mechanica

Hi guys, using WF5.

Just started using WF5 mechanica and playing around. I created a 2000mm long section of rectangular hollw section steel.

100mm sq. with a 4mm wall section. Created this using a surface then thickened the section.

If i then try and set up shells using mid planes it tells me i do not have constant thickness for this to happen no matter what i choose.

I didn't have this issue with WF4 so any clues as to what i am doing wrong.

If i just leave it as a surface and don't thicken it and just use shell it works fine. But how do you know once you give the thickness parameter that the model creates a mid plane for the mess.

TIA.