Additive manufacturing technology is constantly evolving and new processes are researched and unveiled frequently. However, to standardise the industry, the American Society for Testing and Materials (ASTM) group “ASTM F42 – Additive Manufacturing”, in 2010, classified the gamut of Additive Manufacturing technology into 7 types.
Here, we look at the different types of additive manufacturing technologies:
Fused deposition modelling (FDM) is one of the most common and widely used additive manufacturing technology. FDM was trademarked by Stratasys Inc., and hence the separate name Fused filament fabrication (FFF) is used to avoid infringement issues.
In this method, material in a filament form is drawn through a nozzle, is heated and then extruded and deposited onto the build platform in a layer-by-layer process. FFF 3D Printers are most commonly Cartesian type where the nozzle moves in X & Y-direction whereas the build platform moves in the Z-direction.
Extrusion 3D printers are inexpensive and offer quick prototyping of simple parts. It is usually used for printing household items, characters, toys, games and other similar products. The parts have rough surface finish as the maximum resolution is around 100 microns.
Vat Photopolymerisation uses a vat of liquid photosensitive polymer resin. This resin hardens on exposure to UV light. This property is used to build objects layer-by-layer.
A vat filled with the liquid photopolymer resin is exposed to UV light in a controlled environment and the geometry of the object to be printed is traced out. The exposed resin hardens (called curing) and a solid layer is formed. This process continues till the complete object is printed.
The resins are polymer compound with additives for specific applications like Tough, Flexible, Dental, etc. These processes impart high quality surface finish to the object. Most common process in this category are Stereolithography (SLA) and Digital Light Processing (DLP) and even Carbon’s trademarked Digital Light Synthesis (DLSTM) based on its patented technology called Continuous Liquid Interface Production (CLIP).
Powder Bed Fusion
Powder-bed fusion (PBF) is an additive manufacturing technology which fuses powdered material to additively create/build 3D objects. Other technologies which operate on this principle are Selective Laser Sintering (SLS), Direct Metal Laser Sintering (DMLS), Selective Laser Melting (SLM), Electron Beam Melting (EBM), and Selective Heat Sintering (SHS).
The Powder-bed fusion process uses a laser or an electron beam to sinter, melt and fuse the powder particles together while it traces the cross-section of the object to be created. On completion of the first layer, the powder dispensing unit spreads a new layer of powder onto the build platform and the printing continues for the next layer. This process continues till the complete object is built.
Material Jetting process operates in a similar way a regular two-dimensional inkjet printer works. Material in the form of liquid droplets is dispensed from multiple printheads similar to those in an inkjet printer. The material is photosensitive polymer which hardens on exposure to UV light thereby building the part layer-by-layer.
This additive manufacturing technology is used for building parts with high dimensional accuracy and smooth surface finish. In fact, parts can be printed in glossy as well as matte finish with equal accuracy. It is a multi-material technology which enables full-colour printing. The technology is also called as Drop-on-Demand (DOD) as it uses printheads which dispense liquid material to create wax-like parts. It is mostly used for creating investment casting patterns
Binder Jetting is similar to material jetting but it uses two materials in place of one. The two materials include a powdered base material and a binder material. The binder is dispensed on to the powdered material in the build chamber and acts as the binding agent for adhesion of individual layers.
The binder is usually liquid and is dispensed from printheads which move in X & Y-direction. The binder drops the binder as per the geometry of the object to be built. After each layer of printing, the build chamber drops down and a new layer of powder is spread on top of the previous layer and the printhead again traces the cross-section of the object and binds the previous and current layer together.
This process is relatively fast but BJ parts are not recommended for use in structural applications. The unused powder acts as a support to the object and it as such does not need any support structure.
Also Read: How Binder Jetting Works?
The Sheet Lamination process includes two types of manufacturing techniques, Ultrasonic Additive Manufacturing (UAM) and Laminated Object Manufacturing (LOM).
In Ultrasonic Additive Manufacturing (UAM), sheets or ribbons of metal are bound together using ultrasonic welding. After the welding, the part does not require any additional step of machining or removal of material. Different metals like aluminium, copper, steel, and titanium can be joined together which allows for greater flexibility in strength requirement of the part. It requires relatively less energy as the metals are not melted.
Laminated Object Manufacturing (LOM) uses sheets of paper as the base material and adhesive in place of welding. The paper is fed with the help of rollers and a laser traces the cross-section of the object. It uses a cross-hatch method during the printing process so the completed part is easy to remove. Objects manufactured using LOM are not fit for structural use and can only be used for aesthetic purpose.
Directed Energy Deposition
Directed Energy Deposition (DED) is an additive manufacturing technology used for 3D printing of metal and alloys. It can be used for polymers, glass and ceramics but is not popularly used for those materials.
In DED, a nozzle holds a material in a wire form which is known as a feed which moves across multiple axis and an electron beam projector which melts the feed as it moves across while tracing the object geometry. As it uses a laser, DED method is also called as Laser engineered net shaping, 3D laser cladding, directed light fabrication or direct metal deposition.
In DED process the nozzle supplying the material is not restricted to any specific axis but can be moved is various angles due to 4 to 5 axis machines. This method is not only used to build new objects but it is also used for adding materials to existing models for repairs.
This additive manufacturing technology uses materials like Titanium, Cobalt Chrome and Tantalum (a rare metal). The most common application of DED method is in Aerospace and automotive industries.
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