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What Are the Different Types of 3D Printing Technologies and 3D Printers?

The first thing you should know is that ‘3D printing’ is actually a sort of ‘catch-all’ term that covers a group of additive manufacturing technologies and processes.

In all, there are ten different types of 3D printing technologies used by 3D printers today.

In this article, we will look at all ten 3D printing technologies and the processes involved with each, their applications, along with their strengths and limitations.

Fused Deposition Modeling
1. Fused Deposition Modeling (FDM),

 sometimes called Fused Filament Fabrication (FFF) is a 3D printing technology that uses a process called Material Extrusion. Material Extrusion devices are the most widely available - and inexpensive - of the types of 3D printing technology in the world today.

 
They work by a process where a spool of filament of solid thermoplastic material (PLA, ABS, PET) is loaded into the 3D printer. It is then pushed by a motor through a heated nozzle, where it melts. The printer’s extrusion head then moves along specific coordinates, depositing the 3D printing material on a build platform where the printer filament cools and solidifies, forming a solid object.

Once the layer is complete, the printer lays down another layer, repeating the process until the object is fully formed. Depending on the object’s complexity and geometry, support structures are sometimes added, for example, if the object has steep overhanging parts.

Common applications for FDM include electrical housings, form and fit testings, jigs and fixtures, and investment casting patterns.

Strengths of FDM are that it offers the best surface finish plus full color along with the fact there are multiple materials available for its use.

It is limited by being brittle, therefore unsuitable for mechanical parts. It also has a higher cost than SLA/DLP.

2. Stereolithography (SLA)

is the world’s first 3D printing technology. It was invented by Chuck Hull in 1986. It works by a 3D printing method called Vat Polymerization where a material called a photopolymer resin (Standard, Castable, Transparent, High Temperature) in a vat is selectively cured by a light source.
 
Specifically, an SLA printer uses mirrors, called galvanometers or galvos, where one is positioned on the X-axis, the other on the Y-axis. These galvos aim the point of a laser beam across the vat of resin, selectively curing and solidifying a cross-section of the object in the build area, building it up layer by layer.

3. Digital Light Processing (DLP)

is a 3D printing technology and is almost the same type of machine as SLA. The main difference being DLP uses a digital light projector that flashes a single image of each layer all at one time - or does multiple flashes for larger parts.

Light is projected onto the resin by light-emitting diode (LED) screens or an ultraviolet (UV) light source, such as a lamp. It is directed onto the build surface by a Digital Micromirror Device (DMD), which is an array of micro-mirrors that control where the light is projected and generate the light pattern on the build surface.

Since the projector is a digital screen, the image of each layer is made up of square pixels, so each layer is formed from small rectangular blocks called voxels.

DLP has faster print times than SLA because each layer is exposed all at once, instead of tracing the cross-section of an area with the point of a laser.

Common applications for SLA and DLP are injection mold-type polymer prototypes, jewelry, dental applications, and hearing aids.

Their strengths are they have fine feature details and smooth surface finish.

They are limited by being brittle, therefore unsuited for use as mechanical parts.

4. Selective Laser Sintering (SLS)

uses a 3D printing process called Power Bed Fusion. A bin of thermoplastic powder (Nylon 6, Nylon 11, Nylon 12) is heated to just below its melting point. Then, a recoating or wiper blade deposits a thin layer of the powder - usually 0.1 mm thick - onto the build platform.

 
A laser beam begins scanning the surface, where it selectively ‘sinters’ the powder, meaning it solidifies a cross-section of the object. As with SLA, the laser is focused on a location by a pair of galvos.

Once the entire cross-section is scanned, the platform moves down by one thickness of layer height and the whole process is repeated until the object is fully manufactured. Powder that is not sintered remains in place supporting the object that has been sintered, eliminating the need for support structures.

Common applications for SLS are the manufacturing of functional parts, complex ducting requiring hollow designs, and low-run production.

Its strengths are in the creation of functional parts, parts with good mechanical properties, and with complex geometries.

SLS is limited by requiring longer lead times and its higher cost when compared with FDM/FFF.

5. Material Jetting (MJ)

is a 3D printing technology whose process goes by the same name. It uses photopolymer resin (Standard, Castable, Transparent, High Temperature) and works in a way similar to the common inkjet printer. The difference is, instead of printing a single layer of ink, multiple layers are built upon one another, creating a solid object.

MJ differs from other types of 3D printing technologies that deposit, sinter, or cure build material with point-wise deposition. Instead, the print head jets hundreds of droplets of photopolymer and cures/solidifies them using UV light. Once a layer is deposited and cured, the build platform lowers by one layer thickness and the process is repeated until the 3D object is built.

Another difference from 3D printing technologies is instead of using a single point to follow a path which outlines the cross-sectional layer, MJ machines deposit build material in a fast, line-wise manner.

The advantage to this is MJ printers can fabricate multiple objects in a single line without affecting build speed. As long as the models are arranged correctly with optimal spacing, MJ can produce parts faster than other types of 3D printer.

Objects made with MJ require support during printing and are printed simultaneously during the build process with a dissolvable material that is removed in post-processing. MJ is one of the only kinds of 3D printing technology that can create objects made from multiple materials and with full color.

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6. Drop on Demand (DOD)

is a kind of 3D printing technology that also uses the Material Jetting process. It uses a pair of inkjets. One deposits the wax-like build material, the second deposits the dissolvable support material. Like other typical kinds of 3D printing technology, a DOD printer follows a predetermined path for jetting material in a point-wise deposition, creating the cross-sectional area of an object layer by layer.

 
DOD printers also use something called a ‘fly-cutter’ which skims the build area after each layer is created, ensuring a perfectly flat surface before starting the next layer.

Common applications for MJ and DOD are full-color product prototypes, prototypes similar to injection molding, low-run injection molds, and medical models.

Strengths are its surface finish, ability to use multiple materials and full color.

Limitations include brittleness making it unsuitable for mechanical parts and a higher cost than SLA/DLP.

7. Sand Binder Jetting

is the 3D printing technology that uses the Binder Jetting process. The process is similar to SLS as it requires an initial layer of powder, in this case, sand or silica, on the build platform. It differs from SLS, in that instead of using a laser to sinter powder, a print head moves over the surface depositing droplets of binder which bind the powder together, producing each layer of the object.

 
Once a layer is printed, the build platform is lowered and a new layer of powder is spread over the just printed layer. The process is repeated until the object is completed.

For full-color models, objects are made using a plaster-based or acrylic powder along with a liquid binding agent. The printhead first jets the binding agent while the second printhead jets the color, allowing for full-color model printing.

After the parts are fully cured, they are taken out of the loose unbonded powder and cleaned. An infiltrant (a fast-curing resin for strengthening 3D printed models) is often introduced to enhance mechanical properties. Coatings can also be added to enhance colors.

Sand Binder Jetting is a low-cost technology for producing parts and sand cast molds and cores. After printing, the cores and molds are removed from the build area and cleaned, removing any loose sand. They are then ready for immediate casting. After casting, the mold is broken apart and the final metal component is removed.

8. Metal Binder Jetting

uses Binder Jetting for the fabrication of metal objects. The metal powder is bound using a polymer binding agent. It allows the production of objects with complex geometries that are far beyond the capabilities of conventional manufacturing techniques.

 
Functional metal objects do require a secondary process like infiltration or sintering, without which the part would have poor mechanical properties.

With infiltration, the metal powder is bound by a binding agent. Once cured, the object is placed in a furnace, where the binder is burned out. This leaves the object at about 60% density, with voids left throughout by the burned-out binder.

Bronze is then added by capillary action to infiltrate the voids, which results in an object of about 90% density and much greater strength. It should be noted objects made by Metal Binder Jetting typically have lower mechanical properties than those made with Powder Bed Fusion.

Common applications for Sand and Metal Binder Jetting are sand casting, functional metal parts, and full-color models.

Strengths include low-cost and large build volumes plus functional metal parts.

A limitation is mechanical properties are not as good as with metal powder bed fusion.

After the parts are fully cured, they are taken out of the loose unbonded powder and cleaned. An infiltrant (a fast-curing resin for strengthening 3D printed models) is often introduced to enhance mechanical properties. Coatings can also be added to enhance colors.

Sand Binder Jetting is a low-cost technology for producing parts and sand cast molds and cores. After printing, the cores and molds are removed from the build area and cleaned, removing any loose sand. They are then ready for immediate casting. After casting, the mold is broken apart and the final metal component is removed.

9. Direct Metal Laser Sintering (DMLS) and Selective Laser Melting (SLM)

are 3D printing technologies that use Metal Powder Bed Fusion, the process where a heat source is utilized to fuse metal particles one layer at a time. Both make objects in a way similar to SLS. The main difference being these technologies are used in the production of metal parts instead of plastic. Typical materials used are metal powder, aluminum, stainless steel, and titanium.

 
DMLS is used for producing parts from metal alloys. Instead of melting it, DMLS heats the metal powder with a laser to the point where it fuses together on a molecular level.

SLM uses the laser to fully melt the metal powder to form a homogeneous part, in other words, it makes parts from single element materials, such as titanium.

Also different from SLS, DMLS and SLM processes do need structural support in order to limit the possibility of distortion which can result from the high temperatures used during printing.

9. Direct Metal Laser Sintering (DMLS) and Selective Laser Melting (SLM)

are 3D printing technologies that use Metal Powder Bed Fusion, the process where a heat source is utilized to fuse metal particles one layer at a time. Both make objects in a way similar to SLS. The main difference being these technologies are used in the production of metal parts instead of plastic. Typical materials used are metal powder, aluminum, stainless steel, and titanium.

 
DMLS is used for producing parts from metal alloys. Instead of melting it, DMLS heats the metal powder with a laser to the point where it fuses together on a molecular level.

SLM uses the laser to fully melt the metal powder to form a homogeneous part, in other words, it makes parts from single element materials, such as titanium.

Also different from SLS, DMLS and SLM processes do need structural support in order to limit the possibility of distortion which can result from the high temperatures used during printing.

10. Electron Beam Melting (EBM)

also uses the Metal Powder Bed Fusion process. Unlike DMLS and SLM, instead of a laser, it uses a high energy beam of electrons for inducing fusion between metal particles in a powder.

 
A focused beam of electrons scans over a thin layer of powder, causing localized melting and solidifying over a particular cross-sectional area. The areas are then built up to create a solid object.

Because of its higher energy density, EBM has a much better build speed than DMLS or SLM. Minimum feature size, powder particle size, layer thickness, and surface finish are generally larger with EBM.

Also, because of the nature of the process, EBM parts must be made in a vacuum and can only be used with electrically conductive materials.

Common applications for these last three 3D printing technologies are functional metal parts for the aerospace, automotive, medical and dental industries.

Strengths are the fabrication of the strongest functional metal parts and the ability to produce complex geometries.

Limitations are high cost and small build sizes.

You are now are familiar with the seven different additive manufacturing processes which have given rise to these ten 3D printing technologies (and an astonishing number of acronyms!) used by 3D printers today.

If you have any more questions about the different types of 3D printing technologies, please visit MakerBot.com today for more information!