7 types of Additive manufacturing


In simple layman’s language additive manufacturing or commonly known as 3D printing is a manufacturing process in which a variety of chosen material to meet specific needs is laid down layer by layer to form a three-dimensional object. There are seven  main additive manufacturing types of technologies viz Vat photopolymerisationMaterial ExtrusionMaterial JettingBinder JettingPowder bed fusionDirect energy deposition and Sheet lamination.

Additive manufactured heat exchanger
Figure 1 Additive manufactured heat exchanger ( credit:GE Additive)

Brief history of Additive manufacturing

This unique 3D printing technology creates physical 3D objects in 7 steps by converting digital files either created on a Computer-aided design (CAD), Computer-aided manufacturing (CAM) program or a 3D scanner.
Chuck Hull an American engineer of 3D Systems corporation is accredited with inventing 3D printing in 1983 known as solid imaging process called as stereolithography (3D Printing), the first commercial rapid prototyping technology and also the STL file format. Thanks to Hull his contribution of STL file format, digital layer slicing and infill strategies are still being used in many additive manufacturing processes today.

More than enough statistics support the claim that the introduction of 3D Printing has revolutionized the industrial world in a way no other product has achieved this momentous success in the last 35 years.

There are many different 3D printing processes floating about but technically all those additive manufacturing technologies can be divided into following 7 major categories.

Vat photopolymerization

This process uses a technique called Photopolymerization in which radiation curable resins or photopolymers are used to create three-dimensional objects by selectively exposing them to ultraviolet light. When exposed these materials undergo a chemical reaction and become solid.

Stereolithography parts
Figure 2 Stereolithography parts (image credit – Formlabs )

There are three main types under this category – Stereolithography, Digital Light Processing and Continuous Digital Light Processing.

Powder bed fusion

Powder bed fusion processes especially the selective laser sintering is one of the early industrial additive manufacturing techniques. This method uses a laser or electron beam to melt the powdered material and fuse them together to create a solid object.

Powder bed fusion part
Figure 3 Powder bed fusion part( image credit:GE)

Direct metal laser sintering, Selective laser sintering, Multi Jet Fusion, Electron beam melting, Selective laser melting and Selective heat sintering are the main types of powder bed fusion.

Binder jetting

Binder jetting uses a binding agent usually in liquid form and selectively deposits onto powdered material. The print head and a powder spreader deposit alternating layers of bonding agent and build material to form a 3d object.

Binder jetting part
Figure 4 Binder jetting part ( image credit – ExOne®)

Material extrusion

Material extrusion was originally developed and patent by S. Scott Crump under Fused Deposition Modelling (FDM) in the 1980s. In this additive manufacturing technique, the continuous filament of thermoplastic is fed through a heated nozzle, before deposited layer by layer onto the build platform to create the object.

Material extrusion (FDM) part
Figure 5 Material extrusion (FDM) part ( image credit: .stratasys.com)

Directed energy deposition (DED)

Directed energy deposition technology uses focused thermal energy to melt and fuse the material together as they are deposited to create a 3d object. These are very similar to welding process but very finely detailed.

Directed energy deposition part
Figure 6 Directed energy deposition part ( image credit:DMG MORI)

In this process commonly, laser or electron beam is used as focused thermal energy and can be subdivided into LENS and EBAM.

Material jetting

This additive manufacturing technique is very similar to common inkjet printers where the material droplets are deposited layer by layer selectively to create a three-dimensional object. Once a layer is complete, its cured by ultraviolet light.

Poly jetting or material jetting part
Figure 7 Poly jetting or material jetting ( image credit: https://www.stratasys.com/polyjet-technology)

Drop on demand and nanoparticle jetting are two of the common types of material jetting printers.

Sheet lamination

Sheet lamination technology is an umbrella term for the Ultrasonic Additive Manufacturing, Selective Deposition Lamination and Laminated Object Manufacturing. All these technologies use sheets of material to create 3D objects by stacking them and laminating them using either adhesive or ultrasonic welding. Once the object is built the unwanted areas of the sections are removed layer by layer.

Sheet lamination part
Figure 8 Sheet lamination part ( image credit – https://www.mcortechnologies.com/hall-fame-mcor-models/)

Further reading