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 2D features then use a 3D construction operation, such as extrude, revolve, or sweep, to create a 3D model.
Trang 1Parametric Sketching
Trang 2Solid primitives not typically supported in parametric modelers must create a 2D profile, then sweep
Trang 3Feature Creation Procedure
1. Choose sketch plane, either a:
Default work plane
Planar face of existing feature
Work plane
2. Rough sketch
Some geometric constraints applied
3. Add/delete geometric constraints
4. Parametric dimensioning
5. Feature creation
6. Repeat 1 - 5
Trang 4Construction 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
Trang 5Default Construction Geometry:
Inventor
Work planes – mutually perpendicular
YZ
XZ
XY
Work Axes
X (red)
Y (green)
Z (blue)
Work Point
Origin of WCS
Trang 6Rough Sketch
Parametric sketching imitates actual
sketching process rough, approximate
Trang 7Sketch Plane Views
View normal to
sketch plane Isometric View
Trang 8Geometric Constraints
Typical constraints include: vertical,
horizontal, collinear, concentric, tangent, etc Inventor constraints
Trang 9Display Geometric Constraints
Software includes option to show
constraints
Trang 10Add/Delete Constraints
User can manually (explicitly) add constraints
equal tangent concentric
Trang 11Parametric Dimensions
Add parametric
dimensions to fully
constrain profile
Each parametric
dimension has two
components:
Numerical value
Name
Fully Constrained Sketch
Trang 12Parametric Dimensions - 2
Default parameter names (e.g., d0) can be changed Equations can be used to generate parameter value
Trang 13Under and Over-constrained Sketches
Under-constrained Over-constrained
Vertical position of
hole not specified
Angle not necessary
Trang 14Parametric Sketching