PLA layers squished following PETG support interface layers

[RyanEwen]

Bambu Studio Version

1.6.2, 1.7.0 public beta

Where is the application from?

Bambu Lab Official website, Bambu Lab github releases

OS version

Windows 11

Additional system information

No response

Printer

Bambu Lab P1P

How to reproduce

Use settings like so:

Print a model with a flat overhang needing supports (I use normal / manual with the overhang painted using the fill tool)

Actual results

Note the bulged layers all the way around the entire model, aligned with the PETG interfacing

I have tried using 0.2 mm Top Z distance as well, in case that was the issue. It did not help.

Expected results

Expected the PLA portion of the model to appear how it does in the slicer preview, or when using PLA supports.

Project file & Debug log uploads

I cannot share this particular project unfortunately.

Checklist of files to include

• Log file
• Project file

[SaltWei]

Not slicer issue. Can't see the line on preview page.
Could you share gcode.3mf (no model 3mf) for us to reprinting?

[SaltWei]

1.6.2, 1.7.0 public beta

@bambu123 Not issue related 1.7.0 version

[RyanEwen]

Not slicer issue. Can't see the line on preview page. Could you share gcode.3mf (no model 3mf) for us to reprinting?

Yes it does look okay in the sliced preview.

FWIW I have tried with various filaments including Bambu PLA. I have printed many different variations of the model as well, but it always happens. I used to have a second supported structure at a different height and the same bulge happened there as well.

Attached gcode is uses Bambu Basic PLA in AMS slot 1, Bambu Basic PETG in AMS slot 2.
The file with CUT in the name is a shorter / cut up version of the same model, to save you time and filament.

Edit: don't use this file, use the one in my newer reply
gcode.zip

[SaltWei]

OK. We will reprint this gcode file and try to find and analyse the cause. Thank you very much!
@QingZhangBambu Please follow this issue.

[Hologos]

What is your flushing volume between the PLA and PETG? You have to flush at least 700 for the nozzle to be clean. PLA and PETG does not stick to one another so if the nozzle is not clean, PLA and PETG will mix and cause a layer separation.

[RyanEwen]

What is your flushing volume between the PLA and PETG? You have to flush at least 700 for the nozzle to be clean. PLA and PETG does not stick to one another so if the nozzle is not clean, PLA and PETG will mix and cause a layer separation.

I use 800, but the gcode attached above might be only 250 as I rearranged the filaments (moved PETG to slot 2 and deleted 3).

I will reslice and attach new gcode example.

Some other slicer settings I should mention that I'm using:

[RyanEwen]

Earlier gcode likely had 250 flush instead of 800.
Support painting may have gotten lost in the CUT file as well.

This v2 file has 800 flush and the support is painted onto the CUT file:
gcode.v2.zip

[RyanEwen]

It occurred to me that I'm using 4 interface layers while the dropdown only offers the choice between 1, 2, or 3 (I manually typed in 4). I thought maybe that could be causing the issue so today I printed with just 2 interface layers instead of 4 (I didn't choose 3 because going down to 2 saves a couple of filament changes). Unfortunately the issue remains.

I've also updated the photo in the OP with a better one.

[QingZhangBambu]

We will check this.

[Hologos]

@RyanEwen This happens to me as well when there is a transition from sparse infill to solid layers. Isn't this the case?

[RyanEwen]

@Hologos that's a different issue but coincidentally that also happens in this model. You can see what you described just above my thumb in the photo in my original post.

The bulge I'm trying to resolve is in line with the white PETG support interface layers and there's no change in infill in the model there.

In a previous version of this model there was post that stuck out of the diamond shaped hole, and that post required supports. The same bulge occurred there as well.

[Hologos]

@RyanEwen I downloaded the gcode you posted and it's kinda weird. There is no transition near the outside wall with the first ring flaw, there is a transition near the inner wall. I don't see anything that should cause the second one. Is the ring all the way around? It kinda looks like a layer shift (the upper part is moved forward).