What could be causing this?

[GAD 9]

This is an Ultimaker S5 Pro Bundle (though it wasn't ordered that way).

 

The black filament is Ultimaker Tough-PLA, and the blue is MatterHackers PLA-Pro.

Settings are default Cura "Normal" 0.15mm layer height. 

 

The stringing (if that's what it is) is only in the direction of the Print Core Switch. In other words it only seems to be happening when the printhead moves to switch between colors. The rest of the print is nice and smooth. The stringing is happening with both colors/materials and appears to be happening both on the inside and the outside of the object, which is a "dragon egg" that's hollow. Actually looking at the second pic I can see one string on the left side, but on the last one of these I printed the entire thing is smooth except for about a 45-degree arc. 

. 

This does not happen at all on single-color prints. I haven't noticed it on PLA/PVA prints, but then PVA is usually pretty messy anyway and the PLA would be encased in the PVA most times I've done that. 

 

Any ideas?

 

Edited November 4, 2021 by GAD

[tinkergnome 926]

17 hours ago, GAD said:

Any ideas?

 

I would try one of these two options:

 

• use a prime tower (should be the default inCura, but i don't see one in your pictures) - and position it close to the "stringy" area
• as an alternative: enable the ooze shield

The intention is to "capture" any material that oozed out during the nozzle switch - so that it doesn't end up on the actual object.

 

[geert_2 556]

These are "insect antennas": the nozzle is leaking a bit when traveling through air. Upon reaching the next object, that drop is deposited on the side of the model. The next layer, the drop is deposited on the previous drop, sticking out a bit more. And so on, causing these nice insect antennas.

 

[GAD 9]

Thanks, all. 

 

I hate prime towers because they're wasteful and my other 2-color prints haven't needed them, but they've all be short and squat. I tried one last night and it was a disaster.  I have no idea what happened since I don't usually have adhesion problems, but I'll give it another go.