Using Surfaces with Projected Curves
by Adrian Fanjoy, Technical Services Manager, CATI
 

In this article I would like to show a method of creating some seemingly simple geometry that in actuality is rather complex.  I am going to show a method of modeling this fan cover, specifically the bracket features that are used to mount the cover to the fan’s casing.

As you can probably imagine my first suggestion is to model only half of the part.  So I only have to create one of the bracket features.

The rings that are the actual cover are simple revolved features so we are not going to explore our options with those in this article.  

As you can see the bracket can actually be described in two views.  

For this method of modeling our part I am going to use a surface feature to describe the profile of the bracket feature.  This will be a revolved feature due to the nature of the part as a whole.

The Sketch for the feature will look similar to this:

The feature itself will look like this:

Remember we are only revolving 180deg because we are going to mirror the part eventually.

A plane must be offset out from the surface parallel to its two main faces.  This is going to be the sketching plane for the next sketch.  In this case Plane4 has been offset off of Plane1.

The sketch will describe the centerline of the bracket from the top view.

Remember that your sketch cannot extend beyond the outside edge of the surface.  If it does the project curve command will fail.

The next feature is a projected curve:

By selecting the sketch created from the top view in the previous step and selecting all of the faces of the revolved surface created earlier the result is a three dimensional curve that satisfies the requirements from both directions.

This curve will be the centerline of the wire bracket.

The final step is to create the actual solid geometry.  To do this we will create a sweep that follows the path described by the projected curve.

We will need a sketched profile that is perpendicular to the path of the curve.  This is created by dropping a reference plane normal to a curve using the curve as the reference edge and the end point of the curve as the point.

Next you must create a sketch on the new plane of a circle and make the center point of that circle coincident to the projected curve.

This sketch will be the profile that is swept about the projected curve to create the solid geometry of the wire bracket.

Don’t forget to hide the surface feature to allow the model to be viewed without interference.

The use of Projected curves can be very powerful but even more powerful and flexible when used in conjunction with surface geometry.