How are physical models created from 3D designs?

When you create physical models from your 2D and 3D CAD designs, you typically follow this process: 

1. Export your CAD models. 
2. Import them into a computer-aided manufacturing or machining (CAM) program. 
3. Use the CAM program to convert your design into “instructions” called G-codes by defining machining parameters.
   G-codes calculate the necessary movement (toolpath) and operation of the tool head to put together the end product. Basically, they instruct a computer numerical control (CNC) machine how to build the physical CAD model out of various materials, using additive and subtractive tools.
4. Run the machining sequence through a post processor so it’s optimized to meet the specific requirements of the CNC machine you’re using.
5. Feed the G-code into the CNC machine controller.
6. The CNC machine creates your models by cutting 2D shapes (laser cutter, 2.5D axis router), milling 3D forms (3+ axis router), or printing 3D objects (3D printer).
   Note that CNC machines are usually compatible with the following CAD formats:
   • 2D: AI, PDF, DXF, and DWG
   • 3D: STL, OBJ, DXF, STEP, IGES, DWG, and 3DM