I’m having an issue when switching from PETG to PLA (used for support interface).
PETG is being printed at 250, PLA (for interface) is 220.
I am printing the exhaust fan bracket and the default settings. When it switches from PETG to PLA, I start getting extruder overload error, it seems that the PLA is not able to flush the PETG.
My question is that shouldn’t it be able to do that as the flushing temp is usually higher than the set 220C for PLA? It seems it’s going from the 250C of PETG to 240 during flush but that should still be ok. I’ve tried to keep track but have not figured out what is going on. I’m pretty sure it was at the 240 temp when trying to flush PETG with the PLA. Twice now it’s done that.
Does everyone just set the PLA temp (when used as support interface) close to PETG temp so during swaps, the nozzle doesn’t cool below say 245? That means it’s also going to print the PLA interface layer at high 245 temp. Should that be ok?
I’ve tried to follow the PETG/PLA guide above on wiki but honestly, it lost me when it also started mixing in the comparison sheets for different materials.
In the “Comparison sheet for using Bambu PETG HF for the model and Bambu PLA Basic as support:” is it suggesting PLA temp at 245?
Also when looking at the opposite: “Comparison sheet for using Bambu PLA Basic for the model and Bambu PETG HF as support:”… it’s saying now the PETG temp should be 220? that makes no sense and seems too low for PETG…
what am I missing or doing wrong here to get extruder errors when it’s loading PLA and trying to flush out PETG.
FINAL QUESTION: I was able to complete the bracket by manual clearing it while on pause.. anyways it did what it was supposed to but the layer adhession of the PETG was TERRIBLE at the same layer it did the filament change to PLA. Bracket just separated into two at that layer, rest of PETG is strong. Almost as if when it switched from PLA back to PETG, it didn’t come up to 250 temp from 220 and just started printing WHILE it was heating up.
Comment on this part only – do you have set sufficient flushing when switching from PLA to PETG? check what the value is there – if it is low, PETG may be contaminated with PLA residue, and since these materials are incompatible, this will weaken the strength. Personally, when switching between PLA and PETG, I use a flush of around 800 or even 900 (and according to some sources, even this may not always be sufficient).
Ok this is making sense, thank you. I just used the default 1 multiplier and reviewed the purge, it’s not even CLOSE to your rec. It was only purging 139 when switching from PLA (white) to PETG (black). So doesn’t seem it was sufficient and the PETG had traces of PLA still which caused poor adhesion.
One thing I want to add it might shed more light on the overload.
When I took the hotend off while print was paused, I noticed that the end of the PLA where it would push the PETG (right at entry point of hotend), it had fanned out/slight buldge and that it was not even entering the hotend past maybe like 1mm, it seemed it was getting stuck there becuase the PLA had softened and instead of pushing the PETG, it was just compressing. This would happen if the PLA got too warm right as it entered the hotend, which would indicate possible heat creap? Is it possible that fins on the hotend were just too hot from printing the PETG at 250? I did feel that tiny fan pointing to the heatsink was blowing hard so I’m not sure how the heatsink would get so hot that it would soften the PLA as soon as it entered the hotend…. is that possible?
Just an addition from my experience with PLA x PETG printing (but I must emphasize that I am no expert… I’ve just had a few (dozen or two) successful and problem-free prints with this combo)…
If possible, I try to keep the temperature of both filaments as close and as low as possible – both in the nozzle and in the printer chamber (I have a P1S) … so even though the main print is from PETG (I normally have the printer covers closed), I keep at least the top open for such print. In addition, for such PLAxPETG prints, I use PETG from Devil Design, because it allows printing at lower temperatures than Bambu PETG HF. It seems obvious to me that if the temperature is too high, the PLA softens and has trouble passing through the nozzle (let alone push anything out).
I’m afraid I haven’t given you any specific, simple advice that would help, but in general… I would try to keep the temperature for printing PETG as low as possible (so that it still has some quality)… just because of PLA is involved. And maybe try to find materials that are closer in temperature… maybe some different PLA brand/type would accept higher temperatures than usual Bambu Basic (or so) and will be more suitable for this purpose.
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BTW, my only and completely crazy clog happened precisely because I forgot that I had PLA residue from the previous print (day before) in the nozzle, and I wanted to print ASA next day (I preheated the chamber for about 45 minutes … got approx. 62°C inside and then started printing… tried to start .. the PLA residue in the nozzle and extruder had obviously softened during that time, clogging everything it could, and I had a “great” afternoon trying to get it out.
I had this issue. The problem is heat creep. When you print PETG the chamber goes into heating mode. As chamber temperature rises, the PLA will soften as it enters the extruder.
Solution: Set softening temperature of petg to 45 degrees, so chamber will go into cooling mode instead of heating. Alternatively open the glass door
Thank you both for your responses. I think you both bring up good points and is likely contributing to the issue I’m having.
Basic PLA seems to have too low of softening point and heat creep is likely playing a role. The nozzle stays 250 for a bit while it’s loading PLA and the chamber temp also seems to climb quite a bit during PETG portion of the print. On top of that, the recommended bed temp is 65 in this use case for both PETG and PLA which is another contributor to heating up the chamber. While the AUX fan does go to 90%-100% during PLA portion, it’s not enough to exhause the accumulated heat from PETG portion of print.
With chamber in the 40s, the little hotend fan isn’t really going to do much blowing hot chamber air over 250C nozzle in the short duration it takes for PLA to make it to the hotend and I think that’s where the residual heat is enough to soften the PLA as it loads or tries to load. Then because the hotend now has to operate a lower temp it shuts down or lowers power and the softened deformed PLA is immediately hardened by the continuous air flow over the heatsink and by then it’s too late to push anything through.
This makes sense to me so I’m going to go with that. I’m going to have to combine the two suggestions and use PLA w/ higher softening point (I believe several PLA+/tough variants fall into this compared to basic PLA) and keep the temps as low as possible across the board.
Have you been able to successfully print PETG with PLA support? Are you using PLA as the entire support material or just a support interface separating PETG support and PETG part?
I have H2D with 2 nozzles and I wanted to use PLA as an interface layer instead of buying special filament “Support for PLA/PETG” for that. However, I couldn’t find any examples. Assuming the interface doesn’t touch the heatbed, would the chamber temperature affect PLA single layer interface so much?
I’ve done it with normal PLA just as an interface so yes just one layer.
I think the issue is that the PLA stays at the region just above the hotend and after a while starts expanding if the chamber temps are too hot. So you gotta manage the chamber temps
That makes sense, the softening temperature for PETG is 70 C, for PLA 45. However both have default chamber temp set to 0.
It turns out that bambu wiki has all the profiles under [Printing guide for using PLA Basic and PETG HF/PETG Baisc for support | Bambu Lab Wiki], including PLA support for PETG. It does say that the cooling settings for P2S are slightly different, therefore P2S has it’s own support profiles.
Just the interface layer, the colors are both black. I created a separate thread with as many details as possible to avoid over spamming this thread Hopefully I don’t bother OP. Any advice greatly appreciated. H2D - PETG does not adhere to PLA support
I found a workaround solution for this problem - you need to add 1-2mm PETG cylinder anchors for each corner, this keeps the lines straight and solves the problem.
Hopefully I don’t bother OP. Any advice greatly appreciated.