How to calculate and
display the mass properties (volume, surface area, and centroid)
of a model.
The Mass
Properties tool provides two ways of specifying the object
to measure:
- Solid – The
surfaces you pick represent the boundaries of a closed, solid object.
- Shell Interior –
The surfaces you pick represent the outside of a thin shell enclosing a
hollow space (for example, modeling a bottle with a single surface
of revolution). You specify the thickness of the shell.
Restrictions
To
get accurate statistics on an object, the following conditions must
be met:
- The surfaces must completely enclose
a volume. The edges of surfaces must meet within the tolerance value
set in the Mass Properties option window.
- The normals on all NURBS surfaces must
point out of the solid, and, when moving along a face boundary in
the increasing U direction, the face area must be to the left when
viewed from outside the solid.
or
The normals on all NURBS surfaces must point
into the solid, and, when moving along a face boundary in the increasing
U direction, the face area must be to the right when viewed from
outside the solid.
You can check the seam
between two surfaces by placing a Deviation measurement
on the seam. You can check the orientation of normals using the Reverse
Direction tool.
Show the mass properties
of a model
- Pick all the surfaces that make up the
model. Make sure the surfaces completely enclose the volume of the
object.
- Click the Mass Properties icon, or choose Evaluate > Mass Properties from
the palette.
When
the Mass Properties tool completes
its calculations, the Mass Properties window
appears, containing the following statistics about the object.
Label |
Description |
Formula |
Units |
Current unit of measurement (default is either centimeters
or millimeters, depending on which product you are using).
|
|
Area |
Area of the picked surfaces. |
|
volume |
Volume enclosed by the picked surfaces, or volume occupied
by shell surface with given thickness.
|
|
centroid |
X, Y, Z coordinates of the center of the object |
|
NoteIf
you are using a construction plane when you click the tool, the
calculations use the X, Y, and Z axes of the current construction
plane.
If
you change the options of the Mass Properties tool,
the window updates.