In my previous post I created a cone that has the same base radius as the cylinder and a top radius of zero. Since the purpose of this cone is to subtract material from the large cylinder, I need to modify the base radius so there will be a rim around the top of the cylinder after the cone is subtracted. Modifying a solid cone is just as easy as modifying a solid cylinder. I’d like that rim to be about 4 units so I’ll use the cone’s quadrant grips to reduce the radius by 4.

Next, I’ll widen the top radius from zero (a sharp point) to a value of 20. 

 
Notice the top of the cone is below the base because of the way I originally created it. AutoCAD doesn’t care where the top is in relation to the base. If you look at the properties for the cone you’ll see a Base Radius, a Top Radius, and a Height.

 
Even though AutoCAD doesn’t care if the Top Radius is really on top, there is a difference. If you change the height of the cone, the base maintains its position while the location of the “top” adjusts accordingly. For example, I want to ensure that I have 4 units of material left at the bottom of the cylinder after I subtract the cone. So, I’m going to change the height of the cylinder from 14 to 10 units.

Key concept:

• The base of a primitive object maintains its position when the height changes

In previous posts, I created two cylinders and a sphere for the air hockey paddle. Now I’ll create a solid cone, which I’ll use to remove material from the large cylinder. I could create the cone with the correct values right from the start. But, since I’m still in the conceptual design phase, I’m going to draw a cone by snapping to the existing cylinder and then I’ll modify my design.

The Cone tool (CONE command) is available in the solid primitives flyout of the Modeling panel (with the 3D Modeling workspace current).

The options for creating a cone are similar to creating a cylinder (and a circle). First, you specify the location and size of the base of the cone. You can use the default center/radius option or choose from 3Point, 2Point, TanTanRadius, and Elliptical. Just like with drawing a circle in 2D, the option you choose depends on what you’re trying to create, what existing objects you can snap to, and what you know.

I’ll use the default Center/Radius option and snap to the center and quadrant at the top of original cylinder. After specifying the base of the cone, the default option is to enter a value or pick a point to specify the height. However, there are additional options as well. A right-click menu (and the Command line) enable you to pick 2 points to determine the height, pick a point to specify the height and change the orientation at the same time, or enter a value for the top radius.

If you don’t enter a value for the top radius, it assumes a value of zero and creates the cone with a sharp point. Also, keep in mind that, like a cylinder, the base and top of a cone don’t necessarily mean that the base has to be on the bottom and the top has to be on the top. For now, I’ll create the cone using a default top radius of zero and I’ll snap to the center at the bottom of the cylinder to specify the height.

Key concept:

• Cone tool creates a 3D cone similar to creating a 2D circle

Last month I had the pleasure of interviewing David Byrnes, author AutoCAD for Dummies, while I was in Vancouver. David shared some great time-saving tips and tricks from his book. You can now view the first videos in this interview series on the AutoCAD Exchange.

Join me on Wednesday, June 17 for a free AutoCAD Webcast where you’ll learn how to increase your productivity with the powerful parametric drawing tools in AutoCAD 2010. This is an extra special session as David Byrnes, author of AutoCAD 2010 for Dummies, will join us with his thoughts on AutoCAD’s parametric drawing tools.  We will also be giving away free copies of AutoCAD 2010 for Dummies. Sign up now and don’t miss this opportunity!

Moving along the design process for the air hockey paddle, I’ll create a second cylinder within the original cylinder that I created in my previous post. Since I want the two cylinders to be concentric, I’ll use the center object snap. As you might imagine, a cylinder has two center object snap points- one at the base and one at the top. 

 
It doesn’t matter which one I choose because it’s easy enough to change later as my design evolves. For now, I’ll go ahead and pick the center osnap at the bottom of the existing cylinder. I’ll also pick rough points to define the radius and height for the new cylinder. I, of course, could enter exact values as well.

 
I’ll continue creating the air hockey paddle by drawing a sphere at the top of the cylinder. The Sphere tool (SPHERE command) is available in the solid primitives flyout of the Modeling panel (with the 3D Modeling workspace current). 

 
Drawing a sphere is much like drawing a circle. You can use the default center/radius option or choose from 3Point, 2Point, and TanTanRadius.

 
I’ll use the default center/radius option and place it at the center of the top of the cylinder then use the quadrant osnap to specify the same radius as the cylinder.

 
Even if you’re completely new to 3D design in AutoCAD, these tools should feel familiar based on your 2D experience.

Key concept:
• Sphere tool creates a 3D sphere similar to creating a 2D circle

Grip editing is one way to change the shape of a solid primitive object. Another way is to enter specific values for key properties. The properties vary depending on the type of solid primitive. For example, a solid box has properties for length, width, and height; whereas a cylinder has properties for radius and height. You can view and modify these properties in the Geometry panel of the Properties window. As you change the values, the geometry in the drawing editor updates.

Key concept:

• Enter values in the Properties window to modify the size and shape of a solid primitive

AutoCAD has had the ability to create solid primitive objects, like cylinders, all the way back to AutoCAD Release 12. However, until AutoCAD 2007, those objects were not easily editable. You practically had to know exactly what you wanted to draw before you started. That might work for creating as-built models but it made conceptual design challenging and time-consuming. Fortunately, AutoCAD 2007 took a huge leap towards true conceptual design. You can easily edit primitive objects using grips or the Properties window. For example, as I create the design for my air hockey paddle, I can experiment with the size and shape of the existing cylinder. Selecting a cylinder displays grips a move grip (square) at the center of its base. Picking that grip makes it easy for me to move the cylinder to another location (just as you would expect from your 2D experience).

Selecting one of the four quadrant grips enables you to edit the radius of the cylinder (again, just like you expect when editing a 2D circle).

Selecting stretch grip at the center of the base enables you to change the height and, at the same time, change the location of the base.

 
Selecting the grip at the other end of the cylinder enables you to edit the height of the cylinder without changing its base. 

Did you notice that I described that grip as being “at the other end” rather than being at the “top”? That’s because the base could just as easily be on top (or on the side or anywhere else). I could, for example, grip edit the “top” of this cylinder, and drag it below the base… now it’s the bottom.

The importance of distinguishing between the base of a solid primitive object and “the other end” will become more apparent in future posts.

Key concept:

• Grip edit to modify the size and shape of a solid cylinder

The Autodesk Simulation User Experience Team would appreciate your feedback on the relative importance of different types of energy analysis data during the early conceptual design phase of a project.  The survey should take less than ten minutes to complete.

Who Should Participate?
Architects, Designers, Energy Analysts, Mechanical Engineers focusing on HVAC, and those who are doing design work with a focus on sustainability. Please forward this survey to any colleagues in these roles who may be interested.

Survey link:
http://www.surveymonkey.com/s.aspx?sm=PPR_2fCiIHq_2fueXqmnVoyUlw_3d_3d

Survey will be active: June 1 – 8, 2009.
 
Thanks!
Autodesk Simulation User Experience Team

Now I’m ready to start designing the air hockey paddle. I’ll begin by drawing a solid cylinder. The solid cylinder tool is available in the Primitives panel on the Home tab of the 3D Modeling workspace. You’ll find a flyout with all the solid primitive tools. The box tool is displayed by default but the flyout will update to display whatever tool you used last. If you’re a keyboarder, you can use the command alias CYL (CYLINDER command).

Drawing a cylinder feels very much like drawing a circle. Compare the prompts. You can create a circle based on 3 points, 2 points, or 2 tangents and a radius in addition to the default option which requires you to specify the center and radius.

You can create a cylinder using the same options (3P, 2P, Ttr). In addition, the cylinder tool includes an Ellipse option that enables you to create an elliptical cylinder (similar to drawing an ellipse). For now, I’ll use the simple and familiar default option by specifying a center and radius for the cylinder.

If you know exactly where and what you want the cylinder to look like, you can pick exact points or enter specific values for the center and radius (just like drawing a circle). But, if you’re in the conceptual design phase and starting with a blank drawing, that may be more information than you know. Fortunately, it’s easy to modify the cylinder even after you create it. I’ll quickly (and sloppily) pick two points to specify the center and radius. It feels and looks just like a circle doesn’t it? Except now, because it’s a three dimensional cylinder instead of a two dimensional circle, it’s prompting for height. You can pick a point or enter a value.

From the top view, the height isn’t obvious. Even after I specify a height, it just looks like a circle. When you work in 3D, you’ll want to view your model from different angles, not just from the top as we’re used to in 2D design. 3D viewing and navigation is an entire topic on its own but you don’t have to learn everything there is to know about it in order to get started with 3D modeling. I’ll point out key tools along the way. For example, one of my favorite viewing tools is Orbit. You can orbit the model by pressing the Shift key and middle mouse button and moving the mouse. The orbit symbol appears at the cursor and you can easily and intuitively adjust your view of the model.

Key concepts:

• Cylinder tool (CYL command alias) creates a 3D cylinder similar to creating a 2D circle with height
• Shift key and middle mouse button enable you to orbit the model