Print fails around 3/4 every time

Hi community,

So, I’m trying to print this design: Desiccant boxes for AMS 2 Pro - Free 3D Print Model - MakerWorld

I’ve now made about 4 or 5 attempts to get it printed. But they failed every time and I’m out of options/idea’s.

First prints started to move or tumble over about half way. So I tried adding 3d print glue to the bed, no success. Then I thought they got blown over by the cooling from the sides, decreased it a bit, no success. Then last night tried printing a single object with Bambu PETG, added glue, added a brim. All looked good, it almost finished with only half an hour to go. But then, just when I looked I noticed the top of the single print (first photo) was all messed up and getting stuck on the print head. Eventually the whole print got detached and the print head started to move it around.

I’m not completely new to 3d printing and all other prints I make are just fine. But this one really puzzles me.

It’s being printed on a X2D with AMS.
Using stock Bambu PEI plate and 0.4 nozzle.
I’m using the first profile: Full set without hygrometer

I thought it might be the filament so bought the genuine Bambu PETG.

The other photo’s show the previous failed prints. Most seem to fail around 3/4.

Please share any thoughts and ideas to get me to a successful print.

Warm regards,
Onno.

Have you tried slowing down the print? There are a lot of small thin areas in that file.

Classic curling failures from what I can see.

Pre-requisites:

  • Modern printers are much more susceptible to moisture in the filament. And new filament is usually quite moist as the bags slow, but do not stop, water uptake during its sea journey. And PETG is particularly sensitive. Always make sure you have dried especially new rolls yourself.
  • Good bed adhesion: Give the plate (another) really good scrub with water, dishwashing liquid and a stiff, clean brush. Brownie points for each repetition :wink:
  • Consider a brim or mouse ears to improve edge adhesion
  • In extreme cases, you can also increase first layer temps slightly. But this should be a last resort after lots of vigorous scrubbing.

Curling prevention:

  • Same as warping prevention: Print in a warmish environment, avoid drafts

That is usually enough. But some prints can be more difficult.

  • PETG is particularly prone to material pick-up on the nozzle: Wipe on retract can help
  • The more heat goes in per time/volume, the higher the temp gradient during cool down, the more likely warping and curling will be a problem => Slow down and/or reduce layer height.
  • The higher the print, the bigger the moment arm during collisions: slow down with increasing height.

Special case:

  • Lots of tiny pillars per layer: Give each layer sufficient time to cool, so that “slow down for sufficient layer cooling” is not triggered => Print two models at the same time (can also be a prime tower). You want to make sure that the nozzle is away from the model for it to cool sufficiently to add the next layer.

:four_leaf_clover: & :crossed_fingers:

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I hate AI dribble. 90%+ of those bullet points clearly have zero relevance.

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What nonsense are you talking about?

EnoTheThracian is known for always giving good advice. If you think that sounds like AI, it’s probably because AI copied it, not EnoTheThracian. That’s common knowledge and relevant to topics like this. If it seems generic, it’s simply because it’s been posted here so many times already.

Or is this a new trend where people label everything they disagree with as ‘AI’ without contributing anything to the discussion?

In case you weren’t paying attention in physics class: Even if something is vacuum-sealed, moisture can still get in - even through the plastic packaging. A vacuum provides good protection, but it isn’t perfect. Common weaknesses: micro-holes or tiny cracks, material permeability, and welds/seals. Unfortunately, there are cases where vacuum-sealed filament arrives at the customer’s location humid for various reasons.

Even freshly unpacked Bambu PETG must be dried, just as Bambu itself states:

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I would not ordinarily use supports for an object of that size, but the walls appear to be very thin. PETG is kind of sticky, and may be pulling the model out of shape as the nozzle turns corners.

Painting supports on vertical surfaces can help stabilize the print. I would place them on the corners, using a pen large enough that the support wraps around both sides. Set Support/object XY distance to a small value, maybe 0.15mm. The support should not touch or scar the model, but will restrict its movement.

Though PETG must be kept dry, I do not think wet filament is the main issue here. If it were, you would see problems in the lower layers, not just near the top.

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Well, I am seeing this wrong. My apologies to the people here. Rereading the original post shows a bed adhesion problem.

Incidentally, I printed these same things on my X2D with PETG (if me using the supplied plate and Bambu glue stick. Mine came out fine.

Again, sorry for the misunderstanding.

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Now being on my laptop rather than my phone, I can have a closer look and provide better observations, experiences and explanations.

But first,

Many thanks for the compliment. :heart:
I try. FDM keeps me humble though as it has so many interconnected parameters and influences that, just when I think I understand it a little bit, something unexpected forces me to learn more. :heart:
AI seems to be a slow learner though. While I think this community finally managed to teach AI about the importance of drying filament, I am still waiting for AI to understand that fiddling with z-offset gcode to address a contaminated build plate is not such a good idea :sweat_smile: Especially when modern slicers allow easy checks using 1st layer line width :joy:

Accepted and appreciated. :heart:

So looking at the pic’s on the big screen, my prior advise still holds. But the priorities change a little.
It was mainly the blue circled failures as well as my still vivid memory of my road to succesful dessiccant containers back when Bambu released the original PETG Basic (with, at the time, really bad default profiles) that led to me to point to curling first.


For a print like this, curling (a hot layer cools down rapidly on top of a cooler but still soft edge and overhang area) is a real threat as hot layer cool down can be very rapid while lower layers are not cool/strong enough yet.

Nevertheless, I now assume the first pic to really show a smoking gun (addressed by my last point above):


From the brim being attached, I assume that at least this print did have good bed adhesion (blue arrow).
Green arrows: Wide print, lots of pillars, overhangs significant but doable
Orange arrows: Narrow print, few pillars, overhangs significant but no worse than before
Besides curling, what I have experienced with these type of prints is that the “Slow down for better layer cooling” kicks in. If enabled, the print is slowed to achieve the layer time set in the “Max fan speed threshold”.

In cases such as this, it can however trigger the law of unintended consequences: By slowing down the print, it will not only give more time for the layer to cool. It also keeps the nozzle in contact with the print for longer. This can inject much more heat into the tiny pillars. And with the part fan moving with the nozzle to the next pillar, the heat just stays and accumulates. So the effect of this parameter can actually be rather counterproductive. The Min print speed parameter is intended to counteract this somewhat, but that just forces the printer to limit its slow-down, bringing us back to the original problem “Slow down for…” was intended to solve…
==> You’ll probably want to increase layer time by printing two or more dessiccant containers at the same time.

The remainder of my advice above still holds. Although you may want to fiddle with “Wipe on retract” only if covering the pre-requisites, curling prevention and printing multiple containers at the same time does not give the desired result.

There is one more item of (minor) note. Although the consensus seems to be that filament color should not really have much of an influence, my past work involving nanocomposites have made me appreciate the massive effects that nanoparticles (like pigments) can indeed have on all kinds of properties. In particular, but not only, viscosity and hence rheology. I personally do have the impression that particular colors do print slightly differently: blue in particular but to a lesser extent black as well.
But I may be imagining this. Hallucination is not limited to AI :joy: :joy: :joy:.

:crossed_fingers: & :four_leaf_clover:

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@EnoTheThracian Thank you for your elaborate explanation and tips.

I’ll start with extra drying the spool and printing two small containers with a brim.

Hopefully, this gets those things done finally.

I’ll keep all of you posted.

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What a wonderful (NOT) AI generated slop of an answer!

Ok, so I went on and dried the PETG for about 5 hours.
Thoroughly cleaned the build plate, added some glue and a brim. Also added a second container to the print as proposed.

Again, at nearly 3/4 in, it failed again. :frowning:

For some reason, the container in the back got worse and stuck to the printhead, eventually knocking over the good one in the front.

As you can imagine, I’m getting a bit frustrated by this. Especially because:

  • others seem to have no problems at all with this print
  • I just can’t figure out what’s causing this

Again, it seems to breakdown at the end. Which it pretty annoying as it takes a lot of time and filament to test out different settings/possible solutions every time. Again, because I don’t know what’s causing this.

In the photo’s below you see the result, the ‘blobbing’ on the one in the back, and the nice, problem free one in the front.

Any more idea’s are welcome. Still convinced I’ll succeed one time with this print and knowing the root cause so I know how to deal with this stuff in future prints…

Photo1: the error free one that was in the front
Photo2: the blobbed container which was in the back
Photo3: failed result

Thanks for reporting back.

5h drying time is bit short.

Temps & Times at the end. All around 12h.

I do imagine I can see some tip curling at the back of the first photo?

To counteract overheating further, you can seperate the two containers by placing 1 to the front of the plate and one at the far back.

Again, I may be imagining things, but did you observe an increase in wobbling as height increased? In that case, you may want to slow down (silent mode) and enable wipe on retract.

:four_leaf_clover: & :crossed_fingers:

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This specific model is basically a retraction torture test. Do not use aux nozzle. Dry your filament extremely well. You should be able to tease out other relevant settings while using the built-in retraction test [9 spire thingy]

I would also put the machine in silent mode / low acceleration/jerk. I know bambu’s software dept gets aroused by shaving 4 seconds off a 3 hour print by setting accel to 10k, but tall wobbly things are still very vulnerable to the entire machine swinging around, and default accel/jerk shakes the whole machine around, including the thing stuck on the plate.

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I printed these exact same components in ASA, so the model itself is printable. With PETG, this looks more like heat buildup/cooling on the upper layers. The small top features may not be solidifying before the nozzle comes back around and once one edge curls or blobs, the nozzle catches it, drags more PETG onto the part, and it snowballs into even more melting/blobbing. Eventually the print gets knocked loose and collides with the other parts.

One thing to try is moving same-height objects much farther apart on the build plate, ideally front/back. That gives each layer more time to cool because the printhead has to spend more time away from each part before returning.

Also, increasing minimum layer time or adding temporary supports around the tall corners could help too.

Hi all,

I’m now trying to print two holders, incorporating the most mentioned tips:
1: placing the objects further apart
2: set it to silent mode

I’m not using all the tips right away, since I’ve learned that to get to the root cause, you shouldn’t change to much at once because then you’ll never know what the cause was.

I really want to use this ‘issue’ to gather as much experience as possible for the future. So that when a different print fails, I know which options I have and which do what to the print.

So please bare with me :wink:
Below the current placement of the two object.

In the end, I’m still wondering why apparently everyone else is printing this seemingly without issues except for me haha.

Anyways, in about 5h we know if these two changes were a success or not.

Note: first try btw was with all the objects at once. But because that failed together with another full print try, I was printing just one to troubleshoot. Not wanted to waste 8h and a ton of filament each time just to have it fail again.

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Victory! Well .. kind of :wink:

Of the two, one survived!
I happened to look at around 77% and both still looked good. Then around 85%, I looked again and noticed the one in the front wiggling and picking up blobs of filament. At the same time, the one in the back stood sturdy and didn’t move at all when the print head was on top of it.

So first I skipped the object in the front and had it continue only on the one in the back.
Because all your pointers point towards a heat issue, I checked the aux fan settings. And to my surprise, they were switched off! Which IMHO, would only make things worse right? Shouldn’t they be running at least?

I also noticed that the placement of the front object is ‘outside’ the aux fan exhaust.

So when I skipped the front object, I also set both aux fans to 40% and had it finished the survivor. This one really looks good.

The changes I made for this run were placing them apart and put the printer in silent mode ( Where is silent mode? , in case anyone ends up in this topic not knowing how to enable that, like me).

The fact that I finally was able to print one object completely with these settings, I think the root cause of the issues is indeed heat / heat buildup. Do you agree?

That could also explain why the front one failed, as it sits way outside the aux fan duct’s reach (I guess).

Though, if we agree on the above, the things I don’t understand are:

  • Why did the aux fans went off/to 0% at the end? (I’m pretty sure they were on in the beginning). How to check/change?
  • Why does it seem like I’m the only one (well, at least two, because I found another comment at the print from someone with the same issues) with this problem? Could it just be the sheer amount of variables? Like even ambient temperature. It’s around 20C at this moment.

BTW: I didn’t mention it in the initial post, but I’m printing with the main nozzle.

So far I want to say thank you to anyone who commented with hints. We made it this far together :wink:

Still 4 prints (objects) to go.

But below a photo of the survivor of this run, on the left obviously.

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Have to say, even the “survivor” doesn’t look that great. Would love to see you try another type of filament or others try and print this, as a comparison.

I just became aware of these Speed adjustments in Studio thanks to CNC Kitchen:

It looks useful for reducing speed and acceleration near the top without slowing the entire print and may allow even slower speeds than Silent mode.

It is hard to see from your photos but I don’t see any signs of supports. It could be that either you have not switched supports on in your set up or your overhang value is too small. I have recently bought an H2D and after many hours of printing with PAL, PETG and ABS on the same bed plate as the one in your photo and never had a print detach. You say you are not totally new to 3D printing so I hesitate to say one of the most important things before starting any print is to make sure the plate is spotlessly clean and calibrated. Hope this helps.

Hi!

Thank you for your input. Never be hesitant to mention the most obvious, as it sometimes is the most easiest to overlook :wink: But I indeed made sure the build plate was spotless and clean from fatty residue. As mentioned before, the objects that got detached were mainly being knocked over/draged around by objects being stuck to the print head.

In regards to the supports: the print mentioned it was printable w/o supports and I also saw no comments mentioning support, hence I didn’t draw them.