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Additive manufacturing technologies: An overview
Written by Ben Redwood
Selecting the most suitable Additive Manufacturing (AM) process for a particular application can be difficult. The very large range of available 3D Printing technologies and materials often means that several of them may be viable, but each offers variations in dimensional accuracy, surface finish and post-processing requirements.
The goal of this article is to categorize and summarize the differences between each of the Additive Manufacturing technologies. We identified the most popular 3D printing processes and the most common applications and materials for each of them.
Photopolymerization occurs when a photopolymer resin is exposed to the light of a specific wavelength and undergoes a chemical reaction to become solid. More details about the photopolymerization mechanism can be found here. A number of additive technologies utilize this phenomenon to build up a solid part one layer at a time.
Vat polymerization processes are excellent at producing parts with fine details and gives a smooth surface finish. This makes them ideal for jewelry, low-run injection molding and many dental and medical applications. The main limitations of vat polymerization is the brittleness of the produced parts.
|SLA||Formlabs, 3D Systems, DWS||Standard, tough, flexible, transparent, & castable resins|
|DLP||B9 Creator, MoonRay||Standard & castable resins|
|CDLP||Carbon3D, EnvisionTEC||Standard, tough, flexible, transparent, & castable resins|
Explore the most popular material options for Vat Photopolymerization
Powder Bed Fusion
Powder Bed Fusion (PBF) technologies produce a solid part using a thermal source that induces fusion (sintering or melting) between the particles of a plastic or metal powder one layer at a time.
Most PBF technologies employ mechanisms for spreading and smoothing thin layers of powder as a part is constructed, resulting in the final component being encapsulated in powder after the built is complete.
The main variations in PBF technologies come from the differing energy sources (for example lasers or electron beams) and the powders used in the process (plastics or metals).
Polymer-based PBF technologies offer a lot of design freedom, as there is no need for support, allowing the fabrication of complex geometries.
Both metal and plastic PBF parts typically have a very high strength and stiffness and mechanical properties that are comparable (or sometimes even better) than the bulk material. There is a large range of post-processing methods available, meaning that PBF parts can have a very smooth finish and, for this reason, they are often used to manufacture end products.
The limitations of PBF often center around surface roughness and internal porosity of the as-printed parts, shrinkage or distortion during processing and the challenges associated with powder handling and disposal.
|SLS||EOS, Stratasys||Nylon, alumide, carbon-fiber filled nylon, PEEK, TPU|
|SLM/DMLS||EOS, 3D Systems, Sinterit||Aluminum, titanium, stainless steel, nickel alloys, cobalt-chrome|
Similar to how toothpaste is squeezed out of a tube, material extrusion technologies extrude a material through a nozzle and onto a build plate. The nozzle follows a predetermined path building layer-by-layer.
Material extrusion is a quick and cost-effective way of producing plastic prototypes. Industrial FDM systems can also produce functional prototypes from engineering materials. FDM has some dimensional accuracy limitations and is very anisotropic.
|FDM||Stratasys, Ultimaker, MakerBot, Markforged||ABS, PLA, Nylon, PC, fiber-reinforced Nylon, ULTEM, exotic filaments (wood-filled, metal-filled etc)|
Explore the most popular material options for Material Extrusion
Material jetting is often compared to the 2D ink jetting process. Photopolymers, metals or wax that cure or harden when exposed to UV light or elevated temperatures can be used to build parts one layer at a time. The nature of the material jetting process allows for multi-material printing. This ability is often used to print support from different (soluble) material during the build phase.
Material jetting is ideal for realistic prototypes, providing excellent details, high accuracy, and smooth surface finish. Material jetting allows a designer to print in multiple colors and multiple materials in a single print. The main drawbacks of material jetting technologies are the high cost and the brittle mechanical properties of the UV activated photopolymers.
|Material jetting||Stratasys (Polyjet), 3D Systems (MultiJet)||Rigid, transparent, multi-color, rubber-like, ABS-like. Multi-material and multi-color printing available|
|NPJ||Xjet||Stainless steel, ceramics|
Binder jetting is the process of dispensing a binding agent onto a powder bed to build a part one layer at a time. These layers bind to one another to form a solid component.
Ceramic-based Binder Jetting is ideally suited for applications that showcase aesthetics and form: architectural models, packaging, ergonomic verification etc. It is not suitable though for functional prototypes, as the parts are very brittle. Ceramic-based Binder Jetting can also be used to create molds for sand casting.
Metal binder jetting parts can be used as functional components and are more cost-effective than SLM or DMLS metal parts, but have poorer mechanical properties.
|Binder jetting||3D Systems, Voxeljet||Silica sand, PMMA particle material, gypsum|
|ExOne||Stainless steel, ceramics, cobalt-chrome, tungsten-carbide|
Direct Energy Deposition
Direct Energy Deposition (DED) creates parts by melting powder material as it is deposited. It is predominantly used with metal powders or wire and is often referred to as metal deposition.
DED technologies are used exclusively in metal additive manufacturing. The nature of the process means they are ideally suited for repairing or adding material to existing components (such as turbine blades). The reliance on dense support structures make DED not ideally suited for producing parts from scratch.
|LENS||Optomec||Titanium, stainless steel, aluminum, copper, tool steel|
|EBAM||Sciaky Inc||Titanium, stainless steel, aluminum, copper nickel, 4340 steel|
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