How can I add placement etch lines for a lasercut when slicing geometry?

I’m planning on using the contour command to slice my geometry in rhino 5. However I don’t know how I can keep the lines of the previous piece, which I’ll need for constructing it physically.
I know I can split the geometry and then Make2d each part, but that will take too long for what I am trying to do, and I am wondering if there is a faster way.

Hello - what do you mean by this - do you want registration marks? You could add some intersecting geometry, say skinny cylinders,passing through the object normal to the cutting planes and include these in the Contours.


If you are making a topo map and you are looking to engrave lines on the previous contour level so that you can locate the next for assembly, this is what I would suggest:

  1. Put all your slice contours onto a layer by themselves. Name it, say, “Cut”, give it a distinctive color.
  2. Duplicate the layer and objects so that you have a second set of the same curves on a new layer. Name it, say, “Engrave”, give it a different color from “Cut”.
  3. Now, select all the curves on the “Engrave” layer and move them vertically exactly 1 contour increment.
  4. You now have a “Cut” and an “Engrave” curve on each level.

If you now want to spread out and flatten the curves for cutting, there are a number of ways, this is how I do it “manually”

  1. Make sure you can see at least the Top and Front views at the same time.
  2. From the Front view, select all the curves (Cut+Engrave).
  3. Call the command _Shear, pick two points in the Front view to create a vertical reference (like you did in _Contour) then, with Ortho off, start pulling shear line (and thus the curves) over to the left or right. In the Top view, you will see them spread out. When you see in the Top view that they are separate, left click in the Front view to set the shear where it is and complete the command. The curves are now spread out, but they are still at their original Z level, so -
  4. From the Top view, with the curves still selected, call _ProjectToCPlane>Delete input=Yes. The curves are now flat on the world XY plane.
  5. All you need to do now is arrange them on your boards for cutting.

Note that all of the above can be partially/mostly automated via scripts or Grasshopper.