I fired up V15 and created the file attached, one created with sweep, one with revolve, as I'd suggested earlier. It's interesting to note how far TC's come. I could get away with a lot more in later versions than in V15, V15 peppered this exercise with selfintersection warnings, and limited the revolved example to no lower a figure than .21whatever-of-a-coil, presumably for some variation of that. With sweep, an open profile for the ramp was much more tolerant than closed, I assume because a closed profile will produce a selfintersecting solid. I remember making the decision to upgrade from V15 to V17 because V17 introduced more sophisticated beziers, but I think it's easy to overlook the other improvements that've happened in less obvious areas. (Maybe, just maybe, I'm better than I used to be, too
). Aside from this, which I assume is ACIS kernel behavior, the other thing that struck me is how limited the inspector bar is compared to later versions. No deltas, no position, no size. Kudos IMSI. Still don't like the dark colour scheme, though. I'm older, my eyesight's worse, my PC's are smaller. Dark is detrimental, not an improvement.