Step-by-step guide

  1. We export our object to STL by selecting the object and going to File>Export Selected > Choose STL* > choose a file name > Save > Binary + uncheck export open objects > ok
    1. Binary or ASCII
      1. STL files can store information in two different ways. These are Binary encoding and ASCII encoding. Binary files are smaller and easier to share, while ASCII files are visually easy to read and check.
      2. The binary format is recommended for 3D printing. However, ASCII format is suggested for those who want to manually inspect STL files for debugging.

Rhino Tips for reducing the file size: 

MeshRepair

ReduceMesh