Slices inside a shape

Hej and thanks again for this great software!
I wonder if there is a way to have laser slices cut so everything is inside the original 3D shape?
My usecase: I’m making a foam liner (with a hot wire cutter) that will go inside a vacuum formed 3D shell - that means that the whole slices (that will be 10-20 mm thick) must be inside the outer shape, and conversely outside any protrusion. Hope that makes sense! Is there such a function that I have missed?

Hi @Fredrik_Falkman and welcome. Yes, this is possible. For laser cutting, the kerf is represented by the offset value under layers. This is typically a positive value to account for the width of the laser beam. For your use case, you can set a 0 or negative value to “inset” the cut path.

This is an example of positive vs negative values.

(ignore the “thin wall” setting – that’s not supposed to be there and will be patched shortly)

Thanks for the quick and kind reply!
That seems to work fine for a concave shape, but I need it to take care of a concave shape with a convex one inside.
Here I have tried it and the resulting foam slices would go inside the circular convexity in the middle/bottom:

I have also tried to use a feature script called FS Slicer, which seems to put half of each slice on the inside and half on the outside:

The effect I’m after is this:

Annoying that I cant find the right words to explain this!


I get what you’re trying to accomplish. The offset method I recommended is not designed for this. I’ll think on it and see if I can come up with a solution.

Thanks! Much appreciated!

Would you - ore someone else here! - by any chance know what the principles that we’re discussing would be called? “Up to surface”, “mid-surface”, “past surface”?

A method that would work would be to take a “slice” of the and bottom of the desired cut-out piece and do a boolean intersection of those poly-lines. That would produce the most restrictive cut that would be guaranteed to fit within the 3d “body” shape