VERY weak PETG prints using PLA as support material
Greetings,
I'm having issues printing with MK3S+/MMU3 (with 0.6 nozzle). Recently, I saw some Youtube videos using PLA as a support material for PETG prints (or vice versa), since they dont like to adhere to each other well. The idea sounded fantastic and most of the prints look great, but upon testing it and trying to print some parts I've run to the issue that PETG prints using PLA as support turn out VERY weak. I can easily tear them apart with my hands only, both the PLA support and the PETG part. Funny thing is, parts of the print with no support/tool changes seem to retain their normal strenght. I thought the issue could be with temperatures not correctly adjusting to filament being used, but I printed a test part while observing the printer behaviour, and it seems to be correctly heating and cooling down depending on the filament. In my example shown below, the bed temperature is of course a non-issue, since none of the support material touches the bed.
I have tried 0.30mm full soluble and soluble interface print settings to no avail, but of course using the soluble interface setting the weak points are alot smaller.
Otherwise the MMU performs normally and color changes are no problem, only the multimaterial tests I'm conducting are a problem.
Has anyone else run into this issue and what can I do about it? I've tried fiddling with the settings but I'm certainly not an expert in this field.
Attached you will find some photos of the parts, screenshots of settings used and previews in PrusaSlicer.
I'd appreciate any opinions in the matter.
RE: VERY weak PETG prints using PLA as support material
Good morning Ghost Buster,
It looks like the ghosts have grabbed your pictures because there are none attached to this post.
Your issue, is almost certainly due to insufficient purging between the material changes try increasing the purge volumes
consider using PLA as the interface layer and PETG everywhere else
try using a raft, to prevent PLA and PETG on the first layer
try considering the supports to be soluble (Even though they aren't)
change the setting all of the support filament settings to PETG (except the interface layers) to strengthen the supports (otherwise the supports end up as a mix of PLA and PETG making them weak) similarly use PETG for the perimeter of the Purge tower to help stop it delaminating.
below is an example of a possible setup
please note I am not able to test this as I am not at home, and not on my normal PC and My 69 year old memory is not as good as it used to be...
good luck,
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: VERY weak PETG prints using PLA as support material
Hi and thanks for the suggestions!
Weird, I was fiddling with the images in the "Add Media" and i can see them on the post on my end, maybe some "waiting for moderation" thing... I'll post them again.
I will try and increase the purge volume, great suggestion.
I will also try messing around with the "soluble interface" settings and see if that'll help.
RE: VERY weak PETG prints using PLA as support material
This time i used the soluble interface preset and upped the purging volumes to 200 mm3. I would upload the .3mf or gcode file here, but for some reason I'm not allowed to upload those type of files. I'll just upload some photos and screenshots instead. Interesting restriction for a 3D printing forum...
Vertically printed part turned out to be very weak on the layers where the interface PLA is also applied. Lower portion of the object pried apart when gently twisting the support structure to see how easily it removes. Parts where no material changes were necessary seem like normal strength including the middle portion of the object with PETG support structure. On the other hand, it's easy to see inside the parts and notice that there is no cross-contamination of materials inside the PETG structure or the PLA support interface layer.
Horizontally printed object was much stronger, but still nowhere near as durable as an object printed with normal supports. Lower half of the object was fairly easy to break with bare hands, retaining maybe 40% of the strength of the rest of the part.
I'm kind of at a loss here, I cant figure out what causes this. I hope someone here has some words of wisdom to offer, because i think the PLA/PETG support idea is fantastic and produces really neat-looking supported structures.
RE: VERY weak PETG prints using PLA as support material
The forum will not accept .3mf files unless you ZIP Compress them.
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: VERY weak PETG prints using PLA as support material
Oh, that makes sense, thanks!
test horizontal and vertical object soluble interface
RE: VERY weak PETG prints using PLA as support material
Ghostbuster, I am facing similar issues. Were you able to resolve yours? I'm using MK4S + MMU3.
It seems to me that the REAL issue (at least with me), is the amount of time it takes to switch filaments and purge the extruder.
I have tried playing with temperatures as well as cooling fan settings. It feels like the only solution might come from slowing the PETG print speed way down or to enclose my setup?
The underlying problem is purging. It's a problem we first saw years go with the first MMU and again with the MMU2.
Because both filaments are going through the same hot-end and nozzle there is the need to purge the old filament each time you switch to a new one; unless it is completely cleared the next extrusion will include a contaminating quantity of the old filament along with the new. This mixture of incompatible filaments is inherently weak.
It can be done but you need to purge *huge* amounts of filament, at the higher of the two print temperatures, at every change.
If you are only printing two colours of the same plastic the purge can be very much less, just enough for cosmetic acceptability.
Unless the print is unusually important it isn't really worth attempting true multi-material with the MMU and a single nozzle but with the multi-toolhead XL for example, it is straightforward.
Cheerio,
RE: VERY weak PETG prints using PLA as support material
Hi,
@JGeiger2024 No luck, kinda gave up on it.
@Diem Thanks for replying! This is what I myself suspected, because there really is no other explanation. Except maybe for some kind of a bug in the software, mixing up temperatures, purging or some such thing (didn't notice anything like it though).
I tried adding more purging, but if it's like you said that I need way more, then it's not worth it just for cleaner support removal.
I've been drooling over some >400 m^3 printers with either IDEX or multi-tool, but Ratrig V-Core 4 has had mixed reactions and it's a costly gamble... Perhaps I need to wait for the new multi-tool systems announced this year to hit the markets.
Cheers!