Fro MDTools we have 2 type of plugs: threaded with Spot/Face and expander.
Plugs without spotface must be threated like Expander with respect to Assembly Rules.
Example of threaded plug cavity
Example of Expander cavity
In both cases, user must identify cavity STEP0. Below images show how plugs must be assembled on the 3d model.
Threaded plugs follow “Cartridge Valve” assembly rules.
In this section user is supposed to select
Top Face = non relevant here but you must select (select external plug face)
Bottom Face = mating plane, surface that will match cavity STEP0 plane
Axis = plug axis (thread cylinder axis)
It’s possible to select any planar face from 3d model instead of planes. In case face is not planar, you can create plane with cad commands and select them instead.
If plug is assembled bottom-up, flip bottom face plane normal by using dedicated commands in Inventor or SolidWorks.
Expander follow Expander Plug assembly rules. For MDTools 700 Series (Inventor) only bottom edge is required. MDTools 900 series for SolidWorks requires 2 constraints, Bottom Edge and Bottom Face, because of different 3D CAD engine mating management.