Parametric Modeling

1
Parametric Modeling
An Introduction
2
Parametric Modeling
Also called

• Feature-based modeling
• Constraint-based 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.
3
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)
• Built-in (e.g., hole, chamfer, fillet, shell)
• ? No sketch required

4
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

5
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)

6
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

7
TopDown Product Development

• Product
• Assembly
• Sub-assembly
• Part
• Feature

8
Bottom-up 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
  built-in) features

9
Sketch

• Rough sketch
• Some geometric constraints are automatically
  applied

10
Geometric Constraints

• Can display constraints

• Apply additional constraints

11
Dimensional Constraints

• Add Dimensions
• Profile is fully constrained

12
Feature Generation - Extrude
13
Built-in Features
14
Feature Tree
15
Parametric Modeling
An Introduction

• Nada Mas