Six Dominant Types of 3D Printing Technologies?

3D printing or additive manufacturing, is a general term that covers a group of technologies and processes. Below please find six different types of technologies used in 3D printing today:

Fused Deposition Modeling (FDM)

Stereolithography (SLA)

Selective Laser Sintering (SLS)

Digital Light Processing (DLP)

Selective Laser Melting (SLM)

Electron Beam Melting (EMB)

Now we will take a closer look at the six most popular 3D printing types from the perspectives of applications, strengths and limitations.

Fused Deposition Modeling (FDM)

FDM or fused filament fabrication (FFF) involves a critical process called material extrusion, where solid thermoplastic material (PLA, ABS, PET) is loaded into the 3D printer and then it melts after being pushed by a motor via a heated nozzle. Finally, the printer filament is extruded on a build platform forming a solid object layer by layer.

FDM uses production-grade thermoplastics, so items printed have excellent mechanical, thermal and chemical attributes. It is commonly used for producing electrical enclosure, fixtures, and investment casting patterns.

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

Stereolithography (SLA)

SLA is the world’s earliest 3D printing technology, featuring fast prototyping process, high accuracy and precision.

The photopolymers are first heated into a semi-liquid form, and then it is converted into solid 3D objects layer by layer, using an ultra violet laser, directed by X and Y scanning mirrors. After the 3D part cools and solids on the platform, it will bathe in chemicals and then be post-cured in an ultra violet oven to make the finished item stronger and more stable.

SLA printing has become a favored economical choice for a wide variety of industries, including automotive, medical, aerospace and entertainment.

Selective Laser Sintering (SLS)

SLS is a technique that uses high power CO2 lasers as power supply to form strong 3D printed objects. The most notable difference between SLS and SLA is that it uses powdered material in the vat rather than liquid resin in a cube, like SLS does.

A bin of thermoplastic powder (Nylon 6, Nylon 11, Nylon 12 or powdered metal materials) is sintered by the laser. It is a repeated process where a laser beam scans a cross-section or one layer at a time. Powder that is un-sintered remains in place supporting the structure that has been sintered.

Thanks to the wide variety of available materials, SLS is quite popular in manufacturing functional parts, and parts with good mechanical properties and complex geometries.

Digital Light Processing (DLP)

Digital Light Processing machines technologies are very similar to SLA. The major difference is that DLP uses a digital light projector to flash a single image of each layer all at once (or multiple flashes for larger parts).

Since an entire layer is exposed all at once, rather than tracing the cross-sectional rectangular blocks called voxels, DLP machines works more efficient than SLA.

Due to the strengths of fine feature details and smooth surface finish, DLP is commonly applied to produce injection mold-type polymer prototypes, jewelry, dental applications, and hearing aids. Limited by being brittle, DLP machines are not suitable for manufacturing mechanical parts.

Selective Laser Melting (SLM)

To some extent, SLM is a subcategory of selective laser sintering (SLS). The SLM process, however, has the ability to fully melt the metal material into a solid three-dimensional part compared with SLS.

Just like SLS, SLM is a powder-based additive manufacturing process that produces three-dimensional (3D) functional parts from CAD data by complete melting of the powder occurs instead of sintering or partial melting. First, a thin layer of powder thickness ranging from 50 to 75 μm was deposited across a substrate platform, where a high-power fiber laser scans the powder surface. Then the powder particles are melted by the heat generated by the fiber laser. Fresh layers of powder are consistently deposited after the previous layer has been scanned. In order to remove oxygen from the cavity, SLM parts should be finished in an inert gas atmosphere such as argon. Loose powders, substrate and supports are removed from the chamber once the whole process completes.

Electron Beam Melting (EMB)

The EBM process refers to a type 3D printing mainly for fabricating metal parts, utilizing a high-power electron beam to heat the raw material (metal powder or wire) under a vacuum atmosphere. The raw materials are fused together by the generated heat. This technique sets EMB apart from SLS, since the raw material fuses having completely melted.

Given EBM 3D printers and powders are expensive, it's no wonder this technology isn't yet utilized for mass production. Instead, it's used for manufacturing high strength metal parts which usually feature a complex structure, which is applied in lots of fields, including medicine, aeronautics, and motorsports.