SOLIDWORKS Extend Surface command does not work with my model?

You are a tool and die designer and your customer has just sent you an IGES file containing a solid with a complex face which has to be used as reference for your embossing die. In order to create your punch and die inserts, you need to isolate that surface and extend it. If you can do that, you will take the job, if not – you have to refuse it.

You have no problem offsetting that face in order to create the surface body, but when you try to apply the Extend Surface command to the new surface, an error message pops up…

You are right, the Extend Surface command does not work in this case. Fortunately, there is another command available in the Surface toolbar – Untrim Surface.

With Untrim Surface, you can patch surface holes and external edges by extending an existing surface along its natural boundaries. You can also extend the natural boundaries of the surface by a given percentage, or connect the end points to fill the surface. Untrim Surface tool can be used with any imported surface or surfaces that you create.