Additive Manufacturing
= ASTM International defines Additive Manufacturing as the “process of joining materials to make objects from 3D model data, usually layer upon layer, as opposed to subtractive manufacturing methodologies. (ASTM F2792-10, June 2010)
Description
"Traditional manufacturing has fueled the industrial revolution that has enabled our world today, yet it contains inherent limitations that point to the need for new approaches.
Manufacturing comes from the French word for “made by hand.” This etymological origin is no longer appropriate to describe the state of today’s modern manufacturing technologies, however. Casting, forming, molding, and machining are complex processes that involve tooling, machinery, computers, and robots. Similar to a child cutting a folded piece of paper to create a snowflake, these technologies are “subtractive” techniques, in which objects are created through the subtraction of material from a workpiece. Final products are limited by the capabilities of the tools used in the manufacturing processes.
By contrast, AM is a group of emerging technologies that create objects from the bottom-up by adding material one cross-sectional layer at a time.1 Revisiting the childhood analogy, this is conceptually similar to creating an object using building blocks or Legos.
The AM process begins with a 3D model of the object, usually created by computer-aided design (CAD) software or a scan of an existing artifact. Specialized software slices this model into cross-sectional layers, creating a computer file that is sent to the AM machine. The AM machine then creates the object by forming each layer via the selective placement (or forming) of material. Think of an inkjet printer that goes back over and over the page, adding layers of material on top of each other until the original works are 3D objects.
There are several AM processes that are differentiated by the manner in which they create each layer. One technique known as “Fused Filament Fabrication” involves extruding thermoplastic or wax material through heated nozzles to create a part’s cross sections.2 Filament feedstock is guided by a roller into a liquefier that is heated to a temperature above the filament’s melting point. The material is then able to flow freely through the nozzle. When the material reaches the substrate, it cools and hardens. Once the layer is complete, the build platform is lowered one layer-thickness by the Z-stage and deposition of the next layer begins. A secondary sacrificial material may also be deposited (and later removed) in order to support the construction of overhanging geometries. \ Other AM technologies use different techniques for creating each layer. These range from jetting a binder into a polymeric powder (3D Printing), using a UV (ultraviolet) laser to harden a photosensitive polymer (Stereolithography), to using a laser to selectively melt metal or polymeric powder (Laser Sintering).Moreover, recent developments in the synthesis of end-use products allow for increasing numbers of materials to be used simultaneously. Think of an inkjet printer with six color cartridges printing simultaneously—but with different materials such as various metals, plastics, and ceramics in each cartridge." (http://www.acus.org/files/publication_pdfs/403/101711_ACUS_3DPrinting.PDF)