Hi, I made a box made of three layers in three separate part files. I then combined them together to form a new assembly. I saved the assembly as one SW assembly file. However, when I saved the assembly as a STL file for 3D printing, SW created three separate STL files which correspond to the three part files. Could you please let me know why SW did not save the entire assembly as one STL file and how I can make SW to save the entire assembly as one STL file for 3D printing? Thanks