Random Superfluous Seams Appearing On Top Layers


I have an X1-C and I’m unable to move forward with my current project because there are random seams appearing in very conspicuous locations on nearly every print. I don’t mean random like the “random” setting. They are neatly lined up, but they aren’t the seams that show in the slicer preview, which are tucked neatly into the corner. In fact, they do not show up at all in the preview.

If I do three identical models on the same plate, usually one of them will be good and the other two will have a seam appear, both in different locations. If I delete those two and clone the good one (even though they are all clones to begin with) the seams will show up again, but in different locations.

The only thing I can think of that may be useful to mention at this point is that all of my lower layers and infill are monotonic lines/grid, but the top layers are concentric. I don’t know why this would create any problems, but I’m putting it out there anyway.

This is my own design, created in Bambu Studio. It’s just a primitive cube that’s been stretched, flattened and has beveled edges.
4 wall loops, 3 top surface layers, mostly .2ish height, .42 width, silk PLA (but it happens with any filament). Again, the problem is on the top layers only. The bottom surface is perfectly clean.

Thanks for reading and for any insights you may have.
(This is my first post here… I hope I haven’t made any glaring mistakes.)

May I assume that you are referring to this horizontal line?

A picture doesn’t really helps us help you. There isn’t a lot to go buy here. This could be caused by many factors and without access to the actual model, it is very hard to diagnose. If you care to upload a copy of the offending 3MF, it will help us help you. Outside of that is pure guesswork.

So while we’re “guessing”. If you could show a screengrab of what the model looks like in the sliced window, that will say a lot about the design intent.

Some possible random thing that can be tried:

  1. Simplify the model using the right-click simplify command and reduce the number of vertices. If the seam changes then that’s an indication that there model geometry may be facing a Moiré pattern born out of coincidental mathematical aberrations from the slicing algorithm.
  2. Try changing the layer height. Again, to see if it has an affect.
  3. Change the seam position under the quality menu.
  4. Try out scarf joints although I highly doubt it will do anything it will rule out a geometry issue.
  5. Experiment with change the wall layers, top surface and bottom surface.

Again, this is all random thrashing without a good working theory and without seeing how the model sliced or how the model was intended to look, it’s hard to help you. Also, silk is the worst filament to photograph to see what is happening. Have you tried to use a monochromatic color? That will show where the flaws are much more readily with less guesswork.

Panels.3mf (540.0 KB)


This was before I increased the number of top layers. Obviously there’s some other stuff going on too.
Thanks for your help.

I’ve tried the simplify function, (as well as “fix”) but increased rather than decreased. I’ll try that next. Otherwise, have played with layer height, wall loops and various surface layer amounts…

OK. This is helpful. I am going to do a first print test with whatever I have in my P1 and see if I can reproduce the same results using your settings.

Unfortunately I could not reproduce your artifact. I used Plate #3. Please confirm that Plate #3 was able to create the flaw.

What I might suggest is to take any of the offending models and print it on its own plate at a 30 Degree angle. If the line changes then there may be a mechanical calibration on the belts that may require investigation.

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These were all printed on PLA Cool Plate.
Coincidentally, just before checking back in here I started a print at a 45 degree angle. When finished, I’ll try 30 & let you know.
I appreciate your time in testing and responding. This is helpful.

Oh, BTW, I have plate recognition disabled.


Did two double prints, one at 45°, one at 30°. Same results. I’ll try a few solo.

Well hold on for a moment. Why are you getting two different results? What is different between these two models?


I don’t think my test has been proven as valid. The 3MF you uploaded had multiple models on multiple plates.

As I stated, I printed one model from plate 3.


Can you confirm which model was at fault or better yet. Upload and isolated model 3MF with a single plate. If we are to help you, its important to have a test file that reproduces exactly what you saw. Remember rule #1 of troubleshooting: Change only one variable at a time.

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That’s what makes the problem so “random”. The results are never the same. If you look at the pic in my first post all three models have a line, but it’s in a different location on one of them. On plates containing multiple models, 2 of them may have the line appearing in a different spot on each and then no line at all on the third.

Sorry – I thought the 3MF file I sent was just one plate… didn’t realize there were multiples.

I did try everything you suggested, with seemingly unaffected results… until the most recent one, which is the first time the line made no appearance whatsoever. The only variable changed (yes, I remember, make one adjustment at a time (I realize the model itself is a variation, but up to this point it had been behaving exactly the same as all others)) was the rotation, which was 6°. No reason for choosing that number, other than it being the maximum permitted to remain within the boundaries of printable area. Is this enough to warrant further investigation of your possible belt adjustment theory?
EDIT: Never mind… it didn’t work with the original model.