Yeah probably. But i don’t want to go higher as it gives too much waste for my taste.
not only too much waste, it also takes forever to complete the print. I still believe its not a good idea to decrease the flush less than 700 from PLA to PETG, as my prints get very very fragile with PETG, if I decrease the flush volumes. They break apart with very less force.
Update: The folloiwng below was better than my old settings, but after 50% my print fell apart again 
Okay, I think I nailed it:
- Main print material: PETG (bed temp 70 degrees, nozle temp: 230/230)
- Support Interface: PLA (bed temp: 60 degrees, nozle temp 220/220)
- Plate: Double Sided Textured Plate from Bambu Lab
- Noozle: 0.4 noozle with 20mm layer height
Important: I was not able to print without errors, before I changed the cooling to the following setup:
Support must be setup like this, if PLA is only used as support, but not as main material:
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How I just see this video yesterday !
But anyway it is always better to only use different material on interfaces supports only, lot less filament change, lot fasster
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False alarm:
My print was better than before, but after 50%, my print failed again and some layers fell apart
I am now trying the same temps for PLA as support interface for PETG. Both noozle temps to 230. Hopefully this time I run better.
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Thank you for this writeup, its great. Im loving this idea. I tried to do this for a PLA print and it worked great, but on the layers where its printing PETG as an interface layer, its also printing the infill as PETG. I have “flush into infill” turned off. Can you think of why this might be happening?
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Holy cow… your settings works amazing. The PETG popped off like nothing and gave me a very clean print. The purging was a bit wasteful, but the output was amazing.
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Just another datapoint on use of Bambu PLA layers for the support interface to Bambu PET-G parts. I print engineering parts on an X1 Carbon. I initially had amazing results for part quality when built using the Bambu Slicer settings advocated here. But I then found rapid nozzle blocking failures, sometimes only obtaining a single large part before encountering this. I assume the most likely cause is deterioration of the PLA in the nozzel due to excessive temperature.
The PLA prints at 220C nozzle temperature and the PET-G at 255C, which are the Bambu default settings so far as I know. I use 300 as the flushing volume between these materials, bidirectionally. I experience no cohesion problems with the PET-G parts, bed adhesion is good (enough) on my PEI bed using Bambu liquid gluestick, and support separation is very easy. The only problems are this nozzle blocking and occasional buildup of melted resin on the underside of the sock. Consequently, the machine needs light supervision, which doesnt work for my use-cases.
If anyone reading this has experienced and overcome these issues I’d very much appreciate your comments.
TonyO
I spent a significant amount of time testing it; unfortunately I am no Youtuber so I can’t give any nice fun video of the results.
TL;DR - the loss in strength is so serious that someone may need to write different filament changing g-code to ensure that the nozzle is absolutely, totally clean of any PETG before printing PLA, and the other way around. (flush more than 999mm^3, maybe wipe the nozzle a few times in-between)
I am fairly certain most people were not doing any serious strength testing on their parts, or their parts were overdesigned so the part strength near the support interface layer was not critical. The amount of strength loss due to PETG in PLA is extreme - I’m pretty sure it’s at least 2x-3x less, EVEN with nearly a 999 mm^3 flush. You are fine doing this for cosmetic parts, but if it has to be strong, this results in a serious loss in strength. Given how much testing I’ve done, I think it’s mostly a matter of everyone who says “it works” simply can take the loss in strength in the models they’ve tried (I’ve gone through kgs trying to tune various combinations). A similar effect happens with normally supported materials like Support W, but the flush volume before there’s no noticeable loss is much smaller - more like 600-800mm^3 was sufficient to prevent a serious loss in strength.
I’ll tell you the support test model I was doing - Support Test Piece With Support Floor Option by Fotmers - Thingiverse. Try printing that with normal single material supports, and make sure you have at least 5 top layers and 4 wall loops so that the overhang part on top is as strong as possible. Try breaking off the wall from the base. With no PETG support contamination (normal supports), I needed two pliers to break the wall off the base (so I get the base support test geometry + T that comes off). If your material and process are well tuned, you probably won’t even get a clean break along the layers. With PETG support, even at 999cm^3, the T basically came off with a minimal amount of force by hand, with a very clean break along the layer that had the material switch. I was using white/black for visual contrast, but it takes a lot more than visual flushing before the mechanical strength is back to normal.
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You could be right, but I actually print PLA at 240C as I’ve found it consistently results in better layer adhesion for the PLA I’m using. I remember bumping up and down the two temperatures and I saw little to no improvement in the loss in strength. I suspect it’s primarily the contamination issue.
The other thing I noticed while testing prints which further makes it difficult for this support combination to work was that PETG sometimes sticks on the nozzle and doesn’t get sufficiently cleaned up by the nozzle wiper, resulting in random PETG contamination throughout the print (if you do white on black you see it occasionally and it’s quite obvious). Even if you could flush the nozzle well enough with more complex g-code, this occasional contamination could result in some serious issues throughout an engineering grade part.
I also suspect that while printing PLA on the PETG interface or the other way around, the nozzle inevitably wipes on the other material and results in a bit of cross contamination.
If you read forums and posts from other older, more expensive IDEX systems, it’ll become pretty clear that cross-contamination related strength loss is a well known problem with multi-material support printing.
FYI, I basically ended up deciding to stick with Support W for breakaway. The inconsistent performance, complexity, and likely need to purge even more material than the single nozzle setup requires was likely never going to end up being a great solution.
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Thanks for the remarks. I will switch a part from PLA support to Support W with a fresh nozzle and compare nozzle longevity. I will also review the flushing settings I’m using and ensure I havent broken any of them in my experimentation.
Tony O
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So useful! Thank you!
I wonder whether the issue of using PLA as support for PETG has to do with too much cooling of the PETG layer while all the filament changes happen and not so much with contamination. See Major interlayer strength differences when multi-material printing - #3 by 3dsurfr
Does anyone have an idea for a good support interface for ASA prints?
I change all these parameters but it is objected to the PETG temp
“Error
Plate1:cool Plate is not suggested for use printing
Filament 2 (Bambu PETG Basic). If you still want to do
this print job, please set this filament’s bed temperature
To a number that is not zero.”
Does this sound right? I’m a BS newbie so looking for bed temp.
I’ve been doing some testing with that over the weekend and getting good results.
I have the same issue when using the support material. I think it is not enough flushing. The two materials are still mixed and not alowing a good bound at the layer were the filament change happened.
Probably. That’s what crossed my mind now. You can enter it manually. However, there is a maximum value. At the beginning, I experimented with very high flush values and the results were pretty good. But that produces a lot of waste.
Only when it works, as I have seen for myself on my printed objects, it is really very very good, the surface on the support material is then almost good as the surface of the print.
When using PETG as support for PLA I am continuously getting a clog in the extruder. I have the flush volumes set to 800 between the 2 materials. Any advice?
Open the printer, the temperature differences …
Does the clogging occur when the filament is changed?