PETG-CF Solid Infill/Top layer tearing on larger prints

[kragghc]

Hello!
I am quite new to 3D Printing, and am having a lot of trouble doing larger prints with Bambu PETG-CF on the P1P.

It prints pretty much perfectly, up until it reaches the top layers, where solid infill begins.
I’ve dried the filament for well over 12 hours, tried multiple different profiles, calibrated the filament through OrcaSlicer, looked at forums for similar issues and tried their profiles (Rom3oDelta7, 3DTech, wiremeup), increased/decreased Nozzle Temp, cooling fan adjustments, and more.

It can print smaller prints perfectly, overhangs and all, looks super good, no filament oozing or buildup as I can see during printing either (even on the big failed prints).
The nozzle did clog at one point, but I cleaned it out and did a test print in PLA which went perfectly, followed by no apparent issues for the smaller prints with PETG-CF, but the big print still failed - again only the top-layers.

I have almost used a whole roll of 1KG, and pretty much all of it went straight to the trash since it only failed so late in the prints. The smaller parts are still very much usable though.

Here are some images:

While printing the Sparse Infill, it looks like it isn’t printing the correct layer height, and as a result the Sparse Infill always seems to be 1-2 layers below the walls. I have never noticed this on other materials/prints, so I am unsure if this is intended or not. I did not notice this in the sliced file either.
A picture of this (pardon my poor paint-skills):

I am printing with inner/outer/infill order.
Again, I have no idea if this is intended or not, but it seems weird to me.

My current “calibrated” profile:

Filament:

I have tried from stock, all the way up to 1.05 flow ratio, 0.042 PA, 280 Nozzle Temp
Max volumetric speed I calibrated to 18 mm3/s, but decided to leave it lower for more stability.

Cooling:

I have tried no fans and 100% fans, same results more or less.

Setting Overrides:

Tried stock, and the settings from the posts above.

Process:

I am at a complete loss here, and I feel like money is draining from my hands with all these large 4-6 hour failed prints.

I am looking for any kind of feedback.

Thank you all very much in advance.

[wiremeup]

I feel for you brother. Having trouble myself with a different printer and brand filament. Something that has helped me figure out layer specific issues though is once sliced go to the box at the top right and where it shows you all the slicing stats. First scroll down on the right hand side and move down to the layer in question. Change the view and inspect the layer time, fan speed, and flow. Make note of what you see and compare it to other layers and what the slicing settings are for that type of line and that layer. Maybe post some screenshot of it.

[wiremeup]

You also might be having the same issue I believe I am having. I printed several parts successfully already and ever since a week ago with no other changes everything has failed on 2 entirely different printers in different areas of the house. The common denominators are open air printers, severe drop in ambient temperature and PETG. On the same print as before it fails several layers in and not always the same layer. I have the come to the conclusion now that the room temp is still too low and since I am halfway through the roll it’s is probably taken on moisture even though it’s in a drybox and has been dried out prior. We may be having the same issue. Once the print gets high enough that the plate does not provide enough surrounding heat the filament starts to cool prematurely before fastening to the previous layer. That or it’s wet.

[kragghc]

Hello, thank you for your reply!

I think I’ve found the culprit: clogging.
I went through with another print, this time the Aux. fan saver from BambuLab.

The print (of course) failed again, but this time caught it red-handed in NOT extruding filament at all.
I am unsure if this is the issue on all of my previous prints as well, but it would make sense, if the filament is backed up, then suddenly releases a giant blob of material, and said blob gets stuck to the nozzle, further hindering extruding, then hardening over the print where the nozzle will hit it and potentially tear up layers.

I went through the sliced preview, taking note of the speed, fan speed, flow, etc for the layer in question.
I disabled Infill Combination, to keep the layer heights consistent.
Here are screenshots of the details:

Edit:Accidentally sliced with wrong filament. Flow, Layer Time and Fan Speeds were different, everything else the same. Updated the images to reflect.

From what I can see, it looks pretty normal. Only thing I can think of, is to lower the max volumetric flow rate, to ease up on the extrusion pressure.
I did however try to lower the speed to “Silent” while printing, so it would print at 50% speed, but it changed nothing.

I continue to be at a loss…

[wiremeup]

OK here is the issue- The layer that failed is an sparse infill layer. The bambu petg-cf is EXTREMELY sticky. More than any other petg I have used. And the CF makes it very difficult to print infill patterns that overlap each other such rectilinear, hex, tri, honeycomb even though I have gotten that one to work. These overlapping patterns will only work if your ambient temp in the room is really warm circa 75F. Otherwise, once they come to the wall they cool too quickly, don’t stick to the wall and result in wisps rising upward as the nozzle retracts and the plate hops. This can also cause blobbing on the nozzle and both issues compound each other. The best infill to use is grid. The lines do not overlap, one layer just prints identically over the other. SOO, grid infill, no infill combination, turn on “avoid crossing walls”, keep infill speed lower, keep ambient temp around 75F, use modest cooling, use more walls and less infill, use higher percentage infill to reduce the distance of bridge infill as well, and use patterns that don’t have short quick back and forth movements but rather are continuous lines like concentric. Your retraction should be high and fast and flow ratio pretty low. As far as that top layer is concerned, that shouldn’t be infill but perhaps you can send a screenshot of that layer in the slicer. Also you need to dry this filament once when you get it, and then again once you reach the middle of the spool regardless of how you store it.

[wiremeup]

Rather obvious I think but you are using a 0.6mm hardened steel nozzle yes? I myself also installed the hardened gear assembly and that helped too for some reason.

[zviratko]

You are contradicting yourself - grid DOES overlap itself and I would never ever use that to print PETG-CF.

Just use gyroid for everything, unless you’re in a hurry, then rectilinear might work (but in this case the print should be slowed down anyway).

To avoid clogging you should not print too slow either,

@kragghc are you using Grid infill? Looks like it. Don’t.

[kragghc]

Hi, thanks for the reply. I am NOT using Grid, I am in fact using Gyroid. I also tried with Rectilinear, which worked pretty much the same.

[kragghc]

I am using Gyroid, as Grid has been advised against.
The ambient temp is around 25C-28C, I have “Avoid crossing walls” enabled, tried with and without “Infill combination”, tried to reduce speeds to 50%.

It is not the top layer that fails, but top solid infill - the layers just below top layer.
Except for the last print in my last reply to you, that was way before top infill layers began.

I am unsure what you mean by

@wiremeup

use more walls and less infill, use higher percentage infill

I have tried using 2-6 walls, and 25%-50% infill percentages. How can I reduce infll while having high infill? Doesn’t makes sense to me.

Also, I am using a semi-enclosed P1P, because the parts I am missing are the ones I’m trying to print with PETG-CF.

I have now just switched over to regular PETG Basic, which works flawlessly.

[kragghc]

I am using the “Highly recommended” 0.4mm Hardened Steel Nozzle, and Hardened Steel Extruder.

[kragghc]

Thank you for the recommendations, but at this point, I’m considering trying for a refund, since this seems very much like faulty… something.

When default profiles don’t work, the recommended equipment does not work, and all other filaments I’ve tried work basically flawlessly.

[wiremeup]

You need to use the 0.6mm but even then you can still get blobs. I have not tried the 0.4mm yet even though I have it.
Seriously, try the grid infill. The layer that fails especially if its top solid infill is right above you top most sparse infill layer. If the last sparse infill layer cools with lumps or wisps then the very next layer will be the fail. And NO Grid does not overlap. You can see it in the slicer. When I say overlap I mean like a lattice does (interwoven). The lattice style patterns easily fail with CF. Gyroid can be used but the toolhead moves so violently that you can easily bump something and I have had several failures attributed to that. I would say that and honeycomb are the next best thing for CF though. I’ve gone through 6 or 7 kilos of this stuff from 2 brands and have had plenty of fails to have come to this conclusion. Here is what I printed today with Phaetus ae-Worthy PETG-CF. And bags and bags of successful prints. After many fails mind you.

[wiremeup]

To clarify the infill recommendation- Use more walls which results in shorter bridges. This causes your infill amount to decrease. By amount I mean time and material spent on sparse infill. At the same time you can also increase the infill percentage. This is not a contradiction. The higher percentage results in more tightly woven infill lines and therefore shorter bridges. The top infill bridges are what kill you. They have to stretch across the top most sparse infill layer so if THAT layer is not ruler flat with no dips or hills the rest will fail and quite dramatically as you have already witnessed. and As you can see in my above photo using grid infill at a reasonable percentage that results in top infill bridges of less than 4-5mm is ideal and gets you ruler flat results. That combined with a warm room.

One other thing- are you printing the arc enclosure? Is that what that big piece is for? Reason I ask is that those files are pre-sliced files and have settings not conducive at all to petg-cf. There would be alot for you to change. They recommend printing very slowly which I did myself as I was using silk pla for the panels but too slow as the other guy mentioned is also bad for CF. Also how low have you gone on flow ratio? Petg is typically 0.94 but it should be even less for cf even though the BL preset doesn’t reflect that. i don’t know why their preset still needed calibration but it does. Also move retract length to 4-5mm. I hope all this helps.

[just4memike]

I would suggest a quick inspection of the hot end fan. Check if its running. I’d assume the machine would give an error message if it wasn’t, but still check. If the hot end fan is damaged, it could build up heat in the upper end of the hot end and cause clogs. But note, if it prints PLA fine, it’s probably not the problem.

If that looks good, slow the max volumetric speed back down to the default and go with a tried and true infill like grid to try and get a clean print. You can optimize the infill once you have a working slice.

One other thing to try, it sucks to use up all of your filament trying to troubleshoot. To get around that, slice only the section of the print that is giving you problems (sink the model into the plate using the “move” command until the problem section is on the plate or use the cut function). Test different settings on that single section until you find a winner, then slice the whole file.

[kragghc]

Hi, thanks for the reply.

There are no defects on the machine, all fans are working as intended, it prints all other filaments perfectly, including PETG. I am currently printing through the rest of the enclosure with regular Bambu PETG Basic, and every print has been flawless. As a side note: I also tried to use same settings and profile for the PETG-CF, which failed the same as before.

I have tried to lower the volumetric speed all the way down to 10mm3/s, still same result.
I did try to cut the file, then slice from a few layers down from the problematic layer to the top, but that yielded no error, and the print was flawless.

[kragghc]

I still don’t quite understand what you mean by lowering the infill but increasing infill percentage to decrease bridging. As I said before, I’ve tried with 25% infill and 50% infill, 2 walls and 6 walls. All give same results.

I am fairly certain I’d be able to print the pieces you’re printing as well, since it’s only bigger prints that fail, like I said.

I am not printing the Arc Enclosure, but this one: Bambu Lab P1P Full Printable Enclosure

I am aware that .3mf files can contain settings and profiles for the printing, but you can also just hit “Import geometry only”, which will only import the .stl file, or atleast not overwrite any of your settings.
Also, I always go over my settings again pre-printing, just to make sure it is on the correct profile.
So no, that’s not the issue.

[just4memike]

Odd, if the isolated print works fine, look for reasons for the clogging. I don’t think you have to worry about settings if you can get it to work in isolation.

Bambu’s PETG CF has a TG of 68C, which is close enough to be aware of the enclosure heating up on longer prints. How enclosed is your printer, if at all?

[kragghc]

I have the P1P semi-enclosed. It’s protected from drafts, but the temp inside is around 28C give or take, 23-25C ambient.

[wiremeup]

@kragghc

I still don’t quite understand what you mean by lowering the infill but increasing infill percentage to decrease bridging. As I said before, I’ve tried with 25% infill and 50% infill, 2 walls and 6 walls. All give same results.

You can lower the total amount of infill by simply adding more walls. More walls mean less internal space for the infill to fill. Then increase the infill percentage to get a more dense infill within those walls. The result is short distances to cross from one wall to the next across the infill. The purpose of sparse infill is to support the top infill layer. So when you are laying down filament the bridging distance between the wall and infill and then next wall is very short.
Also which piece are you having trouble with in that link you sent?

[3dsurfr]

Honestly, to me it looks like something is really off. I would:

1. inspect what the slicer produces in fine detail to ensure the top layer isn’t printed up in the air (is this a model you can link to so we can look at it?)
2. cut a smallish portion and print that while sitting there and looking at what exactly is happening
3. dry the filament for 12hrs+

WRT infill, I fail to see why you would go anywhere above 25%. For top layer cleanliness I dislike infill patterns where lines cross within one layer, for example grid, triangle, etc. The patterns I use the most are line, gyroid, and hexagon. These do not overlap lines within each layer.

The line pattern has pretty decent strength for flat bars and surfaces, but when the infill goes below 10%-12% it gets very sparse and the resulting bridging can be a problem, especially if one uses only two top layers.
Gyroid is nice for volumes because it’s somewhat uniform in all dimensions, but it’s not that strong overall.
Hexagon is strong but actually uses more filament (I would say that the %infill calculation is wrong) so to do an apples-to-apples comparison you have to reduce the % compared to line, but even with the same grams of infill it’s stronger.