TN-007: Surface Texture for Better, Cheaper 3D Printed Parts

Adding a surface texture to a 3D printed part is one of the cheapest ways to make it look better. Texture hides layer lines, up-skin variation and sprue witness marks, and once vapour polished it can look stunning, much closer to a textured moulding than a printed part. It can also take whole steps out of the process. We recently halved the price of one customer's parts by adding texture and removing the need to hand finish and paint them.

By Jerry Sutton, founder and engineer, Incremental-AM.

The short version

Texture hides print artefacts. A fine, even texture scatters light, so stair-stepping, slight finish variation and witness marks disappear.
It must be real geometry. CAD appearances and decals don't print. The texture has to be modelled into the surface.
Make it deep enough. Aim for about 0.3 to 0.6 mm deep, so it survives bead blasting and vapour polishing.
Keep it off functional faces. No texture on mating, sealing or toleranced surfaces.
Texture plus vapour polishing gives a satin, moulded look and a pleasant feel, with no paint.
We can add it for you. Send a STEP file and tell us which faces to texture.

1. Why texture works

A smooth surface shows everything. Every layer step on a shallow slope, every small change in finish between up-skin and down-skin, and every witness mark from a joining sprue catches the light. The usual fix is to fill, sand, prime and paint by hand, which is slow, expensive and hard to repeat across a batch.

A fine, even texture breaks up the reflections. The eye reads the texture rather than the small defects underneath, so the same print looks clean and consistent straight from the machine.

Sketch comparing a smooth MJF part, where layer steps, patchy finish and a sprue witness mark all show, with the same part textured, where the texture scatters light and hides them

2. Case study: half the price, no paint

A customer came to us with a cosmetic part that was being printed smooth, then filled, sanded and painted by hand to hide the layer lines. The finishing was most of the cost, and every batch looked slightly different.

We added a fine texture to the visible faces, then dyed and vapour polished the parts. The hand finishing and painting went completely. The part price halved, the lead time shortened, and every batch now comes out the same.

3. Texture depth and size

These are good starting points for MJF PA12. We are happy to advise on your part.

Depth: about 0.3 to 0.6 mm. Shallower than about 0.2 mm tends to get lost in the natural grain of the surface and is largely polished away.
Feature size: keep peaks and dimples at least about 0.5 mm across, with a spacing (pitch) of about 1 mm or more. Finer than that blurs into the surface.
Shape: rounded, open textures (stipple, leather grain, soft knurl, hex) clean and polish better than deep, narrow grooves, which can trap powder.
Thin walls: texture removes material. Keep at least 1 mm of solid wall under the deepest point of the texture.
Consistency: use the same texture scale across all show faces, so the part reads as one surface.

4. Texture and vapour polishing

Vapour polishing slightly melts and smooths the surface. On a smooth part it gives a gloss finish. On a textured part it softens the peaks, giving a satin finish with depth that looks and feels like a quality moulding. Combined with black dye it is our favourite cosmetic finish.

Because polishing rounds the peaks, start from a texture deep enough to survive it.

Sketch of texture profiles before and after vapour polishing: a texture about 0.1 mm deep polishes almost flat, while one 0.3 to 0.6 mm deep keeps its shape with softened peaks

Raw (bead blasted): matte, hides marks well, but can feel slightly dry.
Dyed: the texture helps the colour look even across the part.
Vapour polished: satin, soft to the touch, easier to clean and better sealed. See TN-005.

5. Where not to texture

Mating faces, snap fits and anything that slides or locates
Sealing faces and O-ring grooves
Toleranced or inspected dimensions
Small text and logos (keep a smooth border around them so they stay legible)
Faces where witness marks or the up-skin will sit anyway and nobody will see

Leaving a small smooth margin round the edge of a textured face also gives a crisp, deliberate look.

6. How to add texture

The texture must be true 3D geometry in the file. Appearance textures, decals and rendering materials in CAD look great on screen but are not exported, so they will not print.

In CAD: some packages can turn an image texture into real geometry, for example SolidWorks 3D Texture. Others need a dedicated tool.
Dedicated tools: nTop, Materialise 3-matic and similar engineering tools apply textures to selected faces with good control over depth and scale. Blender's displacement modifier also works for one-off cosmetic parts.
File format: textured parts are meshes with a lot of detail, so send a high-resolution 3MF or STL. Files can be large, so check that the texture is still there after export.
Or let us do it: send your STEP file, mark the faces to texture and tell us the look you want. We apply the texture at the right depth for the process and finish.

What to send

A STEP file (we texture it), or a textured 3MF or STL
The faces to texture, and any faces that must stay smooth
The look you want: fine stipple, leather grain, knurl, or a sample or photo
The finish: raw, dyed or vapour polished
The quantity, and a sentence on what the part does

Not sure if texture would help your part? Send it over and we will tell you. Our design advice is free, and you can price parts straight away with our instant quote.

TN: 007 - Surface Texture for Better Looking, Lower Cost 3D Printed Parts