First long print (35 hours) PETG stringy and gaps in print

I could use a little help troubleshooting this print. I don’t have enough experience on whether this is a temp issue, nozzle size, etc…

I have seen much better prints but don’t know the adjustments to make…

Using .2 mm layer thickness, .4 nozzle size, 220 nozzle temp and 70 degree PEI textured plate.

Thoughts?


Thanks,
Craig

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1.)220 for PETG is 35 Degrees to Low 255 IS minimal!!!
Get that Up and retry!!!

2.)With 220 you nearly have No Layer-Adhäsion and the material-flow is to Low

Just use the unmodified ‘Generic PETG’-Profile

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I suspected this to be the case…i am working my way up in temperature, but slowly. Here is the info label, and I am still building experience to know whether to override the manufacturer’s suggestion…


Thanks for your response and input! I really appreciate you taking the time and I’m trying out your advise!

This “Info-Label” is ■■■■ as usual.
go to 255 directly. dont take tests, just do it :slight_smile:

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220C is definitely low, but may not be everything. I do agree with Lucyna though, start at a normal temp and see where you end up.

PETG is not an easy to print material as many people think. Its sensitive to moisture, requires high temps, strings easily, and it can stick too well causing issues releasing from the bed and as well sticking to things it shouldn’t stick to like nozzles (which causes collisions).

Personally, I’d suggest doing some tests with a MUCH smaller scaled done model. Scale it down to 25% and try it again, that was if it fails you know fast and can test fixes fast. Instead of scaling you can also cut it down to just the middle portion, again the idea is to use less of the model as a test before running the full model.

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Hi Craig

I had great results using the Bambu PETG, I prep my Engineering plate with SOAP and IPA, and the Temp is 270C and 80C on the Bed on the X1C.
by the way, You need to dry the spool from moisture, I did the 8h preset from the X1c dry filament option. Without these steps inspect failure which I witness the hard way!

This lampshade was broken so I used a Clear PETG to reproduce a new one. each section was a 5-hour job to produce a 20" in ODiam ring. and it came out perfect!


good luck!
Erol

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But I WANT it to be so easy! :wink:
Thanks for your response and help!

Thanks for the response! lampshade looks amazing…

If I look at your picture it seems that it was printing fine at first? I mean the first centimeter or so? Then it got ugly and then it fixed itself again???

If that is the case it might be a nozzle clog that cleared itself? Or a spool that got tangled up? If it printed fine at first it was not due to the printing temperature I would think.

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If the manufacturer says “220” then 220 is definitely not low.

There is no universal “PETG” formula (or any filament, for that matter). Manufacturers blend in their own “secret sauce” to try and get their filament to behave optimally. Or budget manufacturers don’t do any of this stuff. Every filament from every manufacturer is going to be at least a little different from the competition. If they bothered to print a temperature on the label, you have to assume they have data to go with it.

This looks like nothing more than soggy filament to me. I say that a lot, it’s my “go to”. But excess oozing and stringing and bad adhesion with a highly hydrophilic plastic like PETG is almost always moisture induced. When it isn’t, at least in my experience, it’s because it was just crappy filament.

I note that the problems with these prints occur in bands. That suggests that maybe the filament on one side of the spool absorbed more moisture than the other, so as the printer unspools filament it goes from a band that’s really wet to one that’s not quite so bad… if it was temperature, the issue would be occurring more “uniformly” throughout the entire print.

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Yeah, it sort of looks like that, but the higher nozzle temp is helping, it seems. considerably less stringy-ness and a little shinier. I am liking the change, but the label caught me off-guard

I’m following your reasoning, but the higher temp does seem to be laying out better. If it were a “banded” moisture issue, i would think it would be spread throughout the print randomly, and not in localized areas of the print, across multiple layers. I suspect that at the edges the temp is a bit lower than in the middle of a warm thermal mass, so it is more apparent and common at the edges. Those spots in the localized environment are just too cool for the material to behave as designed. Just a neophyte’s guess on my part.

Let me tell you after years of printing: 220 IS TO low.

240 minimal. Taking the needed FLOW of the Material with the Bambu speed into account → 255+

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I think the temps on the label are for “regular” printers like enders and pruca etc. As soon as you start printing faster like on a BBL X1C you need to increase the temp.

I usually stick to the BBL studio defaults and work from there.

Also slowing down the print might help a lot.

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The filament label says:

image

I agree, that’s an unusually low temperature for PETG. That must mean it’s formulated differently so it will melt well at this lower temperature. Otherwise, why would the manufacturer specify it so low? No one would get good results with their filament and after a while they wouldn’t be able to sell it.

Yeah, you need higher temps for higher speed. But looking at this print, there are no significant long straight sections. I would be surprised if the printer is accelerating hard enough to get anywhere near it’s actual max extrusion speed (which is limited by the volumetric flow parameter in the filament settings regardless of the speeds set in the slicer).

The slicer would of course provide this speed information. It would be informative to look and see if there are significant speed changes associated with those good/bad bands.

Hard to imagine how banding could be because the filament isn’t hot enough. You can clearly see areas where the filament printed beautifully for a while, immediately adjacent to areas where it didn’t print well at all for a while. The temperature shouldn’t be changing much if at all. Perhaps there’s an issue with the nozzle heater. But if not, temperature isn’t the reason for this. That’d make it likely it’s some repeating variation in some physical characteristic of specific areas of the filament.

Running hotter might clean up some of this. But heat’s not the root cause and it won’t fix it completely.

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Could definitely be more than the temp, but 210-230C for PETG is oddly low. It wouldn’t be the first time Amazon/Ebay filament had bad info on it. I couldn’t find a TDS for it so I can’t say one way or the other if the spec is correct.

My guess is the low temp is causing a partial clog or odd extrusion which is crashing the toolhead and causing the missed steps.

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For a print that large I would recommend using a rapid or high speed PETG filament. I have been using Elegoo Rapid PETG for large prints and getting good results with faster print times and very little stringing. I have had issues with the Elegoo filament getting stuck on the spool, the extruder just could not pull the filament off the spool. I think they wind it too tight. I now re-spool the filament, even though I am not using the AMS as my print requires all 4 corners of the build plate including the exclusion zone for the filament cutter.

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Quit messing about with small random changes. Use a temperature tower that will change the temp for each of multiple levels and then pick the level that works best. One tower will probably take less time than you spend on one failed print based on a guess. If the best value is at the very top or bottom, you may have found a better temperature, but not yet the best. Re-run the test with that value in the middle, but with maybe a smaller range. There are plenty of available temp tower models available.

Better yet, use OrcaSlicer, which has a temp tower and other necessary calibration tests built in. Then you can slice the model in a familiar interface with more options than Studio offers.

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As @lkraus said, print a temp tower and have the max at 265-270. Look for the best looking one, but then break it until you can’t anymore. then use two pairs of pliers and find the place where you cannot break it anymore. The plastic will stretch and twist but wont snap. For me this temp is around 255-260 degrees for PETG marked as 230-250. If I print PETG at lower temps then smack the part on a something hard it shatters worse than any PLA I’ve ever used. Going even lower with the temp will let me unravel the whole print as though it’s silk PLA printed in vase mode.

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Interesting thing you said… I’d like to use all of the need to machinist my printed board size, but the exclusion zones block that. How didn’t see how to override those to allow printing on the full bed size. Not using the AMS allows that?