The term 3D printing encompasses several manufacturing technologies that build parts layer-by-layer. Each vary in the way they form plastic and metal parts and can differ in material selection, surface finish, durability, and manufacturing speed and cost. There are several types of 3D printing, which include:
Stereo lithography (SLA)
Selective Laser Sintering (SLS)
Fused Deposition Modeling (FDM)
Digital Light Process (DLP)
Multi Jet Fusion (MJF)
PolyJet
Sintering by direct metal laser (DMLS) Electron Beam Melting (EBM)
Selecting the right 3D printing process for your application requires an understanding of each process’ strengths and weaknesses and mapping those attributes to your product development needs. First, let’s talk about how 3D printing fits into the product development cycle. Next, let’s look at the most common 3D printing technologies and the benefits of each one. 3D Printing for Rapid Prototyping and Beyond
Prototyping is probably the most common application for 3D printing. Its ability to quickly manufacture a single part enables product developers to validate and share ideas in a cost-effective manner. Determining the purpose of your prototype will inform which 3D printing technology will be the most beneficial. Additive manufacturing can be suitable for a range of prototypes that span from simple physical models to parts used for functional testing.
Stereo lithography is one type of 3d printing
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
When choosing a 3D printing method, there is rarely a straightforward answer, just like there is with most things in life. When we assist customers evaluating their 3D printing options, we typically point to five key criteria to determine what technology will meet their needs:
Budget
Needs for mechanical systems Cosmetic appearance
Material selection
Geometry
SLS parts post-processing
Methods for 3D Printing Polymer Let’s outline some common plastic 3D printing processes and discuss when each provides the most value to product developers, engineers, and designers.
Stereo lithography (SLA)
SLA, or stereo lithography, was the first industrial 3D printing method. SLA printers excel at producing parts with high levels of detail, smooth surface finishes, and tight tolerances. Quality surface finishes on SLA parts not only make them look good, but they can also help the part do its job, like testing an assembly’s fit. It’s widely used in the medical industry and common applications include anatomical models and micron.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. Parts are stronger than SL, but their surface finishes are rougher. SLS doesn’t require support structures so the whole build platform can be utilized to nest multiple parts into a single build—making it suitable for part quantities higher than other 3D printing processes. A lot of SLS components are used to test designs that will eventually be injected molded. 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 colors and materials. Designers can leverage the technology for prototyping elastomeric or over molded parts. If your design is a single, rigid plastic, we recommend sticking with SL or SLS—it’s more economical. PolyJet, on the other hand, can help you avoid spending money on tooling early on in the development process if you’re prototyping a silicone rubber or over molding design. This can help you iterate and validate your design faster and save you money.
Processing Digital Light (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. Because of this, DLP 3D printers can simultaneously image every layer of the build, 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.
Fusion of several jets (MJF) Multi Jet Fusion, like SLS, uses nylon powder to build functional parts. MJF applies fusing agents to the bed of nylon powder with an inkjet array rather than a laser to sinter the powder. Then a heating element passes over the bed to fuse each layer. When compared to SLS, this results in improved surface finish and mechanical properties that are more consistent. Another benefit of the MJF process is the accelerated build time, which leads to lower production costs.
Modeling of Fused Deposition (FDM) A common desktop 3D printing technology for plastic parts is fused deposition modeling (FDM). 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. FDM can be used for functional testing in some cases, but the technology is limited because parts have surface finishes that are relatively rough and lack strength. Metal 3D Printing Processes
Sintering by direct metal laser (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. 3D printing can be a great option if you need to make a small number of parts. Our recommendations for our customers who use our 3D printing service typically range from one to fifty 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 aluminum component with an internal cooling channel, 3D printing might be your only option.
Aligning the benefits and drawbacks of each technology with the most crucial requirements of your application is the key to selecting the appropriate process. Those stair-stepping surface finishes on your part aren’t very important in the early stages, when ideas are being discussed and all you need is a model to show a coworker. 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 utilizing 3D printing technology throughout product development will reduce design risk and, ultimately, result in better products.
