The CAD file related to this case is attached to this message below. I intended to convert this file format from stl. to step. and essentially the step. file will be used in Starccm for aerodynamics study. Starccm require CAD geometry have on ely ONE body which contain MULTIPLE surfaces. However, I was not able to modify my file in Solidworks to meet this requirement. Right now I am able to export the file as surface body which contain multiple bodies (hundreds of them) and one surface under each body and this is the opposite of what I need. Any thoughts on how to solve this issue? I am looking forward to your reply. Thank you.