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Computer Aided Design (CAD). Prof. Paul Kurowski Oct. 28, 2009. Solid model. Surface model. Wire frame model. Drawing. Evolution of CAD Technology. Manual drafting Since 1970’s: electronic drafting board. 2D representations used to represent 3D objects multi-view drawings pictorials

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computer aided design cad

Computer Aided Design (CAD)

Prof. Paul Kurowski

Oct. 28, 2009

evolution of cad technology

Solid

model

Surface

model

Wire frame

model

Drawing

Evolution of CAD Technology
slide3

Manual drafting

Since 1970’s: electronic drafting board

manual drafting
2D representations used to represent 3D objects

multi-view drawings

pictorials

Standards and conventions developed so that 3D object could be built from drawings

Drawings created manually or using 2D CAD

Difficult to visualize, error-prone, time-consuming

Manual Drafting
2d cad
Simply replaces manual drawing

Provides a set of drawing tools to create 2D elements

Lines, circles, arcs, etc.

More accurate, easier changes to drawings

Still no 3D representation of the object

Example: AutoCAD

2D CAD
3d wire frame modeling
3D Wire frame Modeling
  • Geometric entities are lines and curves in 3D
  • Volume or surfaces of object not defined
  • Easy to store and display
  • Hard to interpret - ambiguous
what is this
What is this?

Problems with wire frame models

3d surface modeling
3D Surface Modeling
  • Models 2D surfaces in 3D space
  • All points on surface are defined
    • useful for machining, visualization, etc.
  • Surfaces have no thickness, objects have no volume or solid properties
  • Surfaces may be open
solid parametric feature based modeling
Solid, parametric, feature based modeling
  • Complete and unambiguous
  • Solid - models have volume, and mass properties
  • Feature based -geometry built up by adding and subtracting features
  • Parametric - geometry can be modified by changing dimensions
slide15

MODERN CAE TOOLS

COMPUTATIONAL FLUID DYNAMICS

FINITE ELEMENT ANALYSIS

CAD

SOLID, PARAMETRIC, FEATURE BASED

…..

MOTION ANALYSIS

…..

CAD (Computer Aided Design) is at the hub of other CAE (Computer Aided Engineering) tools

parametric feature based solid model
Parametric, Feature-based Solid Model

PARAMETER

SOLID GEOMETRY

BASE FEATURE

(“POSITIVE” SOLID)

CHILD OF BASE FEATURE

(“NEGATIVE” SOLID)

panel 01.SLDPRT

solid parametric feature based modeling software
Solid, parametric, feature-based Modeling Software
  • High-end (more powerful)
    • NX (UGS)
    • Catia (Dassault Systémes)
    • Pro/Engineer (Parametric Technologies Corp.)
  • Mid-Range (easier to use)
    • Solid Edge (UGS)
    • Inventor (Autodesk)
    • SolidWorks (SolidWorks Corp.)

They all work basically the same way

feature based solid modeling
Feature-Based Solid Modeling
  • Parts modeled by adding features to a base part
  • Features represent “operations”
    • holes, ribs, fillets, chamfers, slots, pockets, etc.
  • Material can be added or subtracted
  • Features can be created by extrusion, sweeping, revolving, etc.
feature based modeling process
Feature-based Modeling Process
  • Create base part
  • Add features until final shape is achieved

Extruded Base

Extruded Cut

Extruded Cut

feature history trees
Feature History Trees
  • Most feature-based modelers show the features and their order in a graphical tree view
  • This view has different names, depending on the software
slide21

Solid Edge

Feature Pathfinder

slide22

Pro/E Wildfire

Model Tree

slide23

SolidWorks

Feature Manager Design Tree

modifying parts
Modifying Parts
  • The part is created from the history tree
  • Features can be added, deleted and re-ordered
  • Feature parameters can be changed
summary
Summary
  • Most CAD systems use solid, parametric, feature-based modeling
  • Parts are modeled by adding features to a base feature
  • Features can be easily added, deleted and modified
slide29

In ES1050 we use SolidWorks CAD

You can burn your installation CDs in SEB1005

Installation instructions are here:

http://www.eng.uwo.ca/designcentre/CAD%20resources/default.htm

slide33

Select the INCORRECT statement about solid, parametric feature driven CAD

A Geometry fully represent 3D object

B Base feature is created first

C Features can be deleted or modified

D It is a ‘hub” for CAE applications

E It is based on surface geometry