PETG with PLA support interface layer - failures?
Hey all,
So I inherited a Prusa XL at work to print with, which is my first Prusa experience.
I have 2 Vorons and a BBL A1 mini at home.
Because it is mostly used for research, it is an offline printer. This mainly means that my ability to babysit a print is very low.
I also can't sit next to it for the first 9 hours, due to other work responsibilities.
I have this print I need to make for work, which needs a very smooth finish on a large bridge.
I've done tests at home with a PLA interface layer on top of the support, to print the PETG with 0 z-distance between support and the bridge that needs this perfect finish. The support starts on the bed by the way. Due to temp differences in bed-adhesion it has to be mostly PETG supp with only the interface layer being PLA.
I did tests at home on my own printer with AMS/Filament changer. This created the smoothest bridging I had ever seen and this made me very happy.
However, when I tried to implement it on the work printer (PrusaXL with 2 toolheads, where I have to print it on, because of very strict rules) the print failed.
Note: I used the same filament spools for both the test at home as the print at work. Both times I pre-dried the PETG for 6 hours in a filament dryer.
For some reason on the XL it seems like the PLA support interface layer does not adhere to the PETG at all. On both my Voron 2.4 as well as my A1 mini this was not a problem at all.
I think this is mostly my own fault that probably lies somewhere in the slicer settings, as I am not experienced with prusa-slicer whatsoever. |
I've added some printscreens with my settings below.
My best guess is maybe the bottom fill pattern (Hilbert Curve) is too much for a XL at the PLA/PETG intersection.
I just can't believe that I tuned in my voron better then this XL is, since it was no problem with my test at home.
So I figured I'd ask you guys for some input.
Thanks in advance
RE: PETG with PLA support interface layer - failures?
That's been my experience too that PLA just slides off the PETG supports (and vice versa). It seems a bit model dependent, basically how much contact surface there is. Just surprised why it worked on your Voron. Curious what others have to say.
Formerly known on this forum as @fuchsr -- until all hell broke loose with the forum software...
RE:
May I Humbly suggest that you tell lies, to Prusa Slicer.
Prusa slicer will not accept normal PLA as an interface material on the purge tower. so.... Tell Prusa slicer that you have Soluble PLA... (Yep I know it's not common!)
Choose an XL printer profile with Soluble interface
go to the 'Filament settings> Advanced> Filament Properties' tab and tell slicer that your PLA is Soluble...
then go to the 'Print settings> Multiple Extruders > Extruders' tab and set 'support material/raft interface extruder ' to point to your PLA extruder (extruder 2 in this case), and make sure that your Purge tower is enabled 
The model in this image was turned in its head juts for demonstration
As you can see, there is a thin PLA interface layer between the PETG Supports and the m0del
regards Joan
I try to make safe suggestions,You should understand the context and ensure you are happy that they are safe before attempting to apply my suggestions, what you do, is YOUR responsibility. Location Halifax UK
RE:
Posted by: @joantabb
As you can see, there is a thin PLA interface layer between the PETG Supports and the m0del
regards Joan
I do get the interface layer as PLA, did not have the check of "soluble material" in the extruder settings. Will try a test soon to see if that makes a difference.
When I print this piece, it is like the PLA layer is almost entirely scraped off when changing to the PETG again. Some of the PLA does seem to stick between the print and support, but the first layer of PETG looks horrible.
That's been my experience too that PLA just slides off the PETG supports (and vice versa). It seems a bit model dependent, basically how much contact surface there is. Just surprised why it worked on your Voron. Curious what others have to say.
I cannot tell you what I did to make that work.
It was the exact same test-piece I tried to print.
Same 1 layer interface made out of PLA. Even the same spools of PETG and PLA.
I did slice with Bambu Studio (normally use superslic3r for my Voron, but that version didnt support multi material supp).
Too bad Bambu Studio doesnt support the XL, so I can't test if it's a slicer difference for that regard.
RE:
I don't have time to explain it all, but I've had great success by modeling your own supports, including the interface layer at 1mm thick, making sure they stay separate bodies. The 1mm thick is necessary because if the 1st interface layer doesn't stick that great, the other layers will.
Then in the slicer split your model into parts and make your interface layer part all perimeters. I've found that the back and forth motion of solid infill is more likely to peel up the pla vs. going the same direction as it does with perimeters.
You can setup your support material part with only 2 perimeters, 15 or 20% infill with no top layers to help the pla grab the petg.
You also need to create a pla profile changing the bed temperature to your PETG bed temp.
I do what I listed above all the time and it always works.
Side note: You may be able to get PS to do what I'm telling you to do, but I've not tried to do so. I'm usually not impressed with the auto generated supports and often design my own to minimize waste and print time. PS it's really only able to create blocks of support, which is often not needed.
RE: PETG with PLA support interface layer - failures?
Here's an example I did. Hard to tell from the video, but you can see that the white PLA was all perimeters.
RE: PETG with PLA support interface layer - failures?
Makes sense. I guess I can get the same effect by bumping the number of top interface layers up to 30 or so but I see why modeling it explicitly is more versatile.
Formerly known on this forum as @fuchsr -- until all hell broke loose with the forum software...
RE: PETG with PLA support interface layer - failures?
You can setup your support material part with only 2 perimeters, 15 or 20% infill with no top layers to help the pla grab the petg.
You also need to create a pla profile changing the bed temperature to your PETG bed temp.
I do what I listed above all the time and it always works.
Thanks for trying to explain your process and attaching a video. The video is exactly the result I am trying to achieve.
I will try your method as soon as I've had the time for it and I will post an update here after.