STL Error

@ehsan_pazooki , 

Try importing the file with units "inches", this still results in errors, but the model is visible. Here is what I tried https://cad.onshape.com/documents/6f366ec3b76d2bc261faecfb/w/d9c0deced1fc1229b48c2946/e/3a0816f0ddf91d7d090222dd

When importing files, Onshape typically expects the meshes to be watertight with reasonable tolerances and without intersections etc.. hence you see the error.