An efficient workflow to follow when dealing with complex and/or dirty CAD models with numerous solid parts and numerous small details is as follows:
1) Delete all unnecessary parts
2) Delete any Bolts&Logos using the Geometry>Cleanup>Defeature tool
3) Make sure there are no big gaps/holes in the model. For this we usually use:
4)Surface mesh (will give better wrap results if meshing is done before converting to FE)
5)Convert to FE (default)
6)Use the Geometry>FE>Wrap>Cap tool to close the smaller holes/gaps.
Consider feature loops should be on.
Select all parts and close all pockets/gaps. Depending on the model the maximum width size may change but a good size would be 30-40mm.
7)Look for obvious bigger holes and close them again with the Cap tool but this time with the Nodes option in cap and manually selecting the region to cap.
8) Leak check with minimum leak size the same as the size of Wrapping. Make sure there is no leak and there is a closed volume.
9) Wrap the internal cavity of the model with Geometry>FE>Wrap>Run.
Wrapping Method: CAD wrap (generally gives better description of geometry)
Wrapping type: cavity
Choose enclosed seeds inside cavity
Quality cleanup Off
Maximum allowable gap based on the minimum feature/gap/hole size we want to retain.
10) Remesh with FE Geometry>Mesh
11)Use the Geometry>FE>Fix tool to fix the surface mesh quality.
Aspect Ratio and Intersection cleanup On
Select all faces-> fix
12)Validate (slivers will appear just set very small value and validate)
13)Volume mesh with "Retain surface mesh" On.