i have create this shape from curves (with command network).why the command shell dont work in this shape???
is my way wrong???

Hi billis - in this case your surface has an area where it is collapsed down and sort of folds back right back over top of itself in this area here:





That kind of "self intersecting" surface cannot be used for getting a proper offset or shell.

Basically the mechanism of shelling and offsetting tries to create a surface that is moved by a given distance along the base surface's perpendicular/normal direction.

When there is a collapsed folded area like that, it causes the surface normal to wildly flip around all over the place in that area, creating a kind of chaotic zone for the offset.

You'll need to get the base surface to be more cleanly and simply structured for shelling to work, I'll see if I can think of some suggestions for you, possibly you may want to build a larger dome first, and then use something like a boolean to cut a piece out of it rather than trying to build it all in one go with Network.

- Michael

If I have understood correctly...
Did you like that?

[Edit...ups, sorry Michael, you were faster...]

ok thanks guys

Hi billis, so one possible technique is like the following.

Build a more plain dome like this:



Build a cutting surface similar to this (here I drew a polyline on the bottom plane and then a path curve and used sweep):



Then do a boolean:



Then shell, then do a fillet to round off the sharp parts:



I've attached the model here as billis2.3dm

I'm not sure if that model will work for you, or if you need something a bit different but at any rate this is one technique that could possibly be used.

- Michael

The other thing that you may try is to make a second network that is smaller than the first one and use that as the inside surface rather than trying to do it with shell.

That would be more like building each surface of the final thing individually, sometimes that can be easiest with a shape that has some complex curvy bits that cause problems with offset calculations.

- Michael

ok michael thank u very much for ur precious time
i create the shape i want used 2 others arcs