In one print, AMS pushes so much filament that the tube comes out

[smst]

Hi all. I’m having a problem with a specific print on my A1 with AMS Lite.

I’ve had the combo for a few weeks and have had several successful prints with models from Makerworld (both single- and multi-filament with AMS handling the changes), and have printed some single-filament models that I’ve designed.

I am having a problem with a coaster-like model I’ve designed, using all four filaments. I designed it in Tinkercad and exported it as .obj & .mtl, then opened it in Bambu Studio and sliced it successfully. (In fact I started not with the full model, but with just a chunk - I used Tinkercad to extract a smaller cross-section so I could test how the top and bottom layers printed in particular.)

I can start the print okay, and even print a few layers, but after a while I get a message about filament being stuck. Each time I’ve come back to the A1, I’ve found the AMS has been feeding in too much filament, and the 4-in-1 PTFE Adapter has been pushed out of the Filament Hub (with tens of cm of the current filament sticking out of the end).

The first time this happened I wound the filament back in, replaced the adapter and resumed. A few minutes later it happened again (but not instantly as far as I can tell - I think it printed more layers first).

I cancelled the print and tried slicing and printing again, and got the same problem after about 5 layers. This time it was a different filament (in a different slot) that failed.

I’ve confirmed that all four filaments work in their current slots by printing a small test model from Makerworld which uses all four on the same layer, for multiple layers - I did this after the failures.

My best guess at the moment is that it’s not enough to have designed the model, I also need to configure the print or slicer settings in some way to avoid this - make it hotter, make it slower, something else? I haven’t changed anything from the defaults, except mapping the filaments (which were detected correctly by the AMS Lite).

I do remember that when I hit “Slice plate” I got an error that a “G-code path goes beyond plate boundaries”, which was because of the prime tower (which the slicer had added itself!). I moved it back on to the plate and started the print.

Does anybody know what could cause this, or what settings I should look into?

[MalcTheOracle]

Do you have photos?

[smst]

Bottom view of partial print:

Top view of partial print:

I don’t understand why the black and yellow/gold has been printed like that on the layers above the first - another setting I suppose? The rectangles are visible from the underside which is not wanted. Same with the red triangles. Could these artefacts be related to the problem?

I have exported a .3mf file, having imported the .obj to Bambu Studio.

coaster 3 (3mm).3mf (97.0 KB)

[MalcTheOracle]

Photos of the filament leaving via a route you said it shouldn’t.

[smst]

I do! I was just adding them to a comment when you asked. Please let me know if there’s anything else I can add. Unfortunately I don’t have a picture of the printer when the tubes came out, but I can try to describe it better if needed!!

[MalcTheOracle]

A photo of where it came out would be great.

I have a condition called aphantasia which means I can’t form visual images in my mind. Photos help me work things out.

[smst]

I can at least mark the spot on the (intact) printer. Where my yellow arrow is, that top square of white plastic had come out of the cuboid it’s inserted in. It seems that so much filament had been pushed through the tube, with nowhere for it to go, that this part just popped off. And then another 50cm or so of filament continued to be pushed by the AMS.

Of course I then checked for a blockage and didn’t find one, but I think it’s relevant that I was able to print something else successfully afterwards, using all four filaments, so I think that means there’s no permanent blockage, at least.

[smst]

Ah yes, understood. If the image I’ve added isn’t helpful enough for that reason, I can start the print again. Either it works (hooray! But I’ll still want to understand it), or it doesn’t and I can take a picture.

[MalcTheOracle]

Did you notice and physical damage or deformities to the filament end that was push out?

I am wondering if there was a thick section, a braid, barb or other issue that could mean the filament was too wide to make its way through?

[smst]

I didn’t notice anything like that, no. I won’t discount any ideas of course, but counting against that possibility is the fact that it happened three times with at two different filaments, both of which went on to print a different model successfully.

This is why I’m wondering about print settings, as the physical setup has worked before and since.

[MalcTheOracle]

OK, I am risking my printer.

Differences:

1. A1 mini
2. AMS (not lite) using new buffer
3. I fixed your painting (not sure if you did it), so there is only one black. ^^
4. I moved the prime tower onto the build plate. ^^^
5. I am using only Bambu Lab filaments. ^^^^

^^ Try to limit your filaments before you paint (in the filament pool, prepare tab), it limits or prohibits mixing up two identical or very visually close filaments.

It adds to the complexity as it marks out two zones of travel for identical filaments.

^^^ This is why you received the warning about travel. If you printed without fixing this, it may be the whole issue.

You can position the prime tower anywhere in the plate. I suspect this was partially caused by the 2nd black pushing off the back of the build plate. Dangerous.

^^^^ While I have other brands, I can’t see this being as cause, I can perform another test using all generic filaments if required based on this result.

Update

Still printing and nothing broken.

[MalcTheOracle]

It printed without problems and zero damage.

I believe the issue is related to the GCODE warnings you receive, but you said you moved it and before slicing again.

[smst]

Thanks so much for diving into this @MalcTheOracle , that’s illuminating. And thanks for risking your printer; that was above and beyond.

As you advised, I’ve fiddled with the filaments this morning - I suppose my original model had two slightly different versions of the same colour (looked like the white when I checked it just now). When I sliced this time, the prime tower was on the plate, which is a good sign! I did move it onto the plate manually last time, but the fact that was necessary was a concern already I suppose - if the slicer can’t get it in the right spot, something must be wrong.

I set the sample printing again last night, hoping to get a breakage picture - no breakage. So I risked running the full print overnight (without the filament fixes you’ve just mentioned) and it came out fine! Which is good, but annoying from a diagnosis and understanding perspective.

Examining the finished product, there’s some roughness on top, and that jogs my memory - it’s possible I had turned on ironing of the top layer when I tried before. It wasn’t the top layer that failed though, so I don’t know how relevant that is. Now a little nervous to try ironing in future!

I have one more question, about the successful print (photos below; dog picture is based on an SVG from Tibbixel). The model is solid red around the border and solid white through the bulk of the body. Why then is there red cross-hatching? Can I hint to the slicer to use the white for that (presumed) infill instead? It’s most visible on the breakfast side, which is the bottom of the print.

Thanks again for your attention and help! I am enjoying learning about this hobby.

[MalcTheOracle]

@smst

Examining the finished product, there’s some roughness on top, and that jogs my memory

You can improve this a bit without ironing.

• Select the cog (hex) icon to the right of the build plate
• Choose the two filament sequence options and edit them (at the time of righting, last two)
• Change the order to reflect light (leftmost) getting progressively darker as you move across (rightmost)

This will then lay down white before darker colours, moving to the next colour and so on. Thus has the effect of limiting contamination from darker colours into lighter ones.

I experienced when doing the text print. It sometimes increases the print time.

@smst

Why then is there red cross-hatching?

Often as it continues using the last filament used to do the infill. Also, it aims to limit ‘unnecessary’ filament swaps, more on that shortly.

@smst

Can I hint to the slicer to use the white for that (presumed) infill instead?

Yes, but not using the phrasing you used.

Currently, you can’t specify a different infill material.

You can add a Modifier shape. You then add your colour to this, it will override the main model and use that choice, plus any other setting tweaks for the areas it overlaps.

• Select your model
• Right-click
• Choose ‘Add Modifier’
• Choose ‘Cube’ (best for this use case)
• Select the new Cube
• Select the Scale toolbar icon
• Turn off the Uniform Scale
• Enter an X & Y size the those of the coaster, less a few millimetres for the red border pattern
• Enter a Z slightly thinner than your coaster to account for the top and bottom layers
• Right-click the Cube
• Select Centre
• As this only centres to the build play X & Y, you need to adjust the Z position
• Select the Move toolbar icon
• Make sure the Z value is zero, this should position the cube in the middle of your model, if it doesn’t p, adjust to suit
• In the Prepare Tab, locate the Objects list and make sure the Cube is selected, it probably is.
• Select the swatch on the right to change the colour override from (not overridden) to a filament colour you choose.

Alternative, design a perfectly fitting shape to occupy the white portion and use that as the imported STL modifier instead of the cube. All other location instructions remain.

Consideration.

Doing this will force filament swaps on every single layer. This will greatly increase the print time and production of waste.

Alternatives

1. Set the top and bottom surface layers to at least 5 each. This will make a thicker surface through which any other internal colours will be less or not visible.

2. Consider having the surrounding red border only appear on the first and last few layers (think 5 each).

   You could then use a simple layer height modifier to set the colour of the central portion raptor be white meaning that entire section prints without pausing.

   Ask me how if you would like to know.

[smst]

You can improve this a bit without ironing.

Thanks, I’ve set that up and will try my sample again with that configuration.

You can add a Modifier shape. You then add your colour to this, it will override the main model and use that choice, plus any other setting tweaks for the areas it overlaps.

I started this and ran into difficulties, but only because (for boring logistical home IT reasons) I’m running Bambu Studio on a very old laptop and accessing it over RDP. It is not responsive or beefy enough to make those changes. I’ll try again on a different computer later, or by making the modifier shape in Tinkercad and importing.

For my understanding though: why is this modifier necessary when the original model in Tinkercad had a solid white body? I can see that the slicer has replaced the white with the cross-hatched red, presumably to save filament changes as you indicated. Does the modifier object hold more sway over the slicer’s decisions than the original model?

I’d be happy with changing the top / bottom thickness to 5 as you suggested, and leaving the slicer to do what it wants in the middle. (I do want to keep the external walls as red all the way through.) Where would I do that? I can see “Top interface layers” and “Bottom interface layers” in Support, but it won’t let me go above 3. And maybe that’s not what you’re talking about! I guess the setting you mention is intended to tell the slicer how many layers to consider the “top”, and therefore under my control, and beyond those layers it’s free to do what it wants because it’s all internal?

Thanks for your ongoing help! Obviously I have my print now, but I’m still really interested to understand these settings, and be prepared for future coaster-like projects. (Or any projects really!)

[MalcTheOracle]

@smst

Does the modifier object hold more sway over the slicer’s decisions than the original model?

Yes.

@smst

And maybe that’s not what you’re talking about!

Not there.

@smst

I guess the setting you mention is intended to tell the slicer how many layers to consider the “top”, and therefore under my control, and beyond those layers it’s free to do what it wants because it’s all internal?

Exactly.

In short; the top and bottom shell layers are the number of entirely solid surfaces. They are the bottom (near build plate) and top (the last surfaces printed).

It is worth noting that top and bottom are not the first and last layers, but they could be. What does that mean? Imagine you are printing an open stair case. Ignore every thing else. Just think the stairs. The top and bottom are the layers related to the model and not the cube you could place it in. Each step would have a bottom and a top, all 13 or more of them, even though the bottom step is much lower than the top step. It is about the bits of the model and where they are located.

For a coaster it is simple to understand, but, that might make you think it is topmost and bottom most of the model, rather than the intricacy of the model contours.

Making to your current issue.

Pictures help.

• Top layers in red, set to 5.
• Make sure the top and bottom shell thicknesses are set to zero. If not, it will ignore your choice and use this value.
• Bottom layers in blue, set to 5.

A value of 5 with a layer height of 0.2 will be 1mm thick. 1mm should be considered the thinnest for white material in order to height any colours below it.

You also have Walls, not important for this project, but knowing it helps my next point. Walls is the number of solid lines around the edges of a model. Again, irregular shapes have walls that wrap those irregular shapes and they do so from the bottom to the top.

Infill, is everything that isn’t walls or shells.

[smst]

Right, got it. Interestingly both of my top/bottom values were already 5, and the thickness was 1mm (which matches 5 x 0.2mm layer thickness). However the “Bottom paint penetration layers” value was 3 (vs 5 for the Top) and the red infill is more visible in the bottom. I’m trying again then will reprint the full coaster (which has a thickness of 3mm, whereas my sample has only 2mm, so in fact I can afford to increase the paint penetration a little more on that one).

Thanks again, I’m learning all the time!

[MalcTheOracle]

@smst

Bottom paint penetration layers

Unrelated to your activities here.

[smst]

Sorry, my imperfect understanding again! When I change “Bottom paint penetration layers” between 3 and 5, slice the model and inspect layer 4, I see different results.

• With 5, the colours from the bottom layer are visible on layer 4 (and 5, but not 6).

  

• With 3, the colours from the bottom layer are replaced by solid red on layer 4.

  

[smst]

Well, despite a successful print of the full model a few days ago, and successful prints of the sample section with new settings (filament order, and change to paint penetration), I’ve had another failure.

The assembly came apart at a different point, but the principle is the same: the AMS was pushing filament which had nowhere to go so the assembly popped apart, and then it continued to push filament for a while.

Since this has been intermittent, I think it’s time to contact Bambu support. Thanks for your help, @MalcTheOracle .