"UG doesn't allow you to delete geometres in sketcher which is used by a extrusion."
That might have been true up through NX 2, but starting in NX 3 you can delete sketch curves even if they are used as part of an extrusion profile. Granted, the resulting model may not be what you expect, but it will let you do it and it will at least try to perform an update.
John R. Baker, P.E.
Product 'Evangelist'
NX Product Line
UGS Corp
Cypress, CA
Speaking of sketcher, one feature I really miss from Pro/E is the ability to 'replace' one sketch entity with another. This can avoid downstream feature failures that you might otherwise get by just deleting a sketch entity and redrawing it.
For example, in Pro I could replace a line segment with an arc segment and all the downstream geometry that referenced the line would now reference the arc.
Any chance that this functionality is present in NX5?
Add blends around the 'top' of the block (if you want to make this bulletproof, use the 'Selection Intent' option of 'Face Edges' when blending the 'top' of the block).
If you're running NX 3, blank the solid and then edit the Sketch. If you're running NX 4, just edit the Sketch 'with rollback'.
While in the sketch editor, add a 3 point arc selecting the end points of one side of the rectangle.
Now delete the side of the rectangle that the arc 'replaced'.
Now leave the sketch task.
If you blanked the solid, unblank it.
Now look at your results. Was this what you expected?
BTW, you can actually do this with NX 2 as well, just that it takes a couple of extra steps, but it does work.
John R. Baker, P.E.
Product 'Evangelist'
NX Product Line
UGS Corp
Cypress, CA