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How to fill an STL form in "skin"?

Message 1 of 6
737 Views, 5 Replies

How to fill an STL form in "skin"?

Objective: to machine a relief shape (3D machining) as in the photo.


The source: a stl, which turns out to be a "skin", not closed and which also has the distinction of being hollow (the fish) where I would like to obtain relief.




The idea was to get a full body (close the base) and combine it with another full shape (a rectangular base of the same dimensions ) to obtain an inverted shape, this time in relief. I should also reduce the number of faces to less than 5000 to use it in Fusion 360.
In size, the final object will be 300 mm at the longest.

Can we do that with Meshmixer ?

After this, I will use Fusion 360 and manufacture to mill wood.

Message 2 of 6
in reply to: jive34500

Yes, all this can be done in MM. But you might loose some details doing such a harsh reduction.

I recommend:

  1. Scale it to the final size first to get an idea of the "depth" of the shell's profile at its final size. You need that value to add some extra thickness extruding it.
  2. Hit Ctrl+A (Cmd+A on MAC) to SelectAll and run Edit/Reduce. Set its ReduceTarget to TriangleBudget and set TriCount to something below Fusion's max. density (e.g. 45k). Disable PreserveBoundaries.
  3. Now run Edit/Extrude on this selection. Set EndType to Flat and some positive Offset (bigger than the shell's "depth" - I did 30mm). This flips the shell automatically.
  4. Now you'll need to reduce the surfaces generated by extrusion. Select them by double clicking the new group and run Edit/Reduce. Set its ReduceTarget to TriangleBudget and set TriCount to 5k. Enable PreserveBoundaries.
  5. Now you might EDIT/GenerateFaceGroups at high Angle- and SizeThreshold to select the side and bottom surfaces and do Deform/Smooth...
  6. Finale add the plane object from the file menu. Extrude it and Scale it using EDIT/Transform to join it with BooleanUnion to the first object.

Result without the base cuboid attached.

Gunter Weber
Triangle Artisan

Message 3 of 6
in reply to: MagWeb

A big thank-you. I just quickly visualized it in the Prusa Slicer, that's exactly what I was looking for. I will dive into this procedure to understand the logic, because I am starting with Meshmixer. Regards.

Message 4 of 6
in reply to: MagWeb

Is even the CAM portion of Fusion limited to 45K triangles?

Message 5 of 6
in reply to: hfcandrew

Yes, Manufacture accepts to calculate with more than 45 k.
In Meshmixer, stl reduced to 60 k, then extruded and saved (weight 56,691 KB)

Truite 60 k MM.jpg

Operation 1 to 4: ok.
Operations 5 and 6: I did not manage to follow the procedure.
Import mesh in Fusion 360 then direct to Manufacture.

Truite simulation.jpg

I was able to calculate the toolpaths and launch the simulation (3h30 machining)

Message 6 of 6
in reply to: jive34500

Step 5 is meant to smooth the contour sides of the ellipse:

In EDIT/GenerateFaceGroups adjust the sliders to get a single group there

Ohne Titel.png

In SELECT select that group by a double click and run Deform/Smooth:

Ohne Titel 2.png

Step 6 is to add a rectangular base shape. You might drag a cube from MESHMIX/Primitives to empty space. Use EDIT/Transform to scale and move it to the desired size and location. Now activate both objects (press Shift and click to activate the second object) and do EDIT/BooleanUnion to weld them to one...

Gunter Weber
Triangle Artisan

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