I’m trying to print this object, in PETG. I’m having three distinct problems. I’m hoping to see if anyone in the community has advice.
Problems: Indicated as “1, 2, 3” in attached images.
Machine: X1C, almost new
Filament: Bambu PETG Basic, gold, gray
Nozzle temp: 255C
Bed Temp: 80C
Chamber temp: 35-37C
Speeds: 100, 50 on outer wall
Printing order: Outer, inner, infill
Flow rate cal: Yes, manual
Flow dynamics cal: Yes, manual
More info: The print shown is 1/2 of a miniaturize version for troubleshooting.
Problem 1: Inconsistent flow on outside walls, apparently, at the layers where the model’s internal geometry changes. On other printers I’ve been able to dial this most of the way out by fiddling with the flow, but I’ve already gone through that automated calibration and then manually dialed it in. I really have no idea where to look for settings solutions here. So any info that anyone can offer is much appreciated.
Problem 2: Under-extrusion at layer start. Only when the z-seam is on an inside corner.
Problem 3: Poor layer adhesion on sloped surfaces. Again, I’ve seen this before on other machines and the solution was to adjust the flow. On X1C, that hasn’t worked.
More info: The model shown is 1/2 of a miniaturize version for troubleshooting.
PETG is a bit tricky. Plenty of threads in the forum succh as this one: PETG Issues
Looks like it may be helped by using adaptive layer height (lowering the thermal input per layer at overhangs). You may also want to replace part cooling (to 10°) by Aux-cooling (to 70-80°) and go relatively slow (unless overhangs are above 75%). That should help with overhang warping.
I still have that problem as well. Orca slicer’s Pressure Advance sounds like a good way forward but I am only slowly getting into that. Currently trying the old “coasting” option in Studio which is disabled in the Bambu PETG defaults.
Are these the same problem? The lower line looks a bit blurred, while the upper line is pretty sharp. Do you have a flow ratio, cooling or speed change at those layers?
I hadn’t considered adaptive layer height. I can play with that. I also haven’t experimented with hotend temp yet, other than to reduce a bit for black filament. I had only recently read that Bambu default temps are really high to get high flow rate. At this moment I am re-running flow rate cal and I noticed that the hotend temp is 235C when the default for other printing is 255C. Maybe something there. For clarity, the slopes are not an overhang. I positioned the model on edge to get the lighting right for a photo. The model is printed with those slopes facing up. They are actually stacked top surface layers.
I’ve played extensively with Coasting in Cura. I don’t want to go there unless I have to. It’s risky because I can get the setting perfect for one model and have really mysterious problems on a different model.
If you are referring to both defects marked “1”, I think they are the same problem. They both occur at layers where there are large changes to the internal geometry, i.e. top surface layers.
Flow is is perfectly consistent over all of the walls, in Studio. Chamber fan is 70%, Par and Aux fans 0%, except for the tip of the latch where the layer time gets short.
I hope that adaptive layers will be able to resolve at least some of your issues. It did help me a lot in the past.
I sometimes struggled a bit at reduced temps (to 245°C). While helping (lots) with overhang warping, reducing the temp also led to a worsening of a strange surface defect around 1mm mm behind the seamline on upper slopes. Hence my current attempt with coasting enabled. If all goes reasonably well, it’ll be another 2 days before I know though.
I am also going at reduced speeds (60-100mm/s outer wall, 150mm/s insides).
As for defects 1) and 3), I assume you are already considering the print order to print the outer wall first?
I have also followed advise on setting the slice gap closure in Quality → Precision to 0,001mm. While it did reduce the size of the seam, I am still getting defect 2) as well.
Just had another look at an older PETG print where I used 3 rather than 2 walls.
It did not have error number 2). On current prints with 2 walls I also get error 2).
Not really sure if that was the key reason though as I was battling overhangs and support interfaces.
I just finished a test with extruder temp at 245C. No change in any of the symptoms. Currently printing with adaptive layers ON. The print is almost to the critical layer. So far it looks the same.
And yes, I am printing outer walls first, which makes the whole thing all the more mysterious.
Edit: Adaptive Layers made no difference. I didn’t play with the settings but I would expect some change. No change at all indicates that I’m not looking in the right place.
Ok, that has me stumped. Since you are already going slow and have dialed in your filaments I would have expected adaptive layers to make a big difference. It did help me a lot due to the low layer heights in tricky areas.
A final thing I found while browsing last night was increasing nozzle z-offset. Mainly for zits and blops and 1st layer issues thougg. And I have not tried myself. Since my well meant advise has proven not so helpful in your case, take that with a large dose of salt.
Scratching my head here and apologizing to you for providing advice that did not prove to be helpful to date
Increasing from 2 to 3 walls helped problem 3 quite a bit. Upon review of the whole troubleshooting process, I noticed that problem 2 only appeared when I shrank to box to reduce filament consumption during troubleshooting. That leaves the the main problem.
I sincerely appreciate all of your help and thoughtful advice. Please don’t apologize. I’m grateful.
I can see you’re using grid infill as it is showing through the top layer. As the nozzle passes over the previous lines in the same infill layer, it tends to push up the infill. Then subsequent layers are also going to be pushed up, which can cause other issues. You should change to a different infill that doesn’t cross over for PETG and other stringy filaments such as PC, TPU and especially CF infused. Gyroid or even the old standard rectilinear works better in this regard. And increase the top layers to at least 4 to prevent the infill from showing. Increasing the minimum layer time for fan speed will help with the overhang performance and is set in the filament tab under cooling. Standard is 4 seconds, try increasing this to 6 or so.
I am very glad that at least 2 of the three probs are getting there.
Actually, @RMB advise may help with that further. I had several prints fail with PETG using grid infill. Honeycomb works much better.
And with an additional top surface while ensuring upper wall thickness, upper slopes will have a bit more material and stability.
The main problem still has me stumped though. Hopefully it is linked to infill collission and can hence be avoided as RMB suggested. Other z issues I have seen in the distant past were repetitive and a hughe pain to resolve.
On the Bambu, I have only read about belt tensioning (which woul give a 2mm pattern in z), flow and slicing software bugs. The pic does not look like any of these.
Very interesting to spot scaling effects. If it was freestanding walls, I could understand downscaling to lead to artifacts. But it does look like its classical walls so still a puzzler.
I have already switched to gyroid infill. No change. I haven’t worried about the infill pattern being visible on top surface layers. And I do have z-artifacts that change with wall speed and that could have more challenging solutions. But again, I’m not as concerned about those for now. This machine already produces print quality that far exceeds what I could get from any printers that I’ve previously owned. I’m trying to keep myself from getting greedy for now. I’ll fine tune later.
The thing that gets me is that the person that created the original model is able to print the box without any of these issues. Others are able to do so. I must be doing something different. It sounds like the creator is printing in PLA, but I’ve seen variations of Problem 1 with PLA on other machines. I figure that I can’t be the first to encounter this.
On close inspection of my latest prints, it appears that there are two modes to Problem 1. One is that the layers with infill appear to pull the sides in and then there is a reset if you will, at the layers that have top surface lines. At this point, the straight wall outline is restored, resulting in a step in the outside wall. The evidence of this is that this defect is not as visible near the corners. The walls bow inward. The second mode looks like the walls are larger above the layers of the highest internal features. They step outward, on all sides, maybe 0.1-0.2mm. This is true of the inner and outer walls. They all step toward the outside of the box. Does that help to clarify or confuse?
Edit: Thinking about this just after clicking “Reply” I recalled that the first of the Problem 1 modes also appeared when I shrank the model. I only see the outward expansion in the full-sized prints.
Actually, it does make sense to me. The X1C is an amazing machine, in particular with PLA. I would not be surprised if an attempt with PLA would turn out perfect immediately. At least, it would confirm that the problem is not machine related.
PETG is quite a bit more challenging due to its high tack (making the nozzle a material “magnet”) and susceptibility to warping.
The latter would match your description of problem 1 both for the infill pulling in the wall and the infill closure layer (turning a soft infill into a brutally stiff sandwich structure).
However, in this case I would have expected that you should have been able to see a difference when increasing the number of walls.
Printing infill before the wall so that it has already shrunk when the wall comes into play could perhaps confirm this. It might decrease the infill-wall anchor, but at least the wall should be straight if the assumption is correct.
That is an interesting perspective. I’ll admit that I’m new to both PETG and the X1C.
I find the combination well, as of today, frustrating. I just printed a full-size, half box and found Problems 1, 2, and 3. That is with 3 walls that improved the smaller version.
I read your last message this morning and reversed the print order for the most recent print, with infill first. I’m sorry to report that there is no change.
I am well and truly stumped. I think I just need to print this box as-is. Sometimes it’s better to come back to a challenge when I have more experience.
Yes, Bambu PETG is rather tricky. Printing Cults stuff for the garden (or trying to), I am particularly struggling with overhangs. Its really good. Until I get to 25°. Then it becomes a warped and stringy mess.
I think it is a wise choice to make a problem simpler by, for example, going back to PLA for a particular print. For most of us, it is a hobby. And hobbies are supposed to be fun.
At some point, PETG may become interesting again. It may then be worth remembering that the Bambu PETG seems to be tailored for high flow. PETG with other, non-high speed formulations from other sources may behave better.
At least that is something I’ll try for an upcoming translucent print. A few low-poli unicorn heads I did on the X1C in the past were OK with standard generic settings. Simple geometries though.
Well, 3 months on I have quite a bit more experience with the machine. I have not gone back to the model that I asked about. But I have learned a lot from printing many other objects. If I were to go back now, the place that I would look first for a solution to problem 2 is stringing. There wasn’t a lot of obvious stringing at the time but I’ve found that it doesn’t take much to cause a problem. On more recent prints I’ve found that I need to slice so as to minimize the use of short gap infill lines. For some reason I don’t understand, retractions on these don’t seem to work well. I get little kisses at the end of these lines.
I’ll fine tune later.