Types of 3D Printing Explained 

Most people associate 3D printing with the very cutting-edge technology, though it has actually been around since the 1980s! But, thanks to the recent advances made in the machinery, the materials, and the software they use, it has become an attractive and viable option for a much broader range of industries. 

However, that technological background is still front-and-center when it comes to the terminology. SLS and DLP. EBM and MJF. With all those acronyms flying around it, you can get a migraine just by looking at them! It can seem a daunting and impenetrable subject to understand. But it shouldn’t be. This article will quickly clarify exactly what 3D printing is, and then give you a solid beginners-guide to the different types used (going easy on the jargon!), plus the most common materials used and applications, so you can make an informed decision whether it’s right for you and your business.

What Is 3D Printing? 

3D printing - also known as additive manufacturing (AM) - uses CAD (computer-aided design) to create three-dimensional parts. It does this by adding materials together layer by layer until the new physical product is created.

The term “3D printing” is an umbrella term that includes a range of different 3D processes, and these processes are responsible for the selection of other technologies we use today. There are eight categories in total, and they are:

• Stereolithography (SLA)
• Selective Laser Sintering (SLS)
• Fused Deposition Modeling (FDM)
• Digital Light Process (DLP)
• Multi Jet Fusion (MJF)
• PolyJet
• Direct Metal Laser Sintering (DMLS)
• Electron Beam Melting (EBM)

Selecting which is best for you requires an understanding of their respective strengths and weaknesses, then matching them to the needs of your product. And that’s precisely what this article is here to help you do!

Types of 3D Printing 

1. STEREOLITHOGRAPHY (SLA) 

Stereolithography has the distinction of being the world’s first 3D printing technology, and while many types have fallen by the wayside, it remains a popular choice. 

Unlike your household desktop printer that squeezes ink onto the surface, SLA printers use an excess of liquid plastic, which is then cured by a laser into hardened plastic (‘photopolymerization’). Then the printer drops down to form another layer, then another, until the product is complete. It’s then rinsed with a solvent and put in an ultraviolet oven to finish the process.

Small items can be printed in 6-8 hours, while larger prints can take a few days. 

Its precise nature and accuracy are what make it such a popular choice, particularly for industries that require tight tolerances, fine features, and smooth surfaces- such as molds, patterns, and functional parts. 

Stereolithography is ideal for rapid prototyping, concept modeling, and short-run productions.

2. SELECTIVE LASER SINTERING (SLS)

Laser sintering- also known as laser melting- refers to laser-based 3D printing that works with powders (as opposed to the liquid resin used by stereolithography).

The laser traces across a bed of tightly-compacted powdered material, as directed by the data fed to the machine. As the laser interacts with the surface, it ‘sinters’ (fuses) the particles together to form a solid. Again, subsequent layers are formed and fused to deliver the finished product. The powder bed is then removed, any excess powder removed, and the printed part remains.

Because the powder bed serves as a support structure for overhangs and undercuts, it enables the manufacturing of complex shapes beyond the capability of most other 3D printing types. However, the high temperatures required for the sintering can lead to considerably longer cooling times.

Materials used range from nylon, ceramics, and glass to metals such as steel, aluminum, and silver. They produce durable goods, well-suited for functional testing (hence their popularity with start-ups), more robust than those made by SLA but with a rougher finish.

Selective laser sintering is ideal for custom manufacturing, end-use parts, and functional prototyping.

3. FUSED DEPOSITION MODELING (FDM)

Fused deposition modeling (FDM) (also known as fuse filament fabrication: FFF) is the 3D printing type used in household desktop 3D printers - even 3D pens - and is the most popular at the consumer level.

An FDM printer extrudes thermoplastic filaments through a heated nozzle layer-by-layer onto your build platform. It provides a quick and cost-effective way to make basic proof-of-concept models, along with low-cost prototypes of simple parts. It can be used for functional testing in some instances. Still, the relative lack of strength limits it, as well as the surface finishes' roughness (though higher-quality finishes are achievable via chemical and mechanical polishing).

As well as thermoplastics, a printer can also extrude a range of support materials, the most common being PLA (polylactic acid plastic) and ABS (acrylonitrile butadiene styrene).

Although the process is relatively similar to stereolithography, it has a lower resolution than both it and SLS, so it is ill-suited for projects requiring more complex designs or parts. Industrial FDM’s use soluble supports to help mitigate these risks, but it comes at a hefty price. 

FDM also has a slower printing speed than SLA, the overall time being dependent on the size and complexity of the project.

The mechanical strength and heat resistance make it a natural choice for the production of functional prototypes. However, it is popular with industries as diverse as food producers, automobile manufacturers, and the medical sector!

Fused deposition modeling is ideal for the more basic proof-of-concept modeling and simpler prototypes.

4. DIGITAL LIGHT PROCESS (DLP)

Digital Light Processing is similar to SLA in the respect that it cures liquid resin using light. While SLA does this with a UV laser, DLP uses a more conventional light source- such as an arc lamp- with an LCD panel. The resin hardens when exposed to the light, and it’s all applied in a single pass, making it a much faster option.

Like SLA, DLP produces parts that boost accuracy and superb resolution, but it also suffers from the need for support structures and post-curing. With only a shallow vat of resin required, however, the process benefits from less wastage and lower running costs. The printing speed is the real kicker though - each layer is produced in a matter of seconds.

Although it’s often used for rapid prototyping, the faster rate of production also lends itself to lower-volume runs of plastic parts.

Digital light processing is ideal for fast prototypes and unorthodox, organic shapes.

5. MULTI-JET FUSION

Like SLS, Multi Jet Fusion also uses nylon powder to build functional parts. However, instead of the laser, SLS uses to sinter (or fuse) the powder, it uses multiple inkjet heads to apply fusing agents to the bed of nylon powder. The heating element is then passed over the bed, fusing the layers together. The powder bed and the printed parts are then removed to a separate processing station where any unfused powder can be hoovered, ready to be reused.

This feature - along with the accelerated build time - gives it the benefit of lower production costs, while the production technique delivers a smoother surface finish than SLS. 

6. POLYJET 

This is another plastic 3D process, but with a twist - it can produce parts with multiple properties (i.e. different colors and materials). This gives designers the ability to prototype elastomeric or over-molded parts. SLS is the more prudent option for single, rigid plastics. Still, the over molding options Polyjet gives you can speed up your iteration and validation process and can be a huge cost-saver.

7. DIRECT METAL LASER SINTERING (DMLS) 

Direct Metal Laser Sintering’s main selling point is that it opens up the possibility of metal part design. It is used most often to reduce metal, multi-part assemblies into a single component or lightweight parts with internal channels or hollowed-out features. 

This provides a viable option for not only prototyping but the production itself, as the parts produced boast the same density as those made by traditional metal casting. The complex geometries can make it a valuable option for medical applications, where the design needs to mimic an organic structure.

8. ELECTRON BEAM MELTING (EBM)

Electron Beam Melting is another metal printing method, similar to DMLS, in that the parts are formed from metal powder. The main difference between the pair is the heat source- whereas DMLS uses a laser; as the name suggests, EBM uses an electron beam to induce the fusion between the metal particles.

Here, a focused electron beam scans across a thin layer of powder, causing localized melting and then solidification, built up to create the finished (solid) product.

Another difference is the necessity for EDM to be carried out under vacuum conditions; therefore, the process can only be used for conductive materials.

It is, however, capable of producing fully-dense parts in a selection of metal alloys, up to medical grade, as this has led to its popularity for a range of applications in that industry, notably for implants. Other hi-tech sectors like aerospace have followed suit and begun testing the capabilities of EBM for its manufacturing requirements.

EBM has a generally faster build speed than DMLS due to its higher energy density, although its minimum feature sizes are typically larger.

The Most Common Materials Used

There have been giant strides taken with the range of materials now used in production with 3D printing and in a selection of different states: powder, pellets, filament, and resin, to name a few).

Now specific materials are even being developed for dedicated uses as they open up the possibilities of the technology. We need a whole other article to go through them properly, but here are the main ones:

1. Plastics 

Polyamide (or nylon) is a solid yet flexible plastic material that has gained popularity in 3D printing, used in powder form with the sintering process and filament with fused deposition (FDM). When powdered, it can be combined with (powdered) aluminum to create aluminide, another popular sintering option.

ABS is a common plastic whose impressive strength, and range of colors, have seen it become a popular choice (in filament form) with entry-level machines.

Laywood has developed especially for 3D printing and found its application predominantly with entry-level machinery. It is also in filament form, a composite of wood and polymer.

PLA’s biodegradability has been a critical factor as it has gained traction in the market, used in resin for DLP/SL and filament for FDM. 

2. Metals 

Aluminum and cobalt derivatives are two of the most common of a growing number of metals (and metal composites) being used for industrial-grade 3D printing.

Titanium has also been used for some time, in powder form with sintering, melting, and EBM.

Stainless Steel’s strength made it an obvious choice, used in powdered form for sintering, melting, and EBM too. 

In the last few years, gold and silver have been added to this list, with obvious potential implications in the jewelry industry.

3. Others 

Ceramics are a relative newcomer to the list, though as yet, without the unqualified success of plastics and metals.

Ireland-based Mcor Technologies Ltd pioneered paper-based 3D technology, although they have since been liquidated and taken over CleanGreen3d Ltd, so it remains to be seen if they can further the progress made here.

Exciting developments with biomaterials - including living tissue (yes, you read that right) - could have potentially game-changing potential for healthcare. Imagine being able to print human organs for transplant! This is one aspect in particular that feels very much in the realm of science-fiction. Or, at least it did.

Biomaterials could also be used for foodstuffs, again with a potentially seismic impact on the industry and the environment. 

Chocolate has been the first adoption with other foodstuffs, but developments continue with the goal of producing finely-balanced whole meals. 

 

You can also check our article on A Beginner's Guide to 3D Printing | How Does a 3D Printer Work?

What Are the Most Common Applications? 

The origins of 3D printing were built on its uses in rapid industrial prototyping, but innovations made with machinery, materials, and software have served to smash open a host of other markets. 

The medical industry was an early adopter, quick to see the potential the technologies customization offered.

Aerospace and automobiles were also quick to get on board, seeing the opportunities there with their manufacturing processes. 

Jewelry, art, fashion, food, and the market for consumer 3D printing are the next industries deep in development and on the cusp of their commercial breakthrough.

As you can see, 3D printing is a fascinating and ever-evolving technology. There are so many possibilities for creativity and innovation in this field that we’ve barely scratched the surface. In fact, it will be decades before we even know where the surface truly is! 

We hope you found our blog post about what 3D printing is useful. To learn more about how your company can use it, visit our website at 3djunkies.com or email our customer service team at support@3djunkies.com.