ENG 004 Lecture 8, Oct 23, 2012
Announcements
 Homework #3 due now
 Homework #4 will be posted after class
 Midterm coming up on Thursday, November 1
 Read Chapter 4
Topics
3D primitives and model types
Constructive Solid Geometric Modeling
3D Primitives
3D Primitives
3D Primitives
3D Primitives
3D Primitives
Ruled Surfaces
Undeveloped Surface
3D Modeling: Node Model
3D Modeling: Surface Model
3D Modeling: Solid Model
Sketch Planes

World coordinate planes (WCP) are associated with the world coordinate
system (WCS)
Sketch (Work) Plane
Coincident or relative to a WCP
Can be a plane or projected plane that already is in the model

Sketch Plane Creation
Solid Model Boolean Operations
Constructive solid geometric modeling (CSG) uses Boolean operations and
constructive operations to create a solid model.
Boolean operations
 Join (Union, Add): ∪
 Difference (Cut, Subtract): 
 Intersection: ∩
In order for Boolean operations to be logical, the features must be either
overlapping or touching.
Boolean Operations: Union
Boolean Operations: Intersection
Boolean Operations: Difference
Boolean Operations: Difference
Solid Model Constructive Operations

 Define a work plane
 Define a closed profile (sketch) using 2D primitives
 Infinite, unbounded 2D plane placed and oriented anywhere in the
3D domain of the model
 A local coordinate system (LCS) or user coordinate system (UCS)
is associated with the World Coordinate System (WCS)
 A 2D profile is defined

Extrusion
Revolution
Revolution
Sweep
Loft
Constructive Operations
Extrude (linear sweep)
Define length and direction of the extrusion. The direction cannot be
parallel to the work plane.
Revolve
Define the axis and amount of rotation
Sweep (path based sweep)
Define a space curve along which the sweep occurs
Loft
Define a space curve and intermediate profiles along the curve.
Feature Planning
 History tree
 Logical sequence of procedures used to create a solid model
 There is no unique history tree for a particular part being
modeled
Sketch Constraint Quiz
pg 117 for constraint types, groups of 35, all names on one paper
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