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In this chapter, students will be able to understand: Create simple extruded solid models, understand the basic parametric modeling procedure, create 2-D sketches, understand the “shape before size” design approach, use the dynamic viewing commands, create and edit parametric dimensions.
Parametric Modeling An Introduction Parametric Modeling Also called: Featurebased modeling Constraintbased modeling 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 Features Basic unit of a parametric solid model A feature is a 3D shape. Parts are formed by their features Model 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) Builtin (e.g., hole, chamfer, fillet, shell) No sketch required Parameters A parameter is a named quantity whose value can be changed For example, d0 = 10 Parametric dimensions: Control feature size Are easily modified feature geometry changes Establish relationships across features, parts, assemblies For example, d0 = d1/2 Constraints A constraint is a mathematical requirement placed on the geometry of a 3D model Kinds of part constraints: Dimensional – limits feature size Geometric – limits feature shape (e.g., parallelism tangency, colinearity) Assembly constraints (e.g. mate, insert) Parametric Modeling Characteristics Model flexibility; easy to update, modify Reflects 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 associative Relationships between parts are maintained in database assembly modeling Top–Down: Product Development Product Assembly Subassembly Part Feature Bottomup: Part Modeling Define sketch plane Sketch the geometry Some geometric constraints added automatically Add other geometric constraints Add dimensions fully constrained Create the (base) feature Repeat 1 to 5, adding other (sketched and/or builtin) features Sketch Rough sketch Some geometric constraints are automatically applied Geometric Constraints Can display constraints Apply additional constraints Dimensional Constraints Add Dimensions Profile is fully constrained Feature Generation Extrude Builtin Features Feature Tree Parametric Modeling An Introduction Nada Mas .. .Parametric Modeling Also called: Featurebased modeling Constraintbased modeling Parametric Modeling uses parametric constraints to define and easily modify part features, and to create relationships ... A parameter is a named quantity whose value can be changed For example, d0 = 10 Parametric dimensions: Control feature size Are easily modified feature geometry changes Establish relationships across features, ... Profile is fully constrained Feature Generation Extrude Builtin Features Feature Tree Parametric Modeling An Introduction Nada Mas