I had got things working nicely with PLA, tweaked various options, but I’m trying now with PETG-CF.
I’ve gone back to the default settings for PETG-CF, but I get these ugly bubbles appearing.
I dried the filament as per the instructions, prior to use.
Am I doing something wrong, or what do I need to adjust to make it look nice? Oddly, another object came out much better, so what is it about the structure of the thicker object that might be causing these bubbles to appear?
Does not look to bad, try to increase the infill density to get rid of the bumps in the middle of the first part. Maybe switching to something like line infill would also help.
Ironing should be better with a little more or less flow. Hard to tell from the images, but I would start with less and see what’s changing. Doing ironing with CF filaments is generally a bit harder. Calibrating the filament might also help, but judging by the pictures, that looks to be quite good already
I actually had it with ironing to begin with but it didn’t make any difference. But since the ironing and a few other settings had been tuned for PLA I decided to try with defaults.
The bubbles seem to be too big to be ironed :o)
I’ll try different infill settings, maybe it’s choosing different infill for the middle and outer portions.
it’s the hot air expanding under the top layer, try more infill or more top layers, a bit more cooling or lower temps for the upper layers too if that doesn’t solve it.
Increasing your top wall layers should help eliminate the bubbling as well. Make it 5 or 6.
I’d actually try that before increasing the infill.
PETG usually needs a higher flow rate to get better ironing results.
Try something like:
30mm/s speed
40 - 50% flow rate
.15 Line
That flow will be way too much for a good calibrated filament.
And going for 6 top surface layers will add more material than slightly more infill and also not fully getting rid of such heavy bulges. The line infill type will let any expanding air to travel through the part to avoid these issues.
I agree that adding top layers uses a little bit more filament (depending on the infill density setting), but not enough top layers will cause the infill pattern to translate to the top and that is one of things that looks like is happening in their print.
As far as the ironing, I am speaking from my own testing/calibration of PETG filaments. Your results may vary.
Here is the 3MF I use to test ironing flowrates:
I usually skip right to the 30 mm/s plate.
If there is something else I can do to improve it, please feel free to share… I am all ears.
True, but that mostly applies to prints where the bridges are falling down, I rarely see prints recover from these bulges in a reasonable amount of top layers.
That’s a nice calibration file, thanks for sharing!
Interesting to hear that you have to go that high for good ironing surfaces. I usually stay in the 10-20% range, even when going with Bambu’s PETG-CF wich is quite rough.
Only thing I would change in that test model is to go for 5% or even 2% steps. For me it’s usually 1 or 2% making the surface perfect.
In my testing:
PLA ironing range works best around 20-25% flow
PETG ironing works best around 35-45%
PETG-CF ironing works best around 45-55%
The caveat here is that line spacing is set to 0.15mm. I have not played with that variable and I imagine it could/would alter those percentages.
To be honest, I pulled the original ironing test off a printables and added some tweaks (labeling of the test pieces, changing the ironing directions) to make it a little better.
In my experience, most filaments have about 2-3 sections (10-15% range) in the test piece where the ironing “smoothness” is indistinguishable from each other. So incrementing by anything less than 5% seems superfluous.
But any one of those plates could be easily copied and modified to dial in the ironing in finer detail once the general desired ironing range is established.
Interesting. Are you using a bigger nozzle size?
The Ironed surfaces from the second image above looks pretty good already, but when you look closer at the smaller features, you can see some filament buildup.
That would make me belive lowering it would fix that.
My calibrations have all been with the .4 hardened nozzle.
As far as calibrating the filament, I only do a temp tower to find the best printing temp.
I used to do the 2 pass flow rate tests (with Orca) but it never seemed to make a big difference. Maybe changing (increasing?) the initial flow rate would lower those ironing ranges.
I will try some different settings - but I was curious as to why the second panel wasn’t having the same problem despite having similar thickness to the area where the first panel has bubbles.
I made this short video showing how the slicing varies between the two.
(with apologies for including the sound of the music playing at the time!)
The second panel aswell as being slightly thicker seems to also have a bridge layer that the first panel doesn’t.
Settings are identical for both objects, so it’s whatever the software has calculated.
Your link doesn’t seem to work.
That’s odd, I just pasted it into my mobile device on a different network (i.e. mobile, not my home network) and it works, so I don’t know why you don’t have access.
Early signs from the latest print are that increasing the infill density from the default 15 up to 25 has made a vast improvement.
Looking at the order in which it was printing, it does the infill for the non-middle sections and then they get a chance to cool down while it is busy fiddling about in the middle. Whereas, for the middle section it goes straight to the top layer after the infill which was when the bubbling was occurring. By the time it gets around to the non-middle sections to do the top layer surface I presume the infill has cooled down and thus no bubbles.
Increasing infill density of the middle section perhaps has the effect of making it take longer and thus more chance to cool down? I don’t know, just speculating. Seems like there ought to be a “proper” fix though, that tells it not to do the top layer of the middle section until the infill has cooled down?
So looking much better now having increased infill density to 25.
How about those artifacts near to the holes - is there anything I can do to improve things there?
My theory is that there where some bulging around the infill intersections due to the longer bridges of the top layer. But it’s hard to tell without observing the print; happy to hear that it worked out.
That looks pretty good. I guess you could look at the ironing layer’s order. The lighter sections seem to be printed earlier or later than everything around them.
Did you run the Flow dynamic compensation? Looks like it’s off by a bit. Sometimes, it’s hard to tell by the line method test, but switching to the pattern method can make it easier to see. And you should probably slow down the ironing speed.
I haven’t run any Flow dynamic compensation, I don’t yet understand when or how I would need to do that.
I will try slowing down the ironing to improve the appearance of the sections between the holes. When I print the same object using PLA the artifacts are a lot less noticeable.
How would I change the ironing’s order? I can only see options for the speed/flow etc of the ironing, nothing about the order.
