Magical mid lines - how to remove?

Anyone know why I am seeing mid-lines on the surface of my drawing, and how I can get rid of them so they don’t appear when I try to export a flat file for lasercutting? See the red arrows on the uploaded file.

Select the surface, and in properties, uncheck “show isocurves”… But why surfaces for laser cutting? Normally all you need are curves. If so, DupBorder the surfaces and hide/delete the surfaces.


Many thanks Helvetosaur. I wanted to have a 3D object for my benefit envisaging it, and then flatten it for the lasercutter.
Also I’m fairly new to this game, and very green at Rhino. This would actually be my first Rhino-drawn object to get made!

try with Make2D then to get only the curves of your 3d object to cut it

OK, in that case, I would run DupFaceBorder on the top or bottom surface to get all the edges as curves, then put that on a separate layer and use ProjectToCPlane to make sure the curves are at Z0. Then send the curve file to the laser cutter.

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Thanks Diego, Make2D worked nicely and puts it into a new layer, then I deleted the Default layer where the 3D object resided and was left with just the 2D version to save as a different file.

And thanks again Helvetosaur, that also worked nicely, and I found the command CopyToLayer (created a new layer in the process) was useful to run straight after DupFaceBorder while the curve objects were still autoselected, prior to running ProjectToCPlane. In my case I wanted to say yes to the Delete Input Objects option. Learning lots - love the support here!