Computer Aided Design (CAD)

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Computer Aided Design (CAD)

• Prof. Paul Kurowski
• Oct. 28, 2009

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Evolution of CAD Technology
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Manual drafting Since 1970s electronic drafting
board
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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

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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

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Early 1980s wire frame geometry
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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

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What is this?
Problems with wire frame models
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Late 1980s Surface Modeling
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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

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A Surface Model created using Alias StudioTools
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Surface Model created using Rhino
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Since early 1990s solid geometry
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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

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MODERN CAE TOOLS
COMPUTATIONAL FLUID DYNAMICS
FINITE ELEMENT ANALYSIS
CAD SOLID, PARAMETRIC, FEATURE BASED
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MOTION ANALYSIS
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CAD (Computer Aided Design) is at the hub of
other CAE (Computer Aided Engineering) tools
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Parametric, Feature-based Solid Model
PARAMETER
SOLID GEOMETRY
BASE FEATURE (POSITIVE SOLID)
CHILD OF BASE FEATURE (NEGATIVE SOLID)
panel 01.SLDPRT
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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

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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.

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Feature-based Modeling Process

• Create base part
• Add features until final shape is achieved

Extruded Base
Extruded Cut
Extruded Cut
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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

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Solid Edge
Feature Pathfinder
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Pro/E Wildfire
Model Tree
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SolidWorks
Feature Manager Design Tree
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Modifying Parts

• The part is created from the history tree
• Features can be added, deleted and re-ordered
• Feature parameters can be changed

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ES1050 part 01.SLDPRT
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ES1050 part 01.SLDPRT
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ES1050 part 01.SLDPRT
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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

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In ES1050 we use SolidWorks CAD You can burn
your installation CDs in SEB1005 Installation
instructions are here http//www.eng.uwo.ca/desi
gncentre/CAD20resources/default.htm
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DESIGN CENTRE WEB SITE
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DESIGN CENTRE WEB SITE - CAD RESOURCES
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CAD RESOURCES SolidWorks TUTORIALS
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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
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