using 3d autocad® surfaces to create composite solids · 1 using 3d autocad® surfaces to create...
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Using 3D AutoCAD® Surfaces to Create
Composite Solids J.D. Mather – Pennsylvania College of Technology
GD211-2P This class explores the creation of 3D surfaces used in creating composite solids. Many
solid shapes can only be created by editing with surfaces. AutoCAD now includes powerful tools for
creating surfaces and using them in creating or editing solids. Examples appropriate for mechanical,
architectural, and civil engineering will be demonstrated.
About the Speaker:
Dr. Mather is an assistant professor of CAD and Product Design at Pennsylvania College of Technology
affiliate of Penn State University. He has taught AutoCAD courses for 13 years and has been an
Autodesk Inventor Certified Expert since release 7. His advanced 3D Modeling tutorials are studied by
users around the world.
http://home.pct.edu/~jmather/content/CAD238/AutoCAD_2007_Tutorials.htm
Previously he worked in industry for 15 years, including positions as Journeyman Machinist, Research &
Development Technician and Industrial Engineering Technician.
http://home.pct.edu/~jmather/AU2007/GD211-2P%20Mather.pdf
http://home.pct.edu/~jmather/AU2007/GD211-2P%20Dataset.zip
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Using 3D AutoCAD® Surfaces to Create Composite Solids
Session Objectives
Learn how to create and use planar surfaces for creating or editing solids.
Learn how to create Extruded, Revolved, Swept and Lofted surfaces for use in creating or editing solids.
Use surfaces with the Thicken Surface command to generate solids.
Use the Slice command as a more efficient method of creating fairly simple geometry.
Learn to use hybrid surface/solid modeling using the Slice command to create complex geometry.
Target Audience
Anyone who has used surfaces in earlier releases of AutoCAD and would like to
learn the new AutoCAD surfaces techniques, or who has particularly complex
geometry they need to create.
Introduction
AutoCAD now provides powerful surfacing tools to create complex composite solids. At one
time we were limited to prismatic geometric shapes like boxes, or cylinders and spheres and
whatever clever techniques we could devise to combine these primitive geometries to create
more complex geometry.
Often a solid geometry was not possible and we had to limit our design to surfaces. Surfaces
were difficult to edit and did not return valuable information such as volumetric data.
We can now use composite techniques using both surfaces and solids to generate complex
algorithmic or rules-based solid geometry.
There is no longer a need for a separate tool set for surfaces – we use the same tools for
surfaces or solids.
The 3D “virtual model” is a source of validation of the information to build the real world.
The Lesson
The real world isn’t flat.
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Prior Knowledge Expectations
For this class I will assume that you have attended the:
GD105-1P 3D AutoCAD® for All of Us
GD111-3P 3D Visualization and Solid Primitive Design
GD115-4P Using AutoCAD® for Sophisticated Solid Model Design
GD201-2P Editing 3D AutoCAD® Solids
classes…
or
…have some prior experience with the Dashboard in the 3D Modeling Workspace.
Layers control panel
3D Make control panel
Visual Style control panel
Light control panel
Materials control panel
Render control panel
3D Navigate control panel
2D Draw control panel
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Getting Started
We may use other tools in the 3D Make control panel but I am going to concentrate on the
following tools:
We will look at the surface creation/editing functionality of these tools.
Extrude Slice
Revolve Thicken
Sweep Convert to Solid
Loft Convert to Surface
Planar Surface
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Solids vs
Surfaces
(Or maybe I should say Solids &
Surfaces.)
If we exploded a cube we would
find that it is made up of 6
Surfaces. If we exploded it
again we would find that the
surfaces have a total of 24
edges.
Whenever we have surfaces that meet in
unambiguous “watertight” edges we can
create our geometry such that the edges
are combined and shared. The result is a
solid that represents a volume and can
easily be edited.
We refer to the Faces of the solid rather
than surfaces.
In our cube example we have 6 faces
with 12 edges.
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Extrude
If you run the List command on
the entities you will see that the
black entity is a polyline, the
red entity is a line, the green
entity is an arc and the cyan
entity is a spline. Although the
shape forms a closed area it is
not a closed polyline, boundary or region.
If we Extrude the entities we find
that the result is 4 independent
and infinitely thin surfaces
The old Surfaces toolbar is no longer listed. We could type in the old commands, like rulesurf,
but the surfaces created using the standard 3D Make tools with an open profile are much
easier to create and more powerful as well.
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Revolve
Again, with an open profile the
resulting feature when using the
Revolve tool will be a surface.
The Revolve surface
can be any angle up
to 360deg.
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Sweep
We have a variety of Sweep paths represented by lines, polylines, 2D splines and 3D splines.
Tip: If the Sweep fails try changing the UCS. Although the command should re-align the
profile I have had instances where changing the UCS will complete a swept feature that
otherwise fails.
Try with Twist 180 deg along the magenta line.
Try with Scale
Try with Alignment Yes/No.
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Loft
Like all of the surface features,
Loft of surfaces works
essentially the same as loft of
solids. There is no longer a
need for a separate set of
surface tools.
Create our open-profile cross-
sections and guides or a path
as needed and we are ready
to Loft surfaces.
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Planar Surface
For a Planar
Surface all we
need is a closed
area. Notice that it
isn’t necessary to
have a closed
polyline, boundary
or region.
We can select Objects to define the Planar Surface edges or if it is rectangular surface simply
click two points on the screen.
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Slice
This example is meant to be a simplified representation for calculating the volume of earth to be
removed from a mountainous terrain to get to a volume of coal.
Tip: I have had trouble in r2008 with the wrong side sometimes being retained. Simply undo
and Slice again, this time electing to keep both sides. Then delete the side you don’t want.
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Thicken
We can create a solid using any surface with the Thicken command. The surface can be
thickened to either side by changing the +/- value.
The only concern we have is the resulting solid cannot self-intersect.
Consider for example offsetting an arc. We cannot offset the arc
beyond its centerpoint. The self-intersection problem arises most often with Lofted surfaces
and might not be readily apparent where the intersection would occur.
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Using Surfaces – Example 1
Here is an example utilizing Thicken, Taper Faces, Fillet, Shell and Presspull.
Here’s a tip on Shell worth the
expense of attending AU – Shell in
2D wireframe for faster results rather
than while shaded. And have only
one modelspace viewport rather than
several tiled viewports.
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Using Surfaces – Example 2
The Slice command can be
used in conjunction with
surfaces to edit solids.
We can very quickly create
Planar Surfaces for Slice
by allowing the DUCS to set
our UCS on appropriate faces.
Notice that each member is highlighted as you are prompted to select which side to retain or
keep Both sides.
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Using Surfaces – Example 3
Using the new AutoCAD tools we’ve learned let’s simplify the design process of our hand tools.
As you watch think about, “How can these
techniques be used in your work?”
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Using Surfaces – Example 4
And for a little fun let’s model a toy car body.
All we need is a simple wireframe.
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And a few surfaces.
The real word is not flat.
By using a combination of the AutoCAD solid modeling and surface tools we can generate
composite designs.
Have you recognized any ways you use these techniques in your work?
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You might want to Rapid Prototype your parts. Use the STLOUT command to generate a stl
file. With a physical rapid prototype model you can verify much of your design before sending
the design to the manufacturing floor.
Tip: Facetres variable controls the stl resolution.
Tip: Your model must be in the positive xyz octant when using the stlout command you will get
an error.
If you run into a problem with your application of the techniques demonstrated in this class
simply send me an email