Exporting simplified assemblies

  Question

In order to send models to customers I have been trying to use the simplified assembly command so they cannot break down the component parts. I can create a simplified assembly which consists of a number of the part copy surfaces and can save this as a part file. What I cannot find out is how to save the part as a STEP file. Each time I try it states that there is no design body in the file and does not export anything.