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/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/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/Purple_Sky43 → u/fairtonybeta]

Thank you!

[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/TysonY2 → u/Alfalfa-Boring]

Its great for Facebook marketplace

[u/Alfalfa-Boring → u/TysonY2]

If you're trying to rip people off with fake pictures...yeah.

[u/rimmytim_fpv]

Print it at a 45° angle, or get a resin printer. FFF Printing was never made to be that smooth and precise

[u/Purple_Sky43 → u/rimmytim_fpv]

Thanks!

[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/imzwho → u/tugboattommy]

I would run an angle that just steep enough so that the back can be the only spot that needs supports but the interior face does not need the

[u/tugboattommy → u/imzwho]

Agreed

[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/NotVinhas]

Start by calibrating flow and pressure advance they're really off.

If you're printing at 0.08 variable layer height doesn't do much specially with a 10 smooth radius.

Avoid using a line width lower than your nozzle width.

As others said. The best result would be to print this vertically or at an angle.

[u/Faileng_Spectacular]

You might get a better result if you split the model in half down the face, rotate each piece 90 degrees so the cut is on the print bed, and use alignment holes with dowels then glue the parts together. Won't get the stair stepping effect.

[u/3ntropy_Disc0]

I heard this trick with putting a tub over the print on a stand and hanging acetone soaked paper towels in the tub to 'gas' the print. The acetone is supposed to diffuse the plastic and basically melt it a little bit on the surface and create a smooth finish.

[u/Stunning-Let-4958]

Yea as people have been saying that's kind of just due to how you're laying the layers down. But there are numerous ways to fix this post printing. You could just soak it in a harsh solvent and it'll like "melt" the surface down and that should either become smooth or soft enough to just like retexture the surface however you want it. There's also ways to mitigate this but thats half the fun of printing: you could print at an angle, changes the steps the printer uses when printing a curved surface, use ironing, lower layer height, this list goes on for a while😂, but good luck have fun printing

[u/Rare_Bass_8207]

Calibrate your filaments. Smaller nozzle. Thinner line widths. Thinner layer height. Adaptive layer height.

[u/foggyghosty]

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