Sketching is an important tool for quickly and efficiently communicating design ideas. It is a particularly useful tool early in the design process when several ideas are being explored. A fundamental technique within most parametric modeling programs is to sketch 2-D features then use a 3-D construction operation, such as extrude, revolve, or sweep, to create a 3-D model.
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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
1. Choose sketch plane, either a:
Planar face of existing feature
1. Rough sketch
1. Add/delete geometric constraints
2. Parametric dimensioning
3. Feature creation
4. 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 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
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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
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 Overconstrained
Sketches
Underconstrained Overconstrained
Vertical position of
hole not specified
Angle not necessary
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Parametric Sketching