Hi! Looking for some advice here from friendly local experts.
I’ve printed this with Elegoo Neptune 3 Pro, 0.4 nozzle, Elegoo PETG filament, no enclosure. Using PrusaSlicer.
This print is basically all walls - the hex grid is thin. It’s 2mm thick and each segment is 1.5mm wide. I set 3 layers for walls in slicer. It was printed vertically, just as seen on picture.
The solid part of the print (back wall) came out just fine, but the hex grid part came… dirty. On the picture, there are a few hex segments that just broke off during the print at the base of vertical segments. And the rest of them have small loops of filament that stick outside of the intended surface, to the sides.
My suspicion is the print temperature is too low. I’m printing at 230, which is the low end of 230-260 range of the filament. But in my previous tests I noticed stringing that starts around 240, so I did a few other prints that were just fine at 230, and I made it my default temp for this spool.
Or is it just too fine detail for my printer with PETG? Or something else that I am missing?
It looks to me that more is going on here than just how dry the filament is. I see a lot of deformity on the underside of overhang structures which makes me think that the temp is actually too high for the speed that your printing at. I would guess as the plastic went down it was curling edges upwards into the height of the next layer and eventually the nozzle hit this plastic that was too high causing some damage. What speed are you printing at ? Petg likes to print real slow in my experience. Like 20mm/s or less gives it more time to cool. I go as slow as 5-10mm/s when I’m using a large nozzle, but with a .04 you can go faster. Lowering the nozzle temp will reduce the puddling and curling up effect.
I don’t dry filaments because I don’t care that much about things being perfect. If my plastic is going down goopy, I just turn down the nozzle temp until it isn’t… I’ve come to accept that things often print better if I set the print speeds to be slow. It gives the layers more time to cool before the nozzle comes back around.
All right, I think you are right on the curling upwards. I started another print, which is also using similar hexagonal sides, but is more massive - hexagons are larger, and walls are thicker. And it warps up visibly! When these overhanging arms on upper part of hexagons start printing, they just warp up while cooling. Then when nozzle comes back for the next layer, it hits the warped edges, pushing filament to the sides and making these artifacts. It didn’t break any segments, as they are thicker, but I bet that’s what happened in the original print.
On the new thicker print, the base of the model lifted up from the bed on one side at some point. I was watching the first two layers, so this happened some time later. Gonna try to slow down the print, lower nozzle temp a bit, bump up the bed temp a bit. Will see what happens.
That was my theory because of the damaged hexagons on your original print. Something was causing the plastic from the previous layer to be too high and the nozzle hit it while travelling.
You could also play with your travel settings. Combing may be undesirable on this type of print.
Maybe curling can be reduced by drying your filament, but I haven’t tried that. Curling seems to happen when the plastic stays molten for too long, often because it is going down too hot or because the nozzle is coming back around for the next layer before the previous layer has cooled enough.
Thanks for another interesting point. It is faster than you are suggesting. My slicer settings for “external perimeters” is 25 mm/s and for “perimeters” is 40 mm/s. There are no other type of movements on these hexagonal structures.
I may try slower printing at some point, but it’s already a 7 hour print 😄