AutoCAD Insider: AutoCAD 3D Conceptual Design 124

In my previous post, I created a solid box that aligned with opposing quadrants of a solid cylinder. A close (very close) look at the ends of the box shows the corners of the box hanging over the edge of the cylinder. That may cause production problems (oops!) when we try to insert the bottom plate into the air hockey paddle. Plus, it gives me the perfect opportunity to show you the Interfere tool.

First we’ll move the cylinder and box objects into position within the air hockey paddle. Viewing the model from below, I’ll use the MOVE command. I’ll select the center of the bottom of the cylinder as the base point and the center of the bottom rim of the air hockey paddle as the second point (the inner and outer edges of the rim are concentric so it doesn’t matter which one I pick).

If, when specifying the base point, I had picked the top center of the cylinder instead of the bottom, the cylinder would not be flush with the bottom rim of the air hockey paddle.

The interference of the box with the main air hockey paddle is tough to see because it’s so small. Hopefully, your experience and intuition tell you there’s interference. Or, just trust me.

To prove it, we’ll use the Interfere tool, which is located in the Solid Editing Panel of the Home tab.

The Interfere tool is one of the few AutoCAD commands (like Subtract) that require two selection sets. As far as I know, the order of the selection sets doesn’t matter.

To check for interferences between the air hockey paddle and the cylinder and box objects, I’ll select the air hockey paddle as the first selection set (pressing enter to end the selection set). Then I’ll select the box and cylinder as the second selection set. I’m confident that the cylinder doesn’t interfere with the paddle but it doesn’t hurt to check anyway. After completing the second selection set, AutoCAD displays the Interference Checking dialog box and creates temporary solid objects (in red) where any interferences occur. The dialog box offers various tools that enable you to examine the interferences while they’re temporarily displayed.

When you close the dialog box, the red interference objects are automatically removed. I usually prefer to maintain those objects in the drawing because I can then use them to remove the excess (interfering) material from my model. To do this, you want to turn off the option in the dialog box to “Delete interference objects created on Close”. After closing the dialog box, a new solid is included in the model. Even though these particular interferences are not adjacent, they’re created as a single solid. The interferences are just slivers in this case but, none-the-less, I want to remove that extra material from the box. What tool should I use?

The Subtract tool of course! Using the subtract tool, I’ll first select the box and then (after ending that selection set), I’ll select the interference solid. The change is barely noticeable but I’m sure happy we discovered the problem during the design phase and not after we began production!