STL file format is used because of its flexibility and popularity. Almost any software and hardware supports this file format. This means that you can use your favourite CAD programs,and slicers without any problems.
3D printers supported the .STL extension . You can export this extension from AutoCAD and send it to 3D printer software such as CURA. However, the milling machine has special programs for exporting to GM code such as Mastercam, PowerMill, and SolidCam.