Transcript CAD 2011 - Western Engineering

ES050 – Introductory Engineering
Design and Innovation Studio
Computer Aided Design
(CAD) Part 1
Prof. Paul Kurowski
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Evolution of CAD Technology
Solid
model
Surface
model
Wire frame
model
Drawing
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Manual Drafting
Manual drafting
Since 1970’s: 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, errorprone, 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, there is no 3D
representation of the object
Example: AutoCAD
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3D Wire frame Modeling
Early 1980’s: 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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3D Wire frame Modeling
?
?
Problems with wire frame models: What is this?
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3D Surface Modeling
Late 1980’s: 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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3D Solid Modeling
Since early 1990’s: solid geometry
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3D Solid Modeling
Not parametric
Parametric
Not feature based
Feature based
This has become the
industry standard
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3D 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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There are many 3D solid, parametric,
feature based CAD systems
They all work basically the same way
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At the Western Engineering we
have selected SolidWorks
Double-click this icon on your desktop
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First look at SolidWorks
Click this icon and open
file bracket.sldprt
Opening a part
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First look at SolidWorks
Feature
Manager
window
This is model view window
You should now see this, notice two windows.
Model opens in isometric view
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First look at SolidWorks
Click this icon to
open pop-up
window with
different views, try
selecting them as
you like.
Lets’ find out how to see the model in different views
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First look at SolidWorks
You can place the model in any position by
moving the mouse.
Press middle mouse button to rotate the model
Press middle mouse button and Ctrl key to pan
the model
Press middle mouse button and Shift key to
zoom in and out the model
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First look at SolidWorks
At any time you may Zoom to Fit the model
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First look at SolidWorks
Now that we know ho to open the part and how to
manipulate views, let’s find out what does is mean that our
CAD system is feature based.
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Features
Here is the Feature Manager window. Notice three features: Base-Extrude, Cut-Extrude and Fillet1.
They are listed in chronological order: Base-Extrude was created first, Fillet1 was created last.
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Model Roll-back
Roll-back bar
We’ll now retrace the process of model creation. Move the cursor over the Roll-back bar until a little
hand shows up, then move the hand up.
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Model Roll-back
Roll-back bar
With the Roll-back bar positioned above the Fillet1, the fillet disappears from the model.
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Model Roll-back
Roll-back bar
With the Roll-back bar positioned above the Cut-Extrude1, the hole and the fillet disappear from the
model.
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Model Roll-back
Roll-back bar
With the Roll-back bar positioned above the Base-Extrude the entire model disappears.
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Features
It is now clear that our model consists of three features created in the specific order. In our model
these features can’t be reordered. In other cases some features may be re-ordered.
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Now let’s find out what does is mean that our
CAD system is solid.
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Section view
Move the roll-back bar all the all the way down, place the model in isometric view and select the
Section View. You’ll see that material occupies the entire volume.
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Mass Properties
Mass properties
icon
Evaluate tab
Mass properties assigned:
1060 Alloy
Here is another proof that SolidWorks is a solid C AD system. Select the Evaluate tab and then
Mass Properties icon
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Mass Properties
Action from the previous slide displays Mass Properties Window listing volume, mass and mass
moments of inertia of the model.
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Summary
In this lesson we have:
Learned a brief history of CAD
Introduced SolidWorks CAD system
Explained what does it mean that a SolidWorks is solid
and feature based.
In the next lesson we’ll find out why exactly this is a
parametric system. This will require us to build a modify a
CAD model
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