Part Modeling > UDFs and Groups > Creating a UDF > About User-Defined Features
About User-Defined Features
A User-Defined Feature (UDF) consists of selected features, all their associated dimensions, any relations between the selected features, and a list of references for placing the UDF on a part. User-defined features can be subordinate or standalone. The UDF dialog box provides a running status of these UDF elements during UDF creation and modification.
Subordinate UDFs
A subordinate UDF gets its values directly from the original model at run time, so the original model must be present for the subordinate UDF to function. If you make any changes to the dimension values in the original model, they are automatically reflected in the UDF.
A model can have more than one subordinate UDF associated with it. Items in the family table of a subordinate UDF show the identifiers and symbols from the original model.
Standalone UDFs
A standalone UDF copies all the original model information into the UDF file. Because of this, a standalone UDF requires more storage space than a subordinate UDF. If you make any changes to the reference model, they are not reflected in the UDF.
When you create a standalone UDF, you have the option of creating a reference part by copying the original part from which the UDF is derived. The reference part has the same name as the UDF, with the extension _gp. For example, if you name a UDF radial_holes, the reference part is named radial_holes_gp.prt. A reference part displays UDF references and elements through the original features.
UDF Recommendations
Follow these recommendations for creating a UDF:
Make sure you have the desired dimensioning scheme.
Provide the necessary relations between the defining features before you create the UDF.
Although a reference part is not required for a standalone UDF, it is useful to have a reference part displayed when you place a UDF. The system highlights the dimensions to be entered and the reference information at the appropriate times during the UDF placement. If you have no reference part, the number of UDF elements you can modify is limited.
UDF Restrictions
When creating a UDF or copying features, you cannot mix features from the merged geometry group (created with the By Copy option) with features outside of this group.
Parameters not used in relations are not copied with UDFs to another part.
A UDF created in Part mode can be used in Assembly mode to create assembly features, as long as that UDF does not contain features that are not allowed for assembly features (such as rounds).
When you copy a group with an advanced round which contains user-defined transitions, the system removes user-defined transitions from the resulting feature. Redefine the round transitions in the new feature, as appropriate.
Dimension Types
You can create a UDF with the following dimension types:
Variable dimensions—Dimensions for which you will enter values when you place the UDF in a part.
Invariable dimensions—Dimensions that you will not change when you place the UDF in a part.
Table-driven dimensions—Dimensions and dimension tolerances for which values are given in a family table. Every instance in the family table has its own dimension values.