Model-Based Definition > Model-Based Definition > Working with Model Properties > Units > Tip: Rules for Modifying Units
Tip: Rules for Modifying Units
Modifying the units can invalidate your relations, as they are not scaled along with the model. Other non-parametric features, such as cosmetic, or IGES models are also not scaled with the change of units.
A part can have only one set of units.
All parts default to inches and pounds (unless otherwise set by the configuration file options pro_unit_length and pro_unit_mass).
The initial units for an assembly are those of its base component. If, however, the units of the base component have been changed, the assembly units do not automatically change. You must re-specify the units of the assembly.
You cannot change the units of an assembly that contains assembly features which intersect a part.
User-defined parameters have no units; therefore, include appropriate conversion factors in relations.
Cross-sections have no units.
If you delete a custom measurement units system, make sure the system is not the selected system for the current part.