Hi Simon, it's hard to tell from a written description, can you please post the .3dm model file with the objects you are trying to boolean?

You can get that type of behavior if the objects being booleaned are not closed solids, or if they have any areas of self intersection where an edge or a surface folds back over itself.

Also Shell in MoI for thickening an open surface only works very well if the surfaces are smooth.

If you can post the file that would help to give you more specific information on what's going on in this particular case.

- Michael

THanks Michael.
Hopefully I have uploaded it right. Didnt work the first time.

I want to remove the red shapes from the cyan cone.

Sime.

Hi Simon, the problem was that shell made a bad result, the inner shell surface is kind of mangled.

Instead of shell you'll get a better result in this case making a profile curve like this and then revolving it:



That's what I did with the attached 3DM file which should now boolean ok.

I am planning on overhauling Shell to use the ACIS library which should make it a lot more reliable.

- Michael

Thank you Michael.
That works.

Simon.