# Dialog: CAD-Line | Mass Properties tab

## CAD-Line | Mass Properties tab

MechDesigner has three sources for its Mass-Properties:

 • Mass-Properties that are user-defined on the CAD-Line.
 • Mass Properties imported to a CAD-Line with a SolidWorks document.
 • Mass Properties that are derived from Profile/Extrusions on a Part

### Mass Properties tab

Separators

 Mass : [kg] Centre-of-Mass: X–axis [mm] The X-axis is along the CAD-Line, with [0mm] at the start-Point of the Part. Centre-of-Mass: Y–axis [mm] The Y-axis is at +90º from the CAD-Line, with [0mm] at the start-Point of the Part. Inertia If you define the mass on its position, then the mass will be a Point-Mass. Its mass distribution is defined its Radius-of-Gyration [mm] or Moment-of-Inertia [kg.m2] Note: Units: kilogram.metres2 NOT kilogram.millimeter2

If you enter Moment-of-Inertia, then with the Mass, MechDesigner calculates the equivalent Radius-of-Gyration

If you enter Radius-of-Gyration, then with the Mass, MechDesigner calculates the equivalent Moment-of-Inertia

Parallel Axis Theorem

MechDesigner uses the Parallel Axis Theorem to calculate the Moment-of-Inertia, Io , about the Part's rotational axis:

I0 = IG +M.h2 where h is the distance from the Centre-of-Mass to the rotational axis

When you import a SolidWorks document onto a CAD-Line, you can also import the SolidWorks Mass-Properties

Button IMPORT / UPDATE Mass Properties FROM THE ACTIVE SolidWorks DOCUMENT

Make sure that the SolidWorks' active document is the model on the CAD-Line.

 Mass : [kg] The Mass of the active SolidWorks document SolidWorks Centre-of-Mass : X-axis: [mm] The distance along the X-axis from the CAD-Line start-Point to the Centre-of-Mass. Centre-of-Mass Y-axis [mm] The distance along the Y-axis, from the CAD-Line start-Point to the Centre-of-Mass. Moment-of-Inertia (C.o.G) [kg.m2] The Inertia with respect to the Centre-of-Mass

Button Remove SolidWorks Mass Properties

Total Mass Properties:

The Total Mass Properties for ALL CAD-Lines in one Part.

EXPLICITLY: the Total Mass Properties include, for each Part, ALL of those:

 • Mass and Mass-Properties as calculated for ALL Profile/Extrusions in the Part
 • User Mass-Properties as defined for ALL CAD-Lines in the Part
 • SolidWorks Mass-Properties as defined for ALL CAD-Lines in the Part

NOTES:

Parallel-Axis Theorem

Inertia about Part's Rotational-Axis = Total Inertia about Centre-of-Mass + Mass × (Distance to Part's Rotational-Axis)2

Relationship between Moment-of-Inertia and Radius of Gyration