Dealing with lots of shells I would like to ask if someone here has experience
in creating shells with a change in with, like form 1mm to 2 mms.

Any ideas, any tips ?

Thanl you Tom

Hi Tom, do you have a surface you want to use as the base form? If you could post the .3dm model file of that here, that would probably help me better understand the particular case you're working on.

One method to try though would be to focus initially on building your variable offset height surface over a plane using loft or maybe surface control point manipulation and then apply that plane over your base surface using Transform > Deform > Flow.

- Michael

Hi David, thanks for answering, I attached a file.

Thanks for posting the file. So yes I'd think your best bet would be using Flow, but your base surface there isn't just a simple full surface it's a trimmed surface and Flow only works on a full surface and will ignore the trim. So it's probably best to untrim it and then work on trimming the results later. If you had a cutting surface that you used to trim your surface maybe it would work for cutting both pieces.

So to make the variable offset in the attached file, I prepared 2 planes off to the side and used control point editing to move one point upwards. Then I untrimmed your surface (select all boundary edges and hit delete), then selected the edited plane, ran Transform > Deform > Flow and used the plane underneath as the base surface and your twisty surface as the target surface.

- Michael

You never stop amazing with your support - thank you Michael !