The tyWeld modifier can be used to weld vertices and cull overlapping faces of a mesh. It is especially helpful for welding/culling the interior faces of a mesh converted to tets with a tyMesher.
Weld vertices: controls whether vertices will be welded together by proximity.
Weld threshold: the maximum distance threshold between vertices in order for them to be welded together.
Remove isolated vertices: removes any vertices not connected to at least one face.
Open edges only: only vertices on open edges (edges connected to a single face) will be welded.
Cull overlapping faces: controls whether overlapping faces (faces whose verts are all coincident) will be removed from the mesh.
Overlap thresh: the maximum distance between vertices on two candidate faces in order for them to be considered coincident. If all three vertices are coincident, the faces are considered overlapping.