3D engraving - how do I convert CNC files?

[Jeffrey Aley]

Hi Folks,

I'm curious about 3D engraving. There are a number of free 3D files available on the 'net, which are targeted at CNC milling. For example, I just downloaded one that's in a .v3v format.
How does one convert such a file (or any other 3D format) for laser usage? Usually the renderer for the 3D image is side-lit. What we need (I think) is a 2D image where the lightness of the image corresponds exactly to the Z height (white at maximum Z height; black at minimum Z height).

Thanks,

-Jeff

[Jeffrey Aley]

Or maybe there's a way to use a 3D slicer to produce a series of files to be cut on the laser???? I'm still brainstorming...

[Gene Uselman]

What you need is a 3D Grayscale bitmap-
https://www.google.com/search?client=fi ... ale+images
It then engraves like a bitmap- sometimes 3 or 4 passes are needed. Russ has done a couple [at least] of videos on it.

[Pete Cyr]

I use aspire to create my models.
I have exported a picture of my models and import the into photoshop...create a gray scale, play with the saturation curve, then I perform as an @ 10 to 40% pwr with pretty good results

[Jeffrey Aley]

Thanks guys! I also found this https://community.glowforge.com/t/tutor ... aving/6659 .

I grabbed a couple of 3D models from Thingiverse to play with. The MeshLab seems to work as expected, but I haven't cut any of the resulting files on the laser yet.

I'll let you know what I find.

[Tim Mellor]

This sort of option might work for you. Requires some Fusion 360 (Free for most) skills and this add on is very simple to use and also a freebie. viewtopic.php?f=111&t=3901#p21921 edit just read you wanted to engrave not cut 3D models.

[Tim Mellor]

Now I have had a second coffee.

Other tools to try are

Blender https://www.blender.org/ I am a complete novice but it has way more power than I can handle at this stage.

Even the stock rubbish 3D viewer in Windows is of some use as it will export fairly his res screen captures of thew models and you can play with the lighting to a degree.

Fusion 360 does have a rendering environment but at this stage it is fairly limited and it is a CAD program not an artistic one.

Roughy Cat from https://www.thingiverse.com/thing:182091/files put through 3d viewer exported this screen capture then put it through Adobe or Inkscape to convert it to an SVG and play with it. Working with the limitations of STL's might need some additional smoothing/rendering to fix the polygon roughness.

[Jeffrey Aley]

Thanks for the various bits of advice. Here's the fundamental problem (from a technical perspective). When we have a 3D model and we look at it on the screen (which is a 2D device), the image is usually created using some form of raytracing. There is a mathematical model of a light source, and when the "light" hits the object it "reflects" back to the viewport, creating the image we see on the screen. The way it is rendered is intended to be realistic, with highlights and shadows, and usually the result IS realistic. (Those of you who are into 3D gaming are perhaps familiar with this).

So far, so good.

But the Laser doesn't care about a realistic rendering with highlights and shadows. We want the laser to carve an actual 3D object. So what it needs is a file that has light colors where the engraving should be shallow, and dark colors where the engraving should be deep. This is very different than the raytraced image we usually see. We need a rendering that I just learned is called "depth mapping".

Here's the cat after depth mapping. The parts of the cat that are closest to us are light; the parts farther away are dark. You can see this most obviously with the ears.

Annotation 2019-09-16 215558.png

Here it is with ordinary flat shading:

Annotation 2019-09-16 215733.png

Notice how the back of the cat, which is very far away from us, is actually lighter than the shadow under the cat's lip. It LOOKS good - but it's not what we need for 3D laser engraving.

Annotation 2019-09-16 220532.png

Here again, we have a visually pleasing appearance of the cat.

Annotation 2019-09-16 220458.png

And here's the depth-mapped version. The nose, which is closest to us, is the brightest part of the image. As parts of the cat are farther away, they are darker.

If I can perfect this technique, it means that many of the zillions of 3D images that are out there (for the 3D printer folks) can be 3D engraved using a laser.

Regards,

-Jeff

[Gene Uselman]

Jeffrey- I forgot to mention that on our lasers the process is *very* slow, more practical for RF lasers. You might want to try it before investing a lot of time.