CNC Mill Tool Marks / "Swirl Pattern"

[Bob Loblaw]

When a metal part comes fresh out of the CNC mill, flat faces will have this familiar "swirl" pattern in a variety of different orientations, depending what cutting path the tool made.
What would be the best way to go about making this texture? It's quite hard to find an image good or large enough to use as a texture map.
Any way to do it procedural?

[Eugen Fetsch]

This patterns are very unique. One way I could think of creating those patterns proceduraly, would be exporting the finishing G-code to DXF, then convert DXF to SVG and use the SVG paths to drive a brush stroke to paint the pattern to a png.
It's not the simplest workflow, but if you have do do it very often, it makes sence to create such pipeline. G-Code to DXF or SVG conversion will mostly lead to a linearized pattern - a G2/G3 arc will be converted to small lines. But programs like Inscape can smooth such pattern out and covert them back to a curve again. You'll loose accuracy through all the conversions but for the sake of visualization it should work charming.

[DriesV]

Hi Bob,

To achieve the anisotropic reflections of the machined paths, you will have to use a special texturing technique for the Generic material type. A graphics editor like Adobe Illustrator can be used to create a greyscale image texture to accurately drive the anisotropy of the Generic material.
Will Gibbons has an excellent tutorial on YouTube where he guides you through the process from scratch to achieve this exact look.

In the video description is a free download link for the project files. There is also a link for the full (paid) tutorial on Gumroad.

Dries

[DriesV]

The 'Stainless Steel Circular Brushed Simple' material in the KeyShot 9 Material Library is a good starting point for the basic setup.
For the machined paths texture, you basically have to pattern an angular gradient circle across the paths. Make sure the orientation of the gradient stays the same along the pattern.

Dries

[Eugen Fetsch]

Hi Dries, thanks for sharing. This tutorial is nice, but it doesn't answer the question about how to create such textures, especially how to create them proceduraly. Any suggestion on this?

[DriesV]

You cannot create these textures procedurally in KeyShot. You have to create it using Illustrator or alike.
I attached a simple example (Illustrator file, texture, scene and rendering).

I also attached a quick video capture of the steps in Illustrator (no audio!).

Dries

[Trixtr]

I looked for a long time to solve this as well in a simple fashion. No such luck. However the, tutorial from Will Gibbons is excellent to understand how it works.

I created my textures in Gimp instead, since I don't have Illustrator. I started with a screenshot of my part and used the contours of the pockets as "borders" for the pattern. These were then imported into Keyshot on the appropriate surfaces. Unfortunatelly it takes quite a bit of extra work, but the result is very nice.

[Bob Loblaw]

Thank you all for your speedy responses!

Can't believe I missed Will Gibbon's video on the subject...

Dries, your technique works beautifully, thank you for the detailed instructions and files.

Eugen, I like your idea of using the actual G-code to create patterns for the texture. Would be pretty painstaking, but should create very accurate results!

[Eugen Fetsch]

Big thanks Dries, for creating and sharing this! *thankyoubow*

It'is exactly what I've ment, but using the machine G-code as the "bending" path instead of drawing the pattern manually. The G-code approach is only interesting, when you need to do a series of different or complex parts. For single projects it's an overdo, for sure.

[DriesV]

I don't think the process of creating the texture is all that tedious.
The biggest effort is in creating the path contours, but once you have that, making the gradient pattern/blend is pretty straightforward.
In Illustrator, you could make an action to speed things up, avoiding clicks and mouse travel. Select gradient and path, run action, done.

Atached is a video capture with an example (no audio!).

Dries