Circular hole in a cylindrical wall

[120391]

Hi. My problem is that i can't figure out the way to make a circular hole in a cylindrical wall. I tried to use option with combining two objects (i've attached a file in which i tried to cut a hole in a cylindrical wall using another cylinder) but i don't know if it's right direction. When im trying to subtract one object from another Robot gives me "not a body get" error. Is there any way to do it right ? Robot file

[Rafal.Gaweda]

Check this:

http://forums.autodesk.com/t5/Autodesk-Robot-Structural/Shell-problem-opening/m-p/3783117/highlight/...

[120391]

So i've done everything like in the instruction and after a quite long time of waiting this is the result : 

Any idea what am I doing wrong ?

Edit : Ok got it right this time. Everything is quite ok , but if i try to get a circular shape i need to make a really dense mesh and it takes forever for my computer to connect those objects. I've waited some time and he did it but then i wanted to mesh the result (object with hole) and Robot does the whole connecting procedure again. So now everytime i change something (add new load and want to get actual results for an example) Robot will be connecting those objects again ?