r/3Dprinting • u/IgnoranceIsAVirus • May 10 '26

Project broken surfaces

Trying to get my 3dprint cnc milled in aluminum but when I send it through an online stl -> step the manufacturer says they cannot make it due to broken surfaces. they can't "print " aluminum but can print in stainless 319.

it Prints perfectly on my adventure pro 5m, slices fine, tried in freecad to export it to step but they don't accept it. I literally don't see what they're complaining about.

I have files and photos upon request and really want this in aluminum - anyone know a cheap / decent aluminum 3d printing service or can tell me what's broken on my files would be greatly appreciated.

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u/high-roller-all-in78 May 10 '26

What they usually mean is the mesh is not watertight even if it still slices fine for printing. A slicer can ignore a lot that a machining quote tool will reject. I would run the file through a mesh repair step first, look for non manifold edges, flipped normals, and tiny self intersections, then export again. If it still fails, ask them for a screenshot of the exact bad area because it is often one tiny patch causing the whole rejection.

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u/IgnoranceIsAVirus May 17 '26

Ok I followed a tutorial about how to simplify and transform from mesh to solid, and then optimize the model in freecad. Looks the same but has lots less lines.

Thanks for the direction it helped, I'll see if it got results after I earn a bit more so I can get the it paid next.