Parametric Sketching

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Parametric Sketching
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Motivation

• Solid primitives not typically supported in
  parametric modelers ? must create a 2D profile,
  then sweep

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Feature Creation Procedure

• Choose sketch plane, either a
• Default work plane
• Planar face of existing feature
• Work plane
• Rough sketch
• Some geometric constraints applied
• Add/delete geometric constraints
• Parametric dimensioning
• Feature creation
• Repeat 1 - 5

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Construction Geometry

• Geometry created as part of the parametric
  modeling process that does not represent actual
  part geometry. Includes
• Work planes
• Work axes
• Work points

• Construction geometry appears in feature tree

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Default Construction Geometry Inventor

• Work planes mutually perpendicular
• YZ
• XZ
• XY
• Work Axes
• X (red)
• Y (green)
• Z (blue)
• Work Point
• Origin of WCS

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Rough Sketch

• Parametric sketching imitates actual sketching
  process ? rough, approximate

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Sketch Plane Views
View normal to sketch plane
Isometric View
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Geometric Constraints

• Typical constraints include vertical,
  horizontal, collinear, concentric, tangent, etc.
• Inventor constraints

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Display Geometric Constraints

• Software includes option to show constraints

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Add/Delete Constraints

• User can manually (explicitly) add constraints

concentric
tangent
equal
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Parametric Dimensions

• Add parametric dimensions to fully constrain
  profile
• Each parametric dimension has two components
• Numerical value
• Name

Fully Constrained Sketch
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Parametric Dimensions - 2

• Default parameter names (e.g., d0) can be changed
• Equations can be used to generate parameter value

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Under and Over-constrained Sketches
Angle not necessary
Vertical position of hole not specified

• Under-constrained

Over-constrained
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Parametric Sketching