Thiết kế flash - Parametric modeling

Parametric ModelingAn IntroductionParametric ModelingFeature-based modelingConstraint-based modelingAlso called:Parametric Modeling uses parametric constraints to define and easily modify part features, and to create relationships between these features in order to create intelligent part models. These virtual parts can then be combined to form assembly models.FeaturesBasic unit of a parametric solid modelA feature is a 3D shape. Parts are formed by their featuresModel features mimic actual design & manufacturing features (e.g., fillet, counterbore hole, draft angle)2 basic kinds of model features:Sketched (e.g., extrusion, revolution, loft)Built-in (e.g., hole, chamfer, fillet, shell) No sketch requiredParametersA parameter is a named quantity whose value can be changedFor example, d0 = 10Parametric dimensions: Control feature sizeAre easily modified  feature geometry changesEstablish relationships across features, parts, assembliesFor example, d0 = d1/2ConstraintsA constraint is a mathematical requirement placed on the geometry of a 3D modelKinds of part constraints:Dimensional – limits feature sizeGeometric – limits feature shape (e.g., parallelism tangency, colinearity) Assembly constraints (e.g. mate, insert)Parametric Modeling CharacteristicsModel flexibility; easy to update, modifyReflects design intent (i.e., the purpose or function of a feature)Model history viewable in feature tree (similar to CSG)Drawings generated from parametric model are linked to model  associativeRelationships between parts are maintained in database  assembly modelingTop–Down: Product DevelopmentProductAssemblySub-assemblyPartFeatureBottom-up: Part ModelingDefine sketch planeSketch the geometrySome geometric constraints added automaticallyAdd other geometric constraintsAdd dimensions  fully constrainedCreate the (base) featureRepeat 1 to 5, adding other (sketched and/or built-in) featuresSketchRough sketchSome geometric constraints are automatically appliedGeometric ConstraintsCan display constraintsApply additional constraintsDimensional ConstraintsAdd DimensionsProfile is fully constrainedFeature Generation - ExtrudeBuilt-in FeaturesFeature TreeParametric ModelingNada MasAn Introduction