Types of 3D Printing Technology

Understanding various types of 3D printing technologies available for rapid prototyping and part production.

The term 3D printing encompasses several manufacturing techniques for building parts layer by layer. Each method for forming plastic and metal parts varies, with differences in material selection, surface finish, durability, manufacturing speed, and cost.

There are several types of 3D printing include:

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)

Choosing the right 3D printing method for your product requires understanding the strengths and weaknesses of each process and mapping these attributes to your product development needs. Let's first discuss how 3D printing fits into the product development cycle and then explore common types of 3D printing technologies and their respective advantages.

3D Printing for Rapid Prototyping and Beyond

It can be stated with certainty that 3D printing is most commonly used for prototyping. It enables the rapid production of individual parts, allowing product developers to validate designs in a cost-effective manner. Identifying the purpose of the prototype will help determine which 3D printing technology is most suitable. Additive manufacturing can be applied to a range of prototypes, from simple physical models to parts used for functional testing.

While 3D printing is synonymous with rapid prototyping, it can also be a viable manufacturing method in certain cases. It is typically applied to low volumes and complex geometries. Components for aerospace and medical applications are often ideal candidates for 3D printing production as they frequently meet the criteria described earlier.

Five 3D Printing Considerations

Just like most things in life, there are rarely simple answers when it comes to choosing a 3D printing method. When assisting clients in evaluating their 3D printing options, we typically highlight five key criteria to determine which technology can meet their needs:

Budget

Mechanical requirements

Cosmetic appearance

Material selection

Geometry

Let's outline some common plastic 3D printing methods and discuss when each method can provide maximum value for product developers, engineers, and designers.

Stereolithography (SLA)

Stereolithography (SLA) is one of the earliest industrial 3D printing processes. SLA printers excel at producing parts with high levels of detail, smooth surface finish, and tight tolerances. The high-quality surface finish of SLA parts not only looks good but also contributes to the functionality of the parts—such as testing component fit. It finds extensive use in the medical industry, with common applications including anatomical models and microfluidics. We utilize SLA printers from 3D Systems, including Vipers, ProJets, and iPros, to produce SLA parts.

Selective Laser Sintering

Selective Laser Sintering (SLS) melts nylon-based powder into solid plastic. Since SLS parts are made from genuine thermoplastic materials, they are durable, suitable for functional testing, and can support moving hinges and snap fits. Compared to SLA, parts are stronger but have a rougher surface finish. SLS does not require support structures, allowing the entire build platform to be used for nesting multiple parts within one build, making it suitable for higher part quantities than other 3D printing processes. Many SLS parts are used for prototype designs that will eventually be injection molded. For our SLS printers, we utilize the sPro140 machine developed by 3D Systems.

PolyJet

PolyJet is another plastic 3D printing process but with a twist. It can manufacture parts with various properties such as color and materials. Designers can leverage this technology for prototyping elastomeric or overmolded parts. If your design is a single rigid plastic, we recommend sticking to SL or SLS—it's more cost-effective. However, if you're prototyping overmolded or silicone rubber designs, PolyJet allows you to avoid investing in tools early in the development cycle. This can help you iterate and validate your designs faster and save you money.

Digital Light Processing (DLP)

Digital Light Processing is similar to SLA in that it uses light to cure liquid resin. The main difference between these two technologies is that DLP uses a digital light projection screen, whereas SLA uses ultraviolet lasers. This means DLP 3D printers can image the entire layer of the build at once, increasing build speed. While commonly used for rapid prototyping, the higher throughput of DLP printing makes it suitable for low-volume production of plastic parts.

Multi-Jet Fusion

Similar to SLS, Multi-Jet Fusion (MJF) utilizes nylon powder to manufacture functional parts. Instead of using laser sintering powder, MJF applies a fusing agent to the nylon powder bed using an array of inkjets. Subsequently, a heating element passes over the bed to melt each layer. This results in more consistent mechanical properties and improved surface finish compared to SLS. Another benefit of the MJF process is accelerated production times, thereby reducing manufacturing costs.

Fused Deposition Modeling (FDM)

Fused Deposition Modeling (FDM) is a common desktop 3D printing technology used for plastic parts. FDM printers extrude plastic filament layer by layer onto a build platform. It's a cost-effective method for quickly producing physical models. In some cases, FDM can be used for functional testing, but the technology is limited by relatively rough surface finish and lack of strength in parts.

Metal 3D Printing Processes

Direct Metal Laser Sintering (DMLS)

Metal 3D printing opens up new possibilities for the design of metal parts. The process for 3D printing metal parts that we use at Protolabs is Direct Metal Laser Sintering (DMLS). It's commonly used to consolidate metal, multi-component assemblies into single parts or lightweight parts with internal channels or hollow features. DMLS is viable for both prototype design and production, as the part density is as high as parts produced using traditional metal manufacturing methods like machining or casting. Creating metal parts with complex geometries also makes it suitable for medical applications where parts must mimic organic structures.

Electron Beam Melting

Electron Beam Melting is another metal 3D printing technology that uses an electron beam controlled by electromagnetic coils to melt metal powder. The printing bed is heated and kept under vacuum conditions during the manufacturing process. The temperature to which the material is heated depends on the material being used.

When to Use 3D Printing

As mentioned earlier, several common denominators exist in 3D printing applications. If your part quantity is relatively low, 3D printing might be optimal—our guidance for 3D printing service customers typically ranges from 1 to 50 parts. As volumes approach hundreds, it becomes necessary to explore other manufacturing processes. If your design features complex geometries critical to part functionality, such as aluminum parts with internal cooling channels, then 3D printing might be your only option.

Ultimately, choosing the right process involves aligning the advantages and limitations of each technology with the most critical requirements of the application. In the early stages, when ideas are being thrown around, and you just need a model to share with colleagues, you don't need to worry too much about those stair-step surface finishes. But once you reach the stage where user testing is needed, factors like cosmetics and durability start to become important. While there's no one-size-fits-all solution, leveraging 3D printing technology correctly throughout the product development process will reduce design risks and ultimately result in better products.