3D printing is used for rapid prototyping, building concept models, making one-off functional devices, and even low volume production. The reason it is so versatile is that 3D printing can directly translate a 3D digital model into a physical object in very few steps. A 3D printer processes instructions from software that “slices” the model into individual layers. These slices of data dictate how the printer should deposit or fuse material on each layer to build objects one thin cross-section at a time.
3D printing methods and processes are not all the same. The term 3D printing covers a family of different manufacturing technologies and each one has its strengths and trade-offs. This article will go into detail on how to get the most out of different 3D printing services and navigate different process selections.
What are the Different 3D Printing Processes?
Industrial 3D printing, or additive manufacturing, technologies have the advantage of providing quality parts consistently and with high output. Because of the investment needed to run this equipment, most access to industrial additive manufacturing is through a 3D printing service or marketplace. Some of the core methods used to make plastic 3D prints using a service are SLS, MJF, SLA, FDM, and DLS™. These processes are briefly described below.
Common Industrial 3D Printing Service Options - Plastic Part Production
From left: SLS, HP MJF, SLA, FDM and DLS.
Selective Laser Sintering (SLS) is a laser powder bed fusion process (LPBF) where a fine layer of nylon powder is spread across a heated chamber and a laser will fuse cross-sections of the part. SLS can build parts economically in bulk without the need for support structures.
HP Multi Jet Fusion (HP MJF) selectively fuses cross-sections of parts in a plastic powder bed using a combination of ink-jetted fusion and detail agents with the addition of heat. Like SLS, HP MJF can build parts economically in bulk without supports. MJF has a slightly higher output than SLS in production settings.
Stereolithography (SLA) parts are formed by an ultraviolet (UV) light selectively curing cross-section profiles, layer-by-layer, from the bottom to the top. SLA resins can exhibit a variety of properties and typically have superior detail and surface finish compared to other 3D printing processes.
Fused Deposition Modeling (FDM) uses a reel of a thermoplastic material that is fed into a heated extruder where it is deposited by a nozzle to form parts. FDM has a very high variety of plastic and color choices as well as the largest build area compared to other plastic 3D processes.
Carbon Digital Light Synthesis™ (DLS™) prints continuously to make parts with isotropic features using a DLP projector to cure a part in a liquid resin. Parts then go through secondary thermal cycles to activate engineered traits. DLS™ parts are a good blend of end-use properties and cosmetic feature details.
Which 3D Printing Process Should You Choose?
Each unique additive manufacturing process can complement requirements ranging from prototyping to production of parts. General-purpose tools, such as SLS, HP MJF, and FDM, can be used for high-iteration prototyping and even some pre-production manufacturing due to their versatility. However, those processes may have too coarse of a surface for cosmetic needs where processes like SLA may be more beneficial.
SLA prototyping is a powerful tool for validating designs before moving to scaled production using injection molding. Bridging the gap between prototype and production, Carbon DLS™ 3D printing can achieve end-use mechanical properties, mold-like finishes, and the ability to scale into high quantities for smaller components. The infographic below showcases some of the deciding factors to help narrow which 3D printing process to select depending on project needs.
Infographic Courtesy of Xometry.
For example, if your intention is to prototype a clear housing for a product demonstration then SLA may be the best bet because it can make an aesthetic part with translucent materials. A great example is SLA Accura ClearVue with a QuickClear finish. In contrast, if a part has end use functional requirements and multiple snap feature that need to be resistant to fatigue, then SLA would not be the best choice and options like SLS, HP MJF, and Carbon DLS™ would be more favorable processes.
Sometimes the size of the part to be produced is one of the biggest constraints. 3D printing processes have different size limitations. Most processes can build parts under 9”, but very few can build parts over 24”--which often makes FDM the best choice for large format 3D printing. 3D printers can provide solutions to many aspects of product development and even offer an end means of production. It is important to consider both the process and the 3D model to best utilize the multitude of options available through services.
How to Prepare a Part for 3D Printing
3D printing is the process of forming an object by depositing or fusing the material together through the guidance of a 3D model. A 3D CAD file is necessary for all 3D printing methods. File selection and preparation can help ensure the best results from printing services.
Although many 3D printing services can use a multitude of CAD formats, 3D printing software requires a mesh file such as an STL format. Mesh formats are the digital equivalent of a balloon, being made of facet-like features forming the outer shell of a part. The inside of a part is defined by these features but in a digital sense, the body is not considered solid. This can lead to STL files being easily corrupted by missing part of the mesh outer skin, making the file non-watertight. Sometimes repairs of STL files can accidentally create unwanted features. It is recommended, if possible, to provide another file type that is a solid CAD body, such as STP or Parasolid.
Many 3D printing service bureaus can directly support native CAD exports from popular 3D modeling software.
Solid CAD bodies provide more than just boundary information, but also have geometrical information like scale and feature topology. Most 3D printing service bureaus and operators have a method of converting solid CAD to STL before processing. By providing a solid CAD body versus a mesh format, the operator can do any necessary repairs and not have questions on the intended units of the 3D model. An added benefit is the service technicians can create a mesh from the solid file at an appropriate resolution for the given process. Some of the most common solid model formats used are .stp, .step, .sldprt, .x_t, .x_b, .ipt, and .prt.
Xometry’s On-Demand 3D Printing
Manufacturing services like Xometry add significant value through instant online quoting from 3D files over a variety of industrial additive processes. This, combined with specific 3D printing design guides and on-staff experts can lead to parts that meet or exceed project requirements. You can try out Xometry’s Instant Quoting Engine™ here and get instant quotes on CNC machining, 3D printing, injection molding, sheet metal fabrication, urethane casting, and more.
