You can use the system parameter mp_density in a relation to specify the density of a part. This density value is used for calculating mass properties. If you change the material density in a part, the system updates the mp_density value in relations.

If mp_density is being driven by a relation and you change the relation, the density of the part is updated to the new mp_density value when the part is regenerated. In addition, if a material was assigned to the part at the time of regeneration, the material density is also updated to the new mp_density value.

If you change the density of the part using the Density field in the Setup Mass Properties dialog box, mp_density is updated immediately. If a material has been assigned to the part, the density of the material is also updated immediately.

If a material has been assigned to the part and you change the density of the assigned material using the Material Definition dialog box, the density of the part and mp_density are both updated immediately.

In both of these cases, any values that are dependent on mp_density are updated after regeneration.