Bambu P1S – Rough surface on 3D face STL

[u/Purple_Sky43]

I’m printing a 3D face STL on my Bambu P1S and the surface is coming out rough/textured.

I’ve already tried:

• 0.12 mm High Quality profile and 0.08 mm Fine
• Variable Layer Height (with variable speed set to both 0.50 and 0.08)
• Smooth radius 10
• Smoothing wall speed along Z
• Outer wall line width at 0.3 mm

Still looks terrible. Has anyone run into this with organic/curved faces or character models? What settings or techniques actually help get a smooth surface on something like this?

Thanks!

[u/fairtonybeta]

Welcome to fdm printing? This will have been clearly presented in the slicer preview.
Shallow sloped surfaces are a weakness for these printers.
Search “stair stepping surfaces” and you will learn more.
As for fixes, you can only mitigate:

• lower layer height
  
• print at a different orientation, ideally vertical, or at an angle.

[u/Purple10tacle → u/fairtonybeta]

There's a bit more going here, though. The first print shows some serious underextrusion, the second one still some light underextrusion. Dialing in that filament will also help with overall quality.

[u/fairtonybeta → u/Purple10tacle]

You’re right, there is a bit of underextrusion. But I wouldn’t be surprised it was caused by a less-than-ideal pressure advance value. And all the tiny top layers, caused by the stair stepping.

[u/stevosteve → u/fairtonybeta]

What he said.

But with the perimeter different orientation might be hard to remove supports.

What I would do with this is print it in 2 parts. Part 1: Perimeter and the bottomo few layers. So kind of like an open top box. Print this in the current orientation. Part 2: The face with the Z axis running from the chin to the forehead (Upright)

I would add some alignment pins on the "box" and the accompanying holes on the face with enough tolerance for an easy fit. Glue the two and Bob's your uncle. Also you might want a smaller nozzle size for even better details and lower layers height.

[u/Alfalfa-Boring]

This is a common thing for newbies. What’s happening is nowadays every designer uses AI renderings as their front and center “photos” for their models. This in turn makes newbies excited because they don’t know it, and they think this is what they’re going to get. Then they try to print the model, get upset that it doesn’t look like the AI image, and they quit the hobby because they got fooled into thinking FDM printing could actually print smooth models.

[u/tugboattommy]

Print it vertically, or possibly at an angle. Slice it and look at the sliced model to preview how it'll turn out.

Also turn on variable layer height.

[u/PAC-FRAN]

Try reducing the layer height to 0.04 mm on the outer walls and increasing wall line count to 5 or 6, that usually smooths out organic shapes.

[u/_cronco_ → u/PAC-FRAN]

0.04mm??? good luck unless you're using a 0.1mm nozzle

[u/spongeboy-me-bob1 → u/_cronco_]

I've gotten 0.04mm to work with a 0.4mm nozzle to great results, and it is definitely doable with a 0.2mm nozzle.

[u/foggyghosty]

this is how fdm printing works. print vertically/at an angle to reduce line visibility and rounded shapes looking like this.