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Your Guide to Additive Manufacturing: Part I

Companies across all industries from automotive to aerospace to consumer products and even architecture misunderstand how many 3D printing technologies there are and which applications each should be used for.

While companies across all industries from automotive to aerospace to consumer products and even architecture misunderstand how many 3D printing technologies there are and which applications each should be used for, what is even more striking is how often an engineer, designer, or architect knows a great deal about the specific additive technology they use but know little about the benefits of the other additive processes.

The engineer specializing in combustion technology knows chapter and verse about DMLS but little about SLA. The FDM user assumes you can’t get true flexible 3D printed parts because they only print hard thermoplastics. Adding to the confusion, are all the different lists of 3D printing types that don’t match up. And how many types are there?

To provide clarification, this is the first part in a series that will review each Additive Manufacturing technology as defined by ASTM/ISO 52900; examine the situations in which these technologies work well and don't work well; and look at the design distinctions between them.

In the coming series of articles, we’ll not only review the additive manufacturing technologies and their corresponding materials but also what design criteria and post-processing requirements you need to be aware of when working with them. Here is a quick review of the seven categories as defined by the ASTM with more to follow on each in the coming months.

Binder Jetting

Originally developed at MIT and patented in 1993, Binder Jetting “is an additive manufacturing process in which a liquid bonding agent is selectively deposited to join powder materials.” Binder Jetting is the only additive process that does not require heat. The equivalent of a “print head,” not unlike what you would see on a traditional paper printer, only instead of dispensing ink it dispenses an adhesive material that precisely binds together the filament particles into the desired part. Not known for strong parts, today’s Binder Jetting machines can produce extraordinarily detailed parts with an amazing variety of colors.

Directed Energy Deposition

Directed Energy Deposition (DED) “is an additive manufacturing process in which focused thermal energy is used to fuse materials by melting as they are being deposited.” This is a perfect example of the confusion that surrounds the whole additive space. You can find websites that define DED as an umbrella term encompassing all metal 3D printing technologies, including DMLS or EBM, but that is wrong. Directed Energy Deposition doesn’t use a powder bed system. A laser fuses the metal filament from a wire spool or, in some cases, powder being deposited by a nozzle but only in the specific area where there should be a part. This is a different approach than the more commonly known metal processes. Commonly known DED processes include WAAM (Wire Arc Additive Manufacturing), LMD (Laser Metal Deposition), and LENS (Laser Engineered Net Shaping). In the article on Directed Energy Deposition, we will discuss the pros and cons of each.

Material Extrusion

Our old standby known simply as FDM (Fused Deposition Modeling) or, less often, FFF (Fused Filament Fabrication). Material Extrusion “is an additive manufacturing process in which material is selectively dispensed through a nozzle or orifice.” First patented in the 1980s by Scott Crump and originally licensed to Stratasys, FDM is easily the most widespread of the Additive technologies, FDM printers are the easiest to get up and running and have the most cost-effective consumables. The process is so well known what are we going to say about it? In the months ahead we’ll look at how the FDM landscape has changed and what we can expect in new materials in the years ahead.

Material Jetting

Developed in Israel in the late nineties, Material Jetting “is an additive manufacturing process in which droplets of a build material are selectively deposited.” Far more commonly known by it’s patented trade name PolyJet, Material Jetting is the fastest of the additive technologies while also producing parts of incredible detail, multi-material, and color variety. Material Jetted parts are not known for strength or long-lasting durability but for quick prototypes and proof of concept, a great technology we’ll be discussing in more detail.

Powder Bed Fusion

An umbrella term for several different 3D printing processes, Powder bed fusion “is an additive manufacturing process in which thermal energy selectively fuses a region of powder bed.” This includes but is not limited to SLS (Select Laser Sintering), SLM (Select Laser Melting), and EBM (Electron Beam Melting). PBF works with metals and polymers and has a wide variety of considerations from when to use support structures and what post-processing is required. Perhaps the most widely used 3D Printing process after FDM, we’ll be getting into this much greater detail.

Sheet Lamination

An interesting hybrid technology made well-known by the former Irish company Mcor, Sheet Lamination is an additive manufacturing process in which sheets of material are bonded to form a part. While Sheet Lamination is widely known for using paper to make objects, the technology itself is compatible with sheets of metal and plastic. Perhaps the least known of the additive technologies, we’ll look at the pros and cons of this approach in a later article and assess where it is today.

Vat Photopolymerization

Commonly thought of as synonymous with SLA, Vat Photopolymerization is a category of 3D printing using “a process in which liquid polymer in a vat is selectively cured by light-activated polymerization.” Although similar to Material Jetting in that they both use cured resins to produce parts, Vat Photopolymerization is a very different process that includes SLA (Stereo Lithography), DLP (Digital Light Processing), and DLS from Carbon (Digital Light Synthesis).  This technology seems to keep reinventing itself as with the 3D printed composite diamonds from Sandvik in Sweden using their SLA process. A later article will examine the different types, what they can do, and where they are headed in the future.

Join us in the coming months as we provide clarity on the different additive manufacturing technologies to help you determine which best fits your needs.

The big takeaway is not that there is one right overall additive process. The big takeaway from this series is that there is no all-encompassing 3D printing technology that is right for every application. All decisions are driven by the performance needs of the printed part. Are there engineering requirements such as tensile strength and load factors that dictate material property requirements? Once you determine the material properties needed, focus on which additive technologies work with those materials and which don’t.

Jack Heslin is a freelance contributor to Design News on additive manufacturing topics. He has been a regular speaker and moderator at industry trade shows including MDM East, MDM West, and ADM Toronto. His work in 3D printing includes being the first Enterprise Executive hire at MakerBot, and Director of Business Development for Lazarus3D. He is currently a Regional Account Manager for Stratasys Direct Manufacturing supporting New York and Connecticut.



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