Hi Michael,

thank you for the fast answer.
The solution you mentioned works correctly but Rhino gets very slow and for many layers, block´s and objects its not the best way.
I think i will do it like i said in my post, save all layers as an .3dm and merge them afterwards.
There is a well working skript on "McNeel Wiki" which batches the .3dm layer export. It's called "Export Layer Objects".

Thank you anyways!
Cheers
Thomas