Topic: Problem with revolved surfaces imported from IGES and others

Technote 106
Date: 11/95
Product: Advanced Milling, FreeForm Machining
Version: Up to v11.5

Problem:
Information on creating surfaces, in the CAD appliation, in a way to ensure a better IGES import.

See Technote 82 for other tips.

Spheres and other surfaces with poles:

We sometimes see badly created surfaces when surfaces with poles are translated into FFM. Examples of these surfaces are: a sphere which has poles (i.e., the earth's north and south poles), the apex point of a cone, or any curve that is rotated about its endpoint to create a surface. The problem is usually seen when a trimmed area includes the pole or the pole is at a trimming curve vertex. You can try the following options to resolve this problem.

• Rotate the base sphere surface so the pole is off the curve and/or outside the trimmed area.
• Punch a tiny hole (e.g., a 0.002 inch diameter hole) in the surface at the pole.

If pre-processing the model in the CAD system does not help, you can fix up the surface in FreeForm Machining.

Replace the badly trimmed surface by using the Coons Surface modeling tool. You can use the Extract and Generate Mesh modeling tools to get curves from the original surface with which to rebuild it.