1. Creating a moveable set of mounting holes for a component
in a parametric 3D modeling program
©2013 Andrew Buc
This document grows out of a situation I’ve encountered on the job. An electronic
component would be mounted to a sheet metal bracket, and I would want to move the component
to a different location on the bracket. Of course, the same situation could arise with a mechanical
component. Screen shots are taken from SolidWorks, but the same principles would apply in
Autodesk Inventor (with which I’m also familiar) or another solid modeling program.
Create a sketch on the face the component will be mounted to. Using construction lines,
draw a geometric figure. The mounting holes will be at the corners of the figure.
3D modeling programs often default to drawing horizontal or vertical lines, but in this
case, you don’t want this. Draw the desired figure, with what would normally be horizontal or
vertical lines at some random angle to the horizontal or vertical. If the figure is a rectangle, then
you will still want parallel and perpendicular relationships between its sides. To make things
more interesting, we’ll assume that the mounting holes for the component form a trapezoid.
Notice the line between the midpoints of the unequal sides of the trapezoid. The point at
the midpoint of this line is at the center of the trapezoid and will be used to locate the hole
pattern relative to the edges of the bracket. The circles at the corners of the trapezoid will be used
to extrude the mounting holes.
Andrew Buc: 3DCADguy@andrewbuc.com Twitter: @3DCADguy
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2. Apply dimensions as desired to orient and locate the hole pattern: The zero-degree
angular dimension is struck between the central construction line and the edge of the bracket.
Extrude the holes from the sketch:
Andrew Buc: 3DCADguy@andrewbuc.com Twitter: @3DCADguy
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3. In the assembly, mate (in Inventor, constrain) the electronic component to the mounting
bracket. If the hole patterns in the bracket and the component are identical (and they should be),
then it will be enough to apply appropriate mates to 2 holes in the bracket and 2 corresponding
holes in the component:
Now, imagine that the electrical designer wants to move the component and rotate it 90
degrees. Change the dimensions in the sketch accordingly:
Andrew Buc: 3DCADguy@andrewbuc.com Twitter: @3DCADguy
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4. Close the sketch and rebuild the bracket and the assembly. Voilà!
Andrew Buc: 3DCADguy@andrewbuc.com Twitter: @3DCADguy
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