After creating a local coordinate system, you can further designate it as being associative or non-associative using the properties of the Origin category in the Details.
An associative coordinate system is joined to a geometry or mesh scoping throughout preprocessing. Therefore, its position and orientation can be affected by geometry updates, part transformation, as well as through the use of the tool (for joints). However, the coordinate system maintains its position throughout the solution process regardless of changes to the geometry as a result of loading.
A non-associative coordinate system is independent of any geometry.
Specify Associative Coordinate System
To define the origin for an associative coordinate system:
Select an existing Coordinate System object or insert a new object.
Set the Define By property to either Geometry Selection (default) or .
For a Reference Coordinate System attached to a joint, use the Orientation About Principal Axis category to make the coordinate system associative.
Tip: You can automatically specify the Geometry of a Coordinate System object by first selecting geometry or mesh entities and then inserting a new Coordinate System object.
Specify the origin using one of the following methods:
- Geometry Selection
Select the desired geometry or mesh entities.
Select the Geometry property field and make your selection.
Click .
A coordinate system symbol is displayed at the centroid of the selected entities. The application calculates the centroid using a weighted average based on the selected entity type:
Solid bodies and solid elements: volume.
Surface bodies, faces, surface elements, and element faces: area.
Line bodies, edges, and line elements: length.
Note: To create a coordinate system on a Line Body, you need to select one or more edges, vertices, nodes, or elements so that the origin is placed at the centroid of the selections.
- Named Selection
Select a user-defined Named Selection from the property drop-down menu.
Note: The origin calculated for an associative coordinate system may differ slightly from the centroid reported by Discovery, SpaceClaim, or other CAD applications. Mechanical determines the origin based on the scoped geometry and its internal geometric or tessellated representation. For cylindrical faces, the origin is placed on the cylinder axis at the face centroid location. For a full cylindrical face, this location coincides with the true geometric centroid. To preserve a CAD-defined coordinate system location, create the coordinate system in the CAD application and import it into Mechanical. Alternatively, use a non-associative coordinate system and enter the location directly using the Origin X, Origin Y, and Origin Z properties.
Specify Non-Associative Coordinate System
To define the origin for a non-associative coordinate system:
Set the Define By property to Global Coordinates.
Define the origin using one of the following methods:
Select a point on the model using the Hit Point Coordinate option.
Select vertices, nodes, element faces, or elements to calculate an average location.
Enter coordinates directly using the Origin X, Origin Y, and Origin Z properties.
- Select a Point on the Model
Select the Location property field.
Select the Hit Point Coordinate (
) option on the Graphics Toolbar. This option displays coordinates as you move the
cursor across the model.Select the desired origin location on the model.
Click .
- Select Geometry or Mesh Entities
Select the Location property field.
Select the desired geometry or mesh entities (Vertex, Node, Element Face, or Element).
Click .
- Enter Coordinates Directly
Enter values in the Origin X, Origin Y, and Origin Z properties.