If I run the macro sometimes it comes sometimes not.

The error is here, it has something to do with sw.Doc I think.

bDocWasVisible = swDoc.Visible

swApp.ActivateDoc swDoc.GetPathName
 

Attached is the code as a text file. If one wants to run it you have to open an assembly (or part) in solidworks.

And you need to have a folder "K:\\Konstruk\\temp\\STPundDWG\\" or you change this path

in line EingegebenerDateiPfad_2 = "K:\\Konstruk\\temp\\STPundDWG\\" to a path that exists on your drive.

Thank you.