My thought is to use Support for PLA/PETG as an interface layer on top of supports to get a clean print. However, try as I might, the PETG seems to blob up and not really adhere to the support interface layer. Subsequent layers seem to try to smooth things out, but the damage is already done (see the green).
Alternatively I also tried printing using supports without an interface layer and a larger z-gap between the support and the print material, but that ended being even worse. (I stopped this print before it got to the golden lettering.)
Any ideas on what one can do to get a smooth PETG layer on supported overhangs? Thanks for any suggestions! (I’ve been trying so many different things over the last 3 weeks, I’m at the point of giving up on the idea for this coin).
Comment on solution: what ended up being crucial for success were adaptive layer heights.
Use Generic PETG settings. In particular Bambu PETG Basic default settings are rather bad.
Next, use adaptive layer height to counter PETG curling at overhangs and set Top distance and Top spacing to 0 with a non-crossing infill pattern (like concentric) as PETG loves to stick to the nozzle.
Finally, if you still observe PETG curling, try to dry it thoroughly. Used only as a support material, I have found that to rarely be neccessary. But sometimes,…
Sorry, I may have misread. Using PETG with PLA interface?
In that case, dry the PETG first, then use/copy over Generic PETG settings (see the differences?), reduce all print speeds to below 100mm/s (a bit higher for HF), all print accellerations to 25%, avoid all crossing infill and surface patterns and enable wipe for retraction.
I forgot to mention that I dried the filaments for 16 hours prior to printing, so I’m fairly confident they are not moist. I did a trial print of a test model without overhangs or supports and that looked great.
I also ran all print speeds at 25mm/s to improve translucency.
I will try your recommendation and see if that helps.
It looks like you already implemented some of the most important changes (except cooling settings).
But since you mentioned transparency, did you follow high transparency recommendations like increased line width and increased nozzle temp?
Both of these have a negative effect on curling.
And for transparency you are probably using a 50% nozzle diameter layer height? Going lower is pretty effective at reducing curling.
It is a bit of a shame that anti-curling methods are pretty much the opposite of high transparency methods but then again, a perfect world would be boring
I have never had much luck with the “Support” filaments. I had great success with BVOH (after a lot of cursing dialing it in), in particular with PLA but also PETG.
But then I found the PETG for PLA support (and vice versa) thread here in the forum. Tried it out and never looked back.
I tried that approach as well, but I found that to have the worst curling. Using PLA as the interface layer resulted in no adhesion at all.
I think my issue is exasperated by using concentric patterns on all layers, which can be problematic for depositing filament on supports that have little adhesion.
Yeah, the concentric pattern can become a bit messy. But with 0 Top distance, Top spacing and adaptive layer height, I have found the default pattern to work pretty much every time for PLA prints with PETG as the interface.
I’ll post a detailed update in the morning, but looking at the print so far, it looks to be progressing MUCH cleaner. I’ll have to see how the layers print separates from the interface layer once it cools down, that’s always been tricky.
If your adjustment turn out to work well with the support filament, I will try it with PLA as an interface layer and see how that works.
This is at 0.1 layer height profile, but after turning on adaptive layer height, it changed it to 0.2 layer height in the slice.
I did try printing at 0.8 layer height without adaptive layers, and it turned out just as bad or worse than my original prints that globbed up on the green translucent layer.
The only other thing I would like to to eventually figure out would be how to get rid of the “track lines” on the translucent areas (green and red). I’ve tried so many different flow rates and was never able to get rid of it completely, thinking it might be something other than flow rate calibration?
And sorry for the confusion on adaptive layers. That was intended for the use of PETG as an interface layer rather than the coins.
As for the track lines, I am afraid that I do not believe rhat they can be eliminated fully. It may be possible to reduce their prominence by using a constant line width and matching surface patterns to keep them at the same location throughout the height. Also, they could become a feature depending on the surface pattern but I think the concentric pattern will be hard to beat. Finally, annealing under pressure may help a bit in this case but there’s a risk of going overboard for not much of a gain. Without flat plate pressure application, I’d expect some deformation from annealing. Work After Printing Finished (removing, cleaning, bonding the prints and cleaning the build plate) | Bambu Lab Wiki
