Blend Restrictions in Practical Use

If the user wishes to blend a sequence of edges that cross several different faces, such as the intersection formed when a thruster tube intersects several patches, then the user should concatenate the group of patches together, using either the tangent or curvature option, before intersecting the thruster tube, as the blended edge must be continuous. Using the JOIN command to stitch the patches together does not produce a continuous edge from the intersection, therefore the blend will not work.

This is a limitation with ACIS and is to be improved in the future.