topic Re: Punching a contoured hole in an irregularly-shaped part in Netfabb Forum

Punching a contoured hole in an irregularly-shaped part

Anonymous — Sat, 10 Apr 2021 22:36:28 GMT

Hi. I'd like to take a flat part I created in Netfabb by modifying an existing STL, and further modify it. Specifically, I'd like to cut a hole in it, the edge of which follows the part's outer contour, but is offset by a specified distance toward the part's center.

The attached image should help make this clear. I want the cut to follow the red line (all the way around the part), which is offset from the part's edge by 1.5 mm. I'm interested in saving the portion that is attached to the existing edge. That is, I want to save what is in the direction that the red arrows are pointing. I think of it as a 'frame' that has the outer contour of the part and is 1.5 mm wide.

I've fiddled with the Generate Shell command, but I don't think that'll do it. (The part was actually created by generating a shell 1.5 mm thick in the original 3D part, then slicing off the slab shown, which is also 1.5 mm thick.) I could well be wrong about this, since I don't understand all the options available in the Generate Shell command.

Would appreciate guidance or suggestions.

Thanks.

Re: Punching a contoured hole in an irregularly-shaped part

steffen_anders_adsk — Mon, 12 Apr 2021 08:18:03 GMT

Hello, @Anonymous,

Welcome to the Netfabb forum!

The functions in Generate Shell address hollowing and offsetting, as in, generating new meshes with constant surface distance from the original. (Ideally, but of course that's not possible due to discrete nature of triangulation)

If you want to manually stencil a piece from a mesh, remember that in Netfabb you work on triangles, not on solids. All you have to do is remove triangles and close the holes, meaning, to connect the now open borders with new triangles. Since you already seem to have the area to be removed triangulated separately, simply delete them in Repair, add "pilot" triangles where the contour changes, and close the remaining holes, similar to the advice in this post: https://forums.autodesk.com/t5/netfabb-forum/splitting-large-stl-and-shelling-for-printing/m-p/7565230/highlight/true#M45

Alternatively, you could extrude the triangles in question negatively beyond the other side …

… and then resolve the self-intersection so created:

This has the advantage of having to select the triangles only on one side.

Best regards,

Steffen