I was trying to turn a detailed circuit board CAD into a mesh. I'm a hobbyist/enthusiast and also use Blender & Tinkercad, and wanted to make sure I had a space in an organic model large enough to fit the PCB. The PCB is Adafruit's Monster M4sk. https://grabcad.com/library/monster-m4sk-1
I could easily turn all the bodies into meshes. But when I tried to merge the meshes, Fusion would lock up and freeze then crash. I tried to reduce how many I merged at once, but it seems it crashes at any sizeable number (I stopped trying at 10 at once, because there's about 100 meshes, and less than that would take forever). I've done similar operations in the past, but it was always like 2 or maybe 3 meshes at once. It seems it can't handle many meshes at once.
Solution:
If the team can't fix, or decides it's not worth fixing, many mesh merges like this, I would suggest building in a limit of how many meshes it allows you to choose when attempting the operation.
Fusion
