidity can be enough to cause problems.  Probably why Ultimaker invented the air handler and material station.

 

Loosen the spool a bit (so air can get at deeper coils) and put the spool on the UM3 heated bed and set to 70C and put at least 200mm of blankets or towels over it.  Leave it like this for 10-30 hours.  Don't go hotter than 70C or you risk ruining the filament.  If you are in a rush and only need a few meters, you can unspool 1 to 5 meters of filament and put it on the bed directly with the spool on top.  Still cover with towels but now you only need to heat for maybe 6 hours.

 

After you have dried your PVA, buy some extra large packs of silica.  I bought a gallon of color-changing dessicant.  I put the dessicant in containers with holes in them and when the dessicant changes color I put in a bowl and microwave until back to the dry color.

 

The dessicant container I put in 2 gallon zip locks with up to 2 spools at a time.

[herve_sthioul 0]

I would be surprised if it was just humidity. I have been using PVA for at least 3 years with 0.4mm nozzles and we did 3 pieces last week with no issue with the 0.8 one. The weather is not particularly humid.
The only possible explanation would be that the coil was contaminated with the Covid-19, very activ in Geneva. 🤒
Could a setting in Cura be responsible?

[gr5 2,170]

pva tends to get contaminated on the outer layer first so maybe you just printed larger/faster before?

 

Well it could be the leveling.  Do you do manual or auto leveling?  I recommend manual.  Maybe something was on the print bed where it levelled the 2 nozzles.  Or something on the end of the nozzle. But normally it shouldn't matter as it will heat the nozzles before active levelling.

 

And if the leveling is off between left and right core then you should also see issues on the bottom layer.  If PVA nozzle is  off by 0.5mm (a lot!) then the bottom layer wouldn't even stick.  No I suspect it's humidity.  Try a fresh spool or try drying this one.

 

When it prints the bottom layer of PVA it should be transparent if it's very dry.

 

Please show a photo part way through the print when the pva is "high".