Overview
There are many different printing techniques, with many more different synonyms. So while it is impossible to give a complete overview of all the different technologies and their caveats out there, this page aims to give a rough idea of what is out there. Almost all 3D printing technologies can be categorised into one of three main groups:
The first group of 3D printers extrudes a material via a print head nozzle. The material is molten and deposited on the layer underneath, where it hardens again. The most commonly used materials are thermoplastics (polylactic acid (PLA), acrylonitrile butadiene styrene (ABS)), which are deposited with a technique called "Filament Deposition Modelling". Other techniques of note are "Wire and Arc Additive Manufacturing" (used for industrial scale metal prints), as well as "Material Jetting" (which utilises inkjet print heads). Using these techniques, a multitude of materials can be printed, including metal alloys, chocolate, and even wood or ceramic composites.
The second group of 3D printers selectively solidifies photopolymers - liquid materials that harden by exposure to light, typically ultraviolet light delivered via a laser. There are two key technologies: "Stereolithography" and "Poly Jetting". As the name of this group implies, these techniques can only print plastics. Another important technique is "Digital Light Processing", which is very similar to Stereolithography, except that it uses a different kind of illumination.
The third group of 3D printers binds granules of the material by glueing or melting them. This method offers the widest choice of materials: glass, ceramics, many metals, and plastics. The technologies associated with this group are "Binder Jetting" and "Laser Sintering/Melting".
A more extensive overview of the different techniques can be found here.
- Extrusion Printing
- Photopolymerisation
- Powder Binding Techniques
The first group of 3D printers extrudes a material via a print head nozzle. The material is molten and deposited on the layer underneath, where it hardens again. The most commonly used materials are thermoplastics (polylactic acid (PLA), acrylonitrile butadiene styrene (ABS)), which are deposited with a technique called "Filament Deposition Modelling". Other techniques of note are "Wire and Arc Additive Manufacturing" (used for industrial scale metal prints), as well as "Material Jetting" (which utilises inkjet print heads). Using these techniques, a multitude of materials can be printed, including metal alloys, chocolate, and even wood or ceramic composites.
The second group of 3D printers selectively solidifies photopolymers - liquid materials that harden by exposure to light, typically ultraviolet light delivered via a laser. There are two key technologies: "Stereolithography" and "Poly Jetting". As the name of this group implies, these techniques can only print plastics. Another important technique is "Digital Light Processing", which is very similar to Stereolithography, except that it uses a different kind of illumination.
The third group of 3D printers binds granules of the material by glueing or melting them. This method offers the widest choice of materials: glass, ceramics, many metals, and plastics. The technologies associated with this group are "Binder Jetting" and "Laser Sintering/Melting".
A more extensive overview of the different techniques can be found here.
Pros and Cons
Technique |
Pros |
Cons |
Filament Deposition Modelling (FDM) |
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Stereolithography (SLA) |
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Poly Jetting |
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Binder Jetting |
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Laser Sintering/Melting |
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Discussion
Filament Deposition Modelling
In Filament Deposition Modelling a plastic or plastic composite is fed into a hot (~200˚C) print head nozzle, where the material melts. This creates a continuous stream of material which hardens rapidly as it cools down. The nozzle is attached to an xy-stage, which is computer controlled to trace out the desired shape on a heated bed that moves in the z-axis.
There is a wide choice of different composites available. The downside is that the different layers create visible ripples, making it very hard to achieve a smooth finish.
There is a wide choice of different composites available. The downside is that the different layers create visible ripples, making it very hard to achieve a smooth finish.
Stereolithography
In stereolithography an ultraviolet light laser is used to selectively cure parts of a polymer resin. After hardening one layer, the print bed is lowered to cover the piece with a thin layer of uncured resin. This process is repeated to print successive layers.
This way very high resolutions can be achieved, at the cost of slow printing speeds.
This way very high resolutions can be achieved, at the cost of slow printing speeds.
Poly Jetting
As in Stereolithography, a UV light source is used to cure a resin. However, here the liquid polymer is sprayed onto the print, where it is then cured.
This method offers the possibility of using different plastics in the same print, most notably a sacrificial support material that allows the printing of complex geometries, but also multiple plastics in the main print. Even gradual mixing of the components within the print is possible.
This method offers the possibility of using different plastics in the same print, most notably a sacrificial support material that allows the printing of complex geometries, but also multiple plastics in the main print. Even gradual mixing of the components within the print is possible.
Binder Jetting
Binder Jetting is the process of adding a liquid binding material to a bed of powder. This has the advantage that it is very easy to incorporate colour into the print. The disadvantage is that the surface is very rough.
Laser Sintering/Melting
A laser is used to fuse powdered plastics or even metals. The difference between the two methods is that with laser sintering the granules are fused together on a molecular level, whereas the material is fully molten with laser melting. Laser melting is preferentially used for single element materials as opposed to metal alloys. A similar technique is "Electron Beam Melting", where an electron beam is used instead of a laser.
This way, even titanium can be printed, as well as a wide range of other materials. The downside is the price as well as slow printing speed.
This way, even titanium can be printed, as well as a wide range of other materials. The downside is the price as well as slow printing speed.