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Additive manufacturing is the cutting edge of materials science. In additive manufacturing (sometimes referred to as 3D printing), 3D objects are constructed layer by layer with specialized equipment, thus minimizing material waste and finish machining. The additive manufacturing equipment receives data from a CAD file and creates an object by adding successive layers of liquid, powder, or sheet material. A wide variety of metals, plastics and composites can be used in the process.
With four decades of materials testing experience, and key Nadcap and A2LA accreditations, WMT&R is uniquely qualified to test materials created using additive manufacturing processes. We are a trusted testing partner for the aerospace primes and other companies in advanced industries such as automotive, medical, and power generation who are leading the adoption of these materials and processes. We have been working closely with the leaders of additive manufacturing to learn more about the characteristics of these materials and advance the additive manufacturing processes.
Most additive manufacturing procedures are fairly similar in process although the method of applying successive layers varies from method to method. Most types of additive manufacturing start with a metal base plate called a substrate onto which the desired part is built. For powder based technologies, a metal powder is spread over the surface and one of several fusing methods is applied in only the desired locations for that cross section. The locations for the beam to fuse are determined by a CNC program. The substrate is then lowered one step and more powder is spread over the surface. This iterative process, as shown in the figure below, is repeated as necessary. The capabilities of additive manufacturing enhance product customization and enable efficient, cost-effective production and delivery.
The method to fuse successive layers varies from process to process, although the two most common methods are sintering and melting. Melting requires higher temperatures because of the need to reach the melting point of the material that is being built, while sintering can be done at a lower temperature. Sintering fuses the material without having to liquefy the powder.
Some of the different types of additive manufacturing are Direct Metal Laser Sintering (DMLS) Direct Metal Laser Melting (DMLM), Selective Laser Sintering (SLS), Selective Laser Melting (SLM), and Electron Beam Melting (EBM). SLS and SLM can refer to any material while DMLS and DMLM refer only to metals. DMLM, DMLS, SLM, and SLS are all very nearly the same process, with the main difference being applicable materials and the temperatures required to fuse the material together. They are commonly done using a Yb-YAG laser and require an inert gas environment such as Argon. EBM uses an electron beam instead of a laser to melt the metal that is being built. EBM can be used on both powdered metals and metal wire. In the case of metal wire, the feed wire is melted and welded in successive layers on a substrate.