4. FEATURES
WHAT FEATURES ARE
Core technology
Features have the following characteristics:
- Encapsulates definition
- Topology constancy
- Behavioral rules
- Attributes
User defined features
Features are: named entities that encapsulate
how geometry behaves using rules and attributes in addition to
their defining constraints and geometry
FEATURE BASED DESIGN EXAMPLES
A through hole using Boolean:
- Could be defined using a Boolean difference
operation and a cylinder of sufficient length
- If the part became thicker and the cylinder was not long
enough, the hole would become a blind hole
A through hole feature understands the rule that it must pass
completely through the part and will do so no matter how the part
changes
Fillets and chamfers: edge treatments
Changes can occur to either the part or the feature
ADDING A FEATURE
Selecting the feature
Choosing feature variables
Positioning the feature
Feature options
FEATURE BASED DESIGN ADVANTAGES
Have stand alone intelligence
Easier future changes to the model
Use terms familiar to engineers
Downstream processes can access feature definition
EXAMPLES OF FEATURES AND THEIR USE
USER DEFINED FEATURES
Critical for customizing
Should provide similar functionality as supplied features;
e.g. -
- Selection
- Altering variables
Should inherit from existing features (be trainable)
OTHER ASPECTS OF FEATURES
List of features
How users apply them to the model
How they maintain their "featureness"
User defined features
Feature reordering and why
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