## 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

### Topics

3D primitives and model types

Constructive Solid Geometric Modeling

## 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

## Solid Model Boolean Operations

Constructive solid geometric modeling (CSG) uses Boolean operations and constructive operations to create a solid model.

### Boolean operations

• Difference (Cut, Subtract): -
• Intersection: ∩

In order for Boolean operations to be logical, the features must be either overlapping or touching.

## 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

## 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 3-5, all names on one paper

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