1. Extruding Solids with AutoCAD
Lecture 15
Instructor:
This lecture is particularly directed at Solid Modeling with AutoCAD 2002 but the principles are the same for other CAD programs.
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2. Topics for Today QUIZ on Sections
Alternative Methods for Solid Modeling
Extrude a Region
Revolve a Region
Instructor:
In the previous exercises, the students used Constructive Solid Geometry (CSG) to create solids. Today the focus will be on extrusion and revolution to create solids.
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3. How would you model this using primitives??? It would be complicated!
Today’s Project
How would you model this using primitives???
It would be complicated!
Instructor:
Have the students figure out how many boolean operations it would take to create this object.
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4. Could it be modeled as a solid using only primitives?
Solid Model of Roller
What about this part???
Could it be modeled as a solid using only primitives?
It would also be very complicated!
Instructor:
This could be done with primatives. Again, ask the students how they might do this with Boolean operations and the chamfer and fillet functions.
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5. We Need New Methods of Modeling!
Extrude a Region
Create a 2D profile and extrude it along a path to create a solid.
Can be used for almost any shape
Revolve a Region
Create a 2D profile and revolve it about an axis to create a solid.
Used for modeling parts that are symmetric about a center axis
Parts can be modeled using both methods and Boolean commands
Instructor:
Here are the basic steps for doing extrusion and revolution. Note that these can be combined with Boolean operations.
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6. Extruding A Region
Create a 2D “profile” of the part’s external geometry
Extrude this profile through the depth of the part
Using the coordinate system options, create other solids for the holes, cut-outs, or tabs.
Use the Boolean Commands to subtract, etc.
Instructor:
The profile can be drawn in any viewport and typically is extruded in that viewport along an axis perpendicular to the profile.
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7. Notes on Extruding 2D Profiles
This is a very powerful tool – any closed string of lines can be made into a solid model
It is IMPORTANT that the string of lines be closed!
The part will always be extruded perpendicular to the 2D profile.
Some thought is required about the steps – what to use as the base geometry, what to add/subtract using Boolean commands.
Instructor:
Emphasize bullet 2 on this slide.
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8. Revolving A Region
Create a 2D ‘profile’ of one side of the part’s central axis
Rotate this profile around the central axis of the part
Either draw a center line or know the coordinates of this axis
Profile can be rotated 360° or some other angle
Create holes, cut-outs, or tabs as needed
Instructor:
Please call bullet 2 first subheading to the students attention. Establishing the axis first is critical to revolution.
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9. Re-examine the Parts
Instructor:
The students will be doing these exercises with the aid of the AutoCAD (or other CAD) tutorial book. In the case of the wheel, if the profile is drawn correctly, it only takes one more step, a revolution of 360 degrees to produce the solid. The cut block is considerably more complicated even with extrusion.
Using these techniques, modeling these parts as solids would require much less steps then modeling using only solid primitives
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10. Assignments Dwg 29 – AC3D Lesson 7 – V-Block
Create model as outlined in the lesson
Create a layout showing the part in the SE Isometric View (use World UCS)
Dwg 30 – AC3D Lesson 7, Exercise 4
Create the using Extrude Command
Instructor:
Keep emphasizing to the students that they need to be able to work through the tutorial and then do an exercise in addition. It is doing the second object with the methods in Lesson 7 that cements the knowledge about how to use the system. They will be expected to use AutoCAD without the tutorial on the test.
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