In the realm of manufacturing, there's a revolution underway. Additive manufacturing (AM), often synonymous with 3D printing, is redefining how products are designed, prototyped, and even mass-produced. Instead of traditional subtractive methods where material is removed to achieve the final product, AM adds material layer by layer, bringing intricate designs to life with precision and flexibility. As AM technologies advance, they're reshaping industries, from healthcare to aerospace, offering new possibilities previously deemed impossible.
In this overview, we'll delve briefly into the seven primary AM technologies recognized by ISO and ASTM standards, exploring their sub-technologies, advantages, drawbacks, complementary processes and common applications. Some new AM technologies that do not necessarily fit into these seven categories will also be considered.
With time, we are going review individual technologies in detail and share the links of each review here. Let’s start-
1. VAT Photopolymerization
VAT Photopolymerization is an AM technique that involves the use of a vat/container filled with a liquid photopolymer resin. A UV light source—either a laser or projector—illuminates specific areas of the resin, causing it to solidify layer by layer. As each layer solidifies, the build platform moves, allowing the next layer to be cured on top. This process continues until the entire part is completed. Due to its ability to produce fine details and complex geometries, it's especially favored for applications requiring high surface finish and intricate designs.
Typical Pre-Processes: CAD design, slicing/build preparation, resin selection, support structure generation.
Typical Post-Processes: Support removal, UV post-curing, debindering and sintering (LMM and LCM), surface finishing.
Common Uses: Jewelry, dental molds.
Most Relevant Industries: Dental, jewelry, healthcare, automotive, consumer goods.
Pros: High detail, smooth finishes.
Cons: Brittle materials, limited build volume.
2. Material Extrusion
Material Extrusion is the most common AM method. Here a material, typically in filament form, is heated and extruded through a nozzle, deposited layer by layer onto a build platform. The nozzle moves in predefined paths based on the 3D model, depositing material that solidifies upon cooling. This is one of the most common AM techniques due to its simplicity, accessibility, and wide range of usable materials, from thermoplastics to composites and even certain metals.
Typical Pre-Processes: CAD design, slicing/build preparation, filament selection, support structure generation.
Typical Post-Processes: Support removal, surface finishing, (For metal FDM): washing the green part, debinding, sintering.
Common Uses: Prototyping, functional parts, jigs and fixtures, educational projects.
Most Relevant Industries: Healthcare, manufacturing, electronics, education, construction.
Pros: Cost-effective, wide material range.
Cons: Limited resolution, slower production.
3. Powder Bed Fusion
Powder Bed Fusion (PBF) encompasses AM techniques that involve spreading a thin layer of powder material over a build platform. A heat source, like a laser or electron beam, selectively fuses or sinters regions of the powder bed based on the design. If a laser is used to sinter or melt the material, the technology is referred to as Laser Powder Bed Fusion (L-PBF). Once a layer is fused, the build platform descends, a new layer of powder is spread, and the process repeats. PBF can produce parts with high mechanical strength and is suitable for both prototyping and functional end-use parts, especially when metal alloys are used.
Typical Pre-Processes: CAD design, slicing/build preparation, powder selection, build platform preparation
Typical Post-Processes: Part removal, support removal, heat treatment, surface finishing, infiltration (for some materials).
Common Uses: Powder bed has a wide range of applications.
Most Relevant Industries: Medical, aerospace, automotive, energy, defense.
Pros: Wide material range, complex structures.
Cons: High cost, post-treatments often required.
4. Binder Jetting
Binder Jetting is an AM method where a liquid binding agent is selectively deposited onto a powder bed to join the powder particles. After each layer of binder is applied, a new layer of powder is spread on top, and the process repeats until the part is completed. After printing, the "green" part undergoes post-processing steps like sintering or infiltration to enhance its mechanical properties. This technique is versatile and can be employed with a variety of materials, from metals to ceramics to sand.
Typical Pre-Processes: CAD design, slicing/build preparation, powder selection, binder cartridge preparation.
Typical Post-Processes: De-powdering, infiltration, debinding and sintering, surface finishing.
Common Uses: Decorative items, prototypes, molds.
Most Relevant Industries: Art, architecture, automotive, foundry, aerospace.
Pros: Suitable for full-color printing, scalable, no support structures.
Cons: Lower strength, requires post-processing for enhanced properties.
5. Directed Energy Deposition
In Directed Energy Deposition (DED), material is continuously fed into a melt pool created by a focused thermal energy source, such as a laser, electron beam, or arc. The material, often in powder or wire form, is melted and deposited layer by layer, with the nozzle moving along a specified path. DED is versatile, capable of producing large-scale parts, and is especially useful for repairing or adding material to existing components.
Typical Pre-Processes: CAD design, slicing/build preparation, feedstock selection, substrate preparation.
Typical Post-Processes: Heat treatment, surface machining, part removal.
Common Uses: Turbine blade repair, large tooling, large functional parts.
Most Relevant Industries: Aerospace, defense, marine, energy, automotive.
Pros: Suitable for repairs, large-scale components, multi-material parts.
Cons: Rougher surface finish, less precision compared to powder bed fusion.
6. Material Jetting
Material Jetting operates somewhat similarly to inkjet printing. Droplets of build material are precisely jetted or deposited onto a build surface, where they solidify. This method often uses UV light or another external agent to solidify the jetted material. Because of its high precision, it's capable of producing parts with intricate details, smooth surfaces, and complex geometries, often in full color or with multiple materials.
Typical Pre-Processes: CAD design, slicing/build preparation, material cartridge setup, platform calibration.
Typical Post-Processes: Support removal, UV post-curing, surface finishing.
Common Uses: Prototypes, complex geometries, short-run production.
Most Relevant Industries: Medical, dental, consumer products, electronics, automotive.
Pros: High detail, multi-material capability, full-color models.
Cons: Limited material range, expensive.
7. Sheet Lamination
Sheet Lamination, the least used AM technology, involves the bonding of sheets of material together, layer by layer, using either adhesive or some form of external force or heat. After each sheet is bonded, the desired cross-sectional shape is often achieved using a cutting method, such as a laser or knife. This technique offers a unique approach to AM, allowing for the creation of large parts and the use of materials that might not be suitable for other AM processes.
Typical Pre-Processes: CAD design, slicing/build preparation, material sheet preparation, adhesive application (if needed).
Typical Post-Processes: Excess material removal, surface finishing.
Common Uses: Architectural models, decorative items.
Most Relevant Industries: Art, architecture, consumer goods, automotive, electronics.
Pros: Low-cost materials, large parts possible.
Cons: Limited material choice, lesser accuracy.
8. Some emerging AM technologies
Mold Slurry Deposition (MoldJet)
Mold Slurry Deposition is a powder-free metal and ceramic AM technique. It combines two manufacturing processes to flexibly create bespoke parts. These processes operate sequentially in a layer-by-layer fashion. Initially, the mold is crafted layer by layer, acting as the inverse of the component's design, using inkjet print heads and a wax-like polymer. This layer of the mold is subsequently filled with a metal powder paste using a slotted nozzle.
Thanks to this step-by-step approach, it's feasible to manufacture intricate components that have undercuts or even internal passages without the necessity for support structures.
Liquid Metal Printing
Liquid Metal Printing is a material extraction technology and is similar to FDM. What differentiates it is that it uses either extremely hot nozzles or electromagnetic fields to melt and deposit pure metal wires. Its powder-free nature and expected low cost gives this technology potential for wider use.
Hamburg-based consulting company AMPOWER has extremely useful infographics on Polymer, Metal and Ceramic Additive Manufacturing under this link: https://ampower.eu/infographics/
Additive Manufacturing Technologies poster of HUBS gives a higher-level overview: https://www.hubs.com/get/am-technologies/
The classic textbook Additive Manufacturing Technologies by Ian Gibson et al: https://link.springer.com/book/10.1007/978-1-4939-2113-3