There are three main categories of 3D printing technologies:

Extrusion (FFF and FDM): a plastic filament is melted and deposited on the build platform of the 3D printer to form the object layer by layer.

Resin (SLA and DLP): a liquid photosensitive resin is cured by a laser or a projector to form the object directly in the resin tank of the 3D printer. The most common 3D printing technology using photopolymerization (solidification of the photosensitive resin via a source of light) is called stereolithography (SLA).

Powder (SLS, SLM, DMLS): a powdered material is sintered or melted by a laser, the grains of powder are bonded or melted together (sintered) to obtain a solid structure. The Selective Laser Sintering (SLS) technology is the most common among powder-based 3D printing technologies, although several derived processes exist.

FDM (Fused Deposit Modelling)

FDM is a 3D printing process developed by Scott Crump, and then implemented by Stratasys Ltd., in the 1980s. It uses production grade thermal plastic materials to print its 3D objects. It’s popular for producing functional prototypes, concept models, and manufacturing aids. It’s a technology that can create accurate details and boasts an exceptional strength to weight ratio.Before the FDM printing process begins, the user has to slice the 3D CAD data (the 3D model) into multiple layers using special software. The sliced CAD data goes to the printer which then builds the object layer at a time on the build platform. It does this simply by heating and then extruding the thermoplastic filament through the nozzle and onto the base. The printer can also extrude various support materials as well as the thermoplastic. For example, as a way to support upper layers, the printer can add special support material underneath, which then dissolves after the printing process. As with all 3D printers, the time it takes to print all depends on the objects size and its complexity. Like many other 3D technologies, the finished object needs cleaning. Raw FDM parts can show fairly visible layer-lines on some objects. These will obviously need hand sanding and finishing after printing. This is the only way to get a smooth, end product with an even surface. FDM finished objects are both functional and durable. This makes it a popular process for use in a wide range of industries, including for mechanical engineering and parts manufacturers

SLA (Stereolithography)

Stereolithography (SLA) is an additive manufacturing process which belongs to the Vat Photopolymerization family. In SLA, an object is created by selectively curing a polymer resin layer-by-layer using an ultraviolet (UV) laser beam. The materials used in SLA are photosensitive thermoset polymers that come in a liquid form.

Stereolithography – more commonly referred to as SLA 3D printing – is one of the most popular and widespread techniques in the world of additive manufacturing. It works by using a high-powered laser to harden liquid resin that is contained in a reservoir to create the desired 3D shape. In a nutshell, this process converts photosensitive liquid into 3D solid plastics in a layer-by-layer fashion using a low-power laser and photopolymerization.

SLA is one of three primary technologies adopted in 3D printing, together with fused deposition modeling (FDM) and selective laser sintering (SLS). It belongs to the resin 3D printing category. A similar technique that is usually grouped with SLA is called digital light processing (DLP). It represents a sort of evolution of the SLA process, using a projector screen instead of a laser.

DLP (Digital Lightening Process)

DLP is the oldest of the 3D printing technologies, created by a man called Larry Hornbeck back in 1987. It’s similar to SLA (see above), given that it also works with photopolymers. The liquid plastic resin used by the printer goes into a translucent resin container. There is, however, one major difference between the two, which is the source of light. While SLA uses ultra violet light, DLP uses a more traditional light source, usually arc lamps. This process results in pretty impressive printing speeds. When there’s plenty of light, the resin is quick to harden (we’re talking seconds). Compared to SLA 3D printing, DLP achieves quicker print times for most parts. The reason it’s faster is because it exposes entire layers at once. With SLA printing, a laser has to draw out each of these layers, and this takes time. Another plus point for DLP printing technology is that it is robust and produces high resolution models every time. It’s also economical with the ability to use cheaper materials for even complex and detailed objects. This is something that not only reduces waste, but also keeps printing costs low.

SLS (Selective Laser Sintering)

An American businessman, inventor, and teacher named Dr. Carl Deckard developed and patented SLS technology in the mid-1980s. It’s a 3D printing technique that uses high power CO2 lasers to fuse particles together. The laser sinters powdered metal materials (though it can utilize other materials too, like white nylon powder, ceramics and even glass). Here’s how it works: The build platform, or bed, lowers incrementally with each successive laser scan. It’s a process that repeats one layer at a time until it reaches the object’s height. There is un-sintered support from other powders during the build process that surround and protect the model. This means the 3D objects don’t need other support structures during the build. Someone will remove the un-sintered powders manually after printing. SLS produces durable, high precision parts, and it can use a wide range of materials. It’s a perfect technology for fully-functional, end-use parts and prototypes. SLS is quite similar to SLA technology with regards to speed and quality. The main difference is with the materials, as SLS uses powdered substances, whereas SLA uses liquid resins. It’s this wide variety of available materials that makes SLA technology so popular for printing customized objects.

SLM (Selective Laser Melting)

SLM made its debut appearance back in 1995. It was part of a German research project at the Fraunhofer Institute ILT, located in the country’s most western city of Aachen. Like SLA (see above), SLM also uses a high-powered laser beam to form 3D parts. During the printing process, the laser beam melts and fuses various metallic powders together. The simple way to look at this is to break down the basic process like thus:

Powdered material + heat + precision + layered structure = a perfect 3D object.

As the laser beam hits a thin layer of the material, it selectively joins or welds the particles together. After one complete print cycle, the printer adds a new layer of powered material to the previous one. The object then lowers by the precise amount of the thickness of a single layer. When the print process is complete, someone will manually remove the unused powder from the object. The main difference between SLM and SLS is that SLM completely melts the powder, whereas SLS only partly melts it (sinters). In general, SLM end products tend to be stronger as they have fewer or no voids.

A common use for SLM printing is with 3D parts that have complex structures, geometries and thin walls. The aerospace industry uses SLM 3D printing in some of its pioneering projects. These are typically those which focus on precise, durable, lightweight parts. It’s a costly technology, though, and so not practical or popular with home users for that reason. SLM is quite widespread now among the aerospace and medical orthopaedics industries. Those who invest in SLM 3D printers include researchers, universities, and metal powder developers. There are others too, who are keen to explore the full range and future potential of metal additive manufacturing in particular.

EBM (Electron beam melting)

A Swedish company called Arcam AB founded EBM® in 1997. This is a 3D printing technology similar to SLM (see above), in that it uses a powder bed fusion technique. The difference between the two is the power source. The SLM approach above uses high-powered laser in a chamber of noble, or inert gas. EBM, on the other hand, uses a powerful electron beam in a vacuum. Aside from the power source, the remaining processes between the two are quite similar. EBM’s main use is to 3D print metal parts. Its main characteristics are its ability to achieve complex geometries with freedom of design. EBM also produces parts that are incredibly strong and dense in their makeup.

Here are a few of EBM’s other impressive features:

Doesn’t need extra auxiliary equipment for the 3D printing process

Has increased efficiency using raw materials

Lessens lead times resulting in parts getting to market faster

Can create fully functional, durable parts on demand for wide-ranging industries.

LOM (Laminated object manufacturing)

A Californian company called Helisys Inc. (now Cubic Technologies), first developed LOM as an effective and affordable method of 3D printing. A US design engineer called Michael Feygin—a pioneer in 3D printed technologies—originally patented LOM. LOM is a rapid prototyping system that works by fusing or laminating layers of plastic or paper using both heat and pressure. A computer-controlled blade or laser cuts the object to the desired shape. Once each printed layer is complete, the platform moves down by about 1/16th of an inch, ready for the next layer. The printer then pulls a new sheet of material across the substrate where it’s adhered by a heated roller. This basic process continues over and over until the 3D part is complete. According to Wikipedia, the LOM printing works as follows:

Sheet is adhered to a substrate with a heated roller.

Laser traces desired dimensions of prototype.

Laser cross hatches non-part area to facilitate waste removal.

Platform with completed layer moves down out of the way.

Fresh sheet of material is rolled into position.

Platform downs into new position to receive next layer.

The process is repeated.

It might not be the most popular method of 3D printing today, but LOM remains one of the fastest nonetheless. It’s also perhaps the most affordable method for creating 3D prototypes. The reason for this is because of the low cost of materials used (papers and plastics). It’s also a process that can create fairly large 3D printed objects. Those who continue to use LOM printers today include architects, artists, and product developers.

BJ TECHNOLOGY (Binder Jetting)

The Massachusetts Institute of Technology (MIT) first invented BJ 3D printing. You may also hear this technology referred to in other names, including:

• Powder bed printing
• Inkjet 3D printing
• Drop-on-powder

Binder jetting (BJ). This is the most popular name and the one we’ll use to refer to it.

BJ is a 3D printing process that uses two types of materials to build objects: a powder-based material (usually gypsum) and a bonding agent. As the name suggests, the “bonding” agent acts as a strong adhesive to attach (bond) the powder layers together. The printer nozzles extrude the binder in liquid form similar to a regular 2D inkjet printer. After completing each layer, the build plate lowers slightly to allow for the next one. This process repeats until the object reaches its required height.

The four popular materials used in BJ printing include:

• Ceramics
• Metals
• Sand
• Plastics

It’s not possible to get super high-resolution or overly rugged 3D objects with BJ printing, but there are other advantages. For example, these printers allow you to print parts in full colour. To do this, you simply add colour pigments to the binder, which typically include black, white, cyan, yellow, and magenta. This technology is still advancing, so expect more great things to come in the future. At the time of writing, some applications of BJ 3D printing include rapid prototyping, and various uses in the aerospace, automotive, and medical industries.

Material Jetting (MJ) Polyjet and Wax Casting Technology

You will also hear Material Jetting referred to as wax casting. Unlike other 3D printing technologies, there isn’t a single inventor for MJ. In fact, up until recent times it’s been more of a technique than an actual printing process. It’s something jewellers have used for centuries. Wax casting has been a traditional process where the user produces high-quality, customizable jewellery. The reason it gets a mention here is because of the introduction of 3D printing. Thanks to the arrival of this technology, wax casting is now an automated process. Today, MJ 3D printers produce high-resolution parts, mainly for the dental and Jewellery industries, For jewellers who want to experiment with various casts—as most jewellers do—MJ is now their leading 3D technology. At the time of writing, there are a few high-quality professional wax 3D printers on the market. Here’s how they work: