Additive manufacturing is a process, such as stereolithography, in which objects are created by adding layer after layer from the ground up. This process can be contrasted with subtractive manufacturing, a process in which unneeded material is removed to create the desired object in the same way a sculptor might chisel a block of stone to create a sculpture.
Additive manufacturing is part of the process behind creating almost all 3D printed objects used in medicine. Although additive manufacturing has some disadvantages at present compared to traditional methods of making objects such as injection molding or subtractive manufacturing, it also has some distinct advantages.
Potential disadvantages of the additive process are that at present it is not time or cost-effective to mass-produce objects and the physics of the permitted materials used and how they are built in some cases means that objects created are somewhat weaker than those made in a subtractive process.
Advantages of additive techniques include easier prototyping and customization of objects to specific patients and the ability to create extremely complex, partially hollow objects that could not be created with other methods as well as less material waste.