Newbe: Union between STL and new objects?

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Georg99
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Newbe: Union between STL and new objects?

Postby Georg99 » Thu Nov 06, 2014 11:06 pm

I am new at freecad: is it possible to modify imported STL-objects (eg. from thingiverse) with union/intersect/difference with solid made objects in freecad?
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NormandC
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Re: Newbe: Union between STL and new objects?

Postby NormandC » Thu Nov 06, 2014 11:18 pm

Only if you convert the mesh to a solid.

You need to switch to the Part workbench, then in sequence and from the Part menu:
  1. Create a shape from mesh
  2. Convert the shape to solid
  3. Optional: apply a refine shape to the solid (it will clean up the coplanar faces)
Once you're done, you can delete all the previous objects from the tree and only keep the last one.
Georg99
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Re: Newbe: Union between STL and new objects?

Postby Georg99 » Thu Nov 06, 2014 11:43 pm

Thanks I got it!
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quick61
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Re: Newbe: Union between STL and new objects?

Postby quick61 » Fri Nov 07, 2014 12:00 am

If for whatever reason it does not want to work that way, you still have one more shot at it by converting your current solid into a mesh and doing a mesh Boolean in the Mesh Design Workbench. I've found on several occasions, going the reverse has worked.

Mark
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jmaustpc
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Re: Newbe: Union between STL and new objects?

Postby jmaustpc » Fri Nov 07, 2014 5:47 am

a tip in addition to the other responses...

I am deliberately over simplifying this to get my point across clearly.....A mesh is "dumbed down" object compared to a shape. So it is easy to go from a shape to a mesh (to be overly basic, you pretty much just forget half the information). However the opposite is almost impossible, because to go from Mesh to Solid you have to "remember" all that data you lost, which is impossible, so you get an approximation/guess which can not, in most cases, be correct.


You can do Boolean operations with two mesh objects as Mark said, however you now need OpenSCAD to be installed on your system for this to work.
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shoogen
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Re: Newbe: Union between STL and new objects?

Postby shoogen » Fri Nov 07, 2014 11:54 am

+1 for Jim
And there is one thing I'd like note to platforms like thingiverse. There is a chance that the original author has the file in a proper CAD format. If he used a CAD program, he should be able to export a STEP file. If he used OpenSCAD it would make sense to, at least try to, import it directly. If the part was modeled in Design Spark Mechanical (or as I call it the Space Claim demo version) you might get to extract the ACIS (SAT) data from the .rsdoc file. Only if the original part was designed in mesh modeler (Blender, Wings3d, 3dmax...) or meshed form a point cloud you are stuck with the STL.
Thingiverse allows you to contact the author.

The conversion only works (well) for meshes with a low triangle count.