Additive manufacturing, or 3D printing is the process of making a three dimensional design into an actual 3D model. On the other end, machining is a subtractive manufacturing process where you begin with a piece of material and cut away until you arrive at the desired part of geometry. Essentially, you are subtracting material to get the desired part shape. An example of additive manufacturing is 3D printing where material is “printed” in the shape of the part. A part is built in 2D layers. Think of an ink jet printer, but instead or printing ink, it is printing plastic and each layer of 2D geometry has some thickness, say .005”. The print head raises (3D) such that each layer is printed one of top of the other. There are a number of additive process other than 3D printing and the breadth of materials that can be printed is expanding quickly.