Monday, December 19, 2011

3D AutoCAD – work sequence to eliminate overlapping volumes

There is more than one way to accomplish the above stated goal.  I'm going to focus on using the interfere command.  Let's just draw a few overlapping solids.  You can use any overlapping solids if you want to follow along.  Here I've just created some boxes that overlap:

We don't really like intersecting solids very much - not if we're modelling something real.  Real solid objects don't like to coincide with each other very much and so we want to eliminate the intersections.  If we only want a single piece out of the above, we would use the union command.

But, let's suppose we want to model three different pieces - perhaps because we intend to manufacture and assemble the pieces afterwards.  In that case, we want to remove the offending intersections from one or more of our shapes.  Ideally, we don't want to have to create all such intersections ourselves and then subtract them from the appropriate shapes.  Enter the interfere command:

  1. Create and make current a new layer called, say, interfere and use a distinct colour for it.
  2. Command line: interfere
  3. Select all relevant objects - those which may have intersections you wish to remove.
  4. <enter> or <space>
  5. <enter> or <space> to implement the default <checK> command
  6. Now you'll see:

7.  Uncheck the box that says delete interference objects on Close, and then Close the dialog box.
8.  Turn on selection cycling (the right-most option at the bottom where all of the modes are).
9.  Use the subtract command.
10.  Select the object you want to subtract from and press <enter> or <space>.
11.  Using selection cycling, select relevant the object(s) created from the interfere command:

 After subtracting all of the relevant shapes (2 in my case) it looks like this:

Here I've moved it around a bit to show the results more clearly:

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