Types of 3D Printing Technology

Despite 3D printing being nearly synonymous with rapid prototyping, there are scenarios when it’s a viable production process. Typically these applications involve low-volumes and complex geometries. Often, components for aerospace and medical applications are ideal candidates for production 3D printing as they frequently match the criteria previously described.

Five 3D Printing Considerations

Like most things in life, there’s rarely a simple answer when selecting a 3D printing process. When we assist customers evaluating their 3D printing options, we typically point to five key criteria to determine what technology will meet their needs:

1. Budget
2. Mechanical requirements
3. Cosmetic appearance
4. Material selection
5. Geometry

Polymer 3D Printing Processes

Let’s outline some common plastic 3D printing processes and discuss when each provides the most value to product developers, engineers, and designers.

Stereolithography (SLA)

Stereolithography (SLA) is the original industrial 3D printing process. SLA printers excel at producing parts with high levels of detail, smooth surface finishes, and tight tolerances. The quality surface finishes on SLA parts, not only look nice, but can aid in the part’s function—testing the fit of an assembly, for example. It’s widely used in the medical industry and common applications include anatomical models and microfluidics.  We use Vipers, ProJets, and iPros 3D printers manufactured by 3D Systems for SLA parts.

Selective Laser Sintering (SLS)

Selective laser sintering (SLS) melts together nylon-based powders into solid plastic. Since SLS parts are made from real thermoplastic material, they are durable, suitable for functional testing, and can support living hinges and snap-fits. In comparison to SL, parts are stronger, but have rougher surface finishes. SLS doesn’t require support structures so the whole build platform can be utilised to nest multiple parts into a single build—making it suitable for part quantities higher than other 3D printing processes. Many SLS parts are used to prototype designs that will one day be injection-moulded. For our SLS printers, we use sPro140 machines developed by 3D systems.

PolyJet

PolyJet is another plastic 3D printing process, but there’s a twist. It can fabricate parts with multiple properties such as colours and materials. Designers can leverage the technology for prototyping elastomeric or overmoulded parts. If your design is a single, rigid plastic, we recommend sticking with SL or SLS—it’s more economical. But if you’re prototyping an overmoulding or silicone rubber design, PolyJet can save you from the need to invest in tooling early in the development cycle. This can help you iterate and validate your design faster and save you money.

Digital Light Processing (DLP)

Digital light processing is similar to SLA in that it cures liquid resin using light. The primary difference between the two technologies is that DLP uses a digital light projector screen whereas SLA uses a UV laser. This means DLP 3D printers can image an entire layer of the build all at once, resulting in faster build speeds. While frequently used for rapid prototyping, the higher throughput of DLP printing makes it suitable for low-volume production runs of plastic parts.

Multi Jet Fusion (MJF)

Similar to SLS, Multi Jet Fusion also builds functional parts from nylon powder. Rather than using a laser to sinter the powder, MJF uses an inkjet array to apply fusing agents to the bed of nylon powder. Then a heating element passes over the bed to fuse each layer. This results in more consistent mechanical properties compared to SLS as well as improved surface finish. Another benefit of the MJF process is the accelerated build time, which leads to lower production costs.

Fused Deposition Modelling (FDM)

Fused deposition modelling (FDM) is a common desktop 3D printing technology for plastic parts. An FDM printer functions by extruding a plastic filament layer-by-layer onto the build platform. It’s a cost-effective and quick method for producing physical models. There are some instances when FDM can be used for functional testing but the technology is limited due to parts having relatively rough surface finishes and lacking strength.

Metal 3D Printing Processes

Direct Metal Laser Sintering (DMLS)

Metal 3D printing opens up new possibilities for metal part design. The process we use at Protolabs to 3D print metal parts is direct metal laser sintering (DMLS). It’s often used to reduce metal, multi-part assemblies into a single component or lightweight parts with internal channels or hollowed out features. DMLS is viable for both prototyping and production since parts are as dense as those produced with traditional metal manufacturing methods like machining or casting. Creating metal components with complex geometries also makes it suitable for medical applications where a part design must mimic an organic structure.

Electron Beam Melting (EBM)

Electron beam melting is another metal 3D printing technology that uses an electron beam that's controlled by electromagnetic coils to melt the metal powder. The printing bed is heated up and in vacuum conditions during the build. The temperature that the material is heated to is determined by the material in use. 

When to Use 3D Printing

As stated earlier, there are a couple common denominators among 3D printing applications. If your part quantities are relatively low, 3D printing can be optimal—the guidance we give our 3D printing service customers is usually 1 to 50 parts. As volumes start to near the hundreds, it’s worth exploring other manufacturing processes. If your design features complex geometry that is critical to your part’s function, like an aluminium component with an internal cooling channel, 3D printing might be your only option.

Selecting the right process comes down to aligning the advantages and limitations of each technology to your application’s most important requirements. In the early stages when ideas are being thrown around and all you need is a model to share with a colleague, those stair-stepping surface finishes on your part aren’t of much concern. But once you hit the point where you need to conduct user testing, factors like cosmetics and durability start to matter. Although there is no one-size-fits-all solution, properly utilising 3D printing technology throughout product development will reduce design risk and, ultimately, result in better products.