Polysurface and mesh to 3D print

Hello, i am new to Rhino and Grasshopper and I try to find a solution approach. My Professor gave me a complex geometry (the main geometry as an .stl file and the important surfaces that need to be exact as .step) and wants me to build a clean surface in grasshopper with it, so that I can 3d print the part. In the picture I postet you can see my tries to build a brep out of the .stl file and the .step files merged, but as you can see, its not very good. Further the brep still contains multiple groups after “Solid Union” and is very “edgy” and not round like a SubD for example. For the round parts that need to be exact, i want to build cylinders and just use “Solid Difference” with them, so that I have the correct measure. I dont want a correct solution for the task, just a tip or an idea how i can manage that. I tried multiple tips I found in this forum and read a lot, but nothing worked on my geometry. Can someone help me? Thanks!!

Since you are going to 3D print this object, you can turn the geometry from your step files into meshes right away. Make sure the geometry is closed.

The geometry in the STL, depending on whether it is a closed mesh or not, you could try to triremesh and mesh boolean union with the meshes from your exact geometry. In case you want to edit the geometry from the STL, quadremesh and then push / pull manually. Then mesh it again and boolean with the rest.

Depending on your print software, you might not need to boolean the meshes into one mesh yourself. Should you be using a formlabs printer, you could just load multiple STL files and Preform merges everything that overlaps into one print.

PS: I changed your title. The object you are going to create will never be built of ONE surface. The geometry in the STEP file is a polysurface. The STL files contains a mesh or meshes.

Can the TriRemesh or QuadRemesh components take this geometry as inputs?

I guess it depends on the accuracy required for the .step parts too.

There is no need to remesh the STEP parts.

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@martinsiegrist Thanks for your answer! Yes the mesh is closed. I used quadremesh on the stl file with settings i am happy with, then i used mesh to polysurface and solid union with the step parts… Additionally i did some solid differences with cylinders on the surfaces that need to be exact and that looks good as well. The only thing now is that the polysurface is not smooth. Is there a way to do it? Transform it back to Mesh and SubD for example? But then i will lose the important features i guess. Sorry if that is a stupid question, i still have to learn a lot about this process…

@martynjhogg Yes i can TriRemesh and QuadRemesh the .stl part. It looks OK but the step part is unusable if i quadremesh it.

When the mesh is closed, you don’t necessarily have to quadremesh it.

You could also keep the mesh as it is and only mesh the STEP parts with Mesh from Nurbs Object.

Then if really required mesh boolean or just mesh join, export an STL and open this in your print software.

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