Understand the main categories of additive manufacturing and a detailed explanation of each 3D printing method currently used across various industries.
Table of Contents
Introduction
Photopolymerization 3D Printing Technologies (SLA, DLP, CDLP)
Powder Bed Fusion (PBF)
Fused Deposition Modeling (FDM)
Material Jetting Technologies (Material Jetting, NPJ, DOD)
Binder Jetting Technologies
Direct Energy Deposition (LENS, EBAM)
Introduction
Choosing the most suitable3D printing (additive) manufacturing technology (AM) for a specific application can be difficult.
The range of available 3D printing technologies and materials is very broad, meaning that while many may seem suitable, each offers variations in dimensional accuracy, surface
finish, and post-processing requirements.
This article aims to categorize and summarize the differences between each additive (3D printing) manufacturing technology. We will define the most popular 3D printing processes, along with the most common
applications and materials.
Photopolymerization 3D Printing Technologies
Photopolymerization occurs when photopolymer resins are exposed to light of a specific wavelength and undergo a chemical reaction to solidify. More details on photopolymerization can be found here. Many additive technologies utilize this phenomenon to build parts layer by layer.
Some SLA printing methods print parts upside down while drawing them out of the resin.
Technologies
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Stereolithography (SLA) SLA uses a print platform submerged in a translucent vat filled with liquid photopolymer resin. Once the print platform is submerged, a single-point laser located inside the machine irradiates the designed cross-sectional area (layer) through the bottom of the vat to cure the material. After a layer is irradiated and cured by the laser, the platform lifts, allowing a fresh layer of resin to flow beneath the part. This process is repeated layer by layer to produce a solid part. Parts typically undergo post-curing with UV light to improve their mechanical properties. Click here for a full introduction to SLA and DLP technologies, and here for a guide on how to design parts for the process. |
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Digital Light Processing (DLP) DLP follows an almost identical method to SLA for producing parts. The main difference is that DLP uses a digital light projector screen to flash a single image of each layer at once. Since the projector is a digital screen, the image of each layer is composed of square pixels, forming layers made up of small rectangular bricks called voxels. For certain parts, DLP can achieve faster print times compared to SLA, as each full layer is exposed at once, rather than tracing the cross-section with a laser. Click here for a full introduction to SLA and DLP technologies, and here for a guide on how to design parts for the process. |
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Continuous DLP (CDLP) Continuous Digital Light Processing (CDLP) (also known as Continuous Liquid Interface Production or CLIP) produces parts in exactly the same way as DLP. However, it relies on the continuous movement of the print platform in the Z-direction (upwards). This results in faster production times, as the printer does not need to stop and separate the part from the print platform after each layer is produced. |
Applications
Photopolymerization technologies excel at producing parts with fine details and excellent surface finish. This makes them ideal for jewelry, low-temperature injection
molding, and many dental and medical applications. The main limitation of photopolymerization is the brittleness of the produced parts.
| Technology | Common Manufacturers | Materials |
| SLA | Formlabs, 3D Systems, DWS | Standard, Tough, Flexible, Transparent, Castable Resins |
| DLP | B9 Creator, MoonRay | Standard and Castable Resins |
| CDLP | Carbon3D, EnvisionTEC |
Standard, Tough, Flexible, Transparent, Castable Resins |
Powder Bed Fusion (PBF) uses a heat source to create solid parts by selectively melting (sintering or fusing) plastic or metal powders layer by layer.
Most PBF technologies employ a mechanism to spread and smooth thin layers of powder for part construction, ensuring the final part is encapsulated in powder upon completion.
The main variations in PBF technology stem from the different energy sources (e.g., laser or electron beam) and the types of powder used (plastic or metal).
Removing powder debris from the SLS process, with the printed part still encased in unsintered powder.
Technologies
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Selective Laser Sintering (SLS) SLS produces solid plastic parts by using a laser to sinter thin layers of powdered material, one layer at a time. The process begins with spreading an initial layer of powder onto the print platform. The cross-section of the part is scanned and sintered by the laser, solidifying it. The print platform then descends by one layer thickness, and a new layer of powder is applied. This process is repeated until a solid part is produced. The result of this process is a part fully encased in unsintered powder. After being removed from the powder and cleaned, the part is ready for use or further post-processing. Click here for a complete guide to designing parts for SLS. |
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SLM and DMLS Selective Laser Melting (SLM) and Direct Metal Laser Sintering (DMLS) produce parts using methods similar to SLS. The main difference is that SLM and DMLS are used for the production of metal parts. SLM achieves full melting of the powder, while DMLS heats the powder close to its melting temperature until they chemically fuse together. DMLS is only suitable for alloys (nickel alloys, Ti64, etc.), whereas SLM can use single metal parts, such as aluminum. Unlike SLS, SLM and DMLS require support structures to reinforce against the high residual stresses generated during printing. This helps to limit the possibility of warping and distortion. DMLS is considered the most widely adopted metal additive manufacturing process. A complete guide to designing parts for SLM and DMLS can be found here. |
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Electron Beam Melting (EBM) EBM uses a high-energy electron beam instead of a laser to induce fusion between metal powder particles. The focused electron beam scans thin layers of powder, causing localized melting and solidification in specific cross-sectional areas. Electron beam systems generate less residual stress in parts, resulting in less distortion and requiring fewer fixtures and support structures. Additionally, EBM uses less energy and can produce layers at a faster rate than SLM and DMLS, but the minimum feature size, powder particle size, layer thickness, and surface finish are generally lower. EBM also requires parts to be produced in a vacuum, and this process can only be used for conductive materials. |
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Multi Jet Fusion (MJF) MJF is essentially a combination of SLS and material jetting technologies. A carriage equipped with inkjet nozzles (similar to those used in desktop 2D printers) moves across the print area, depositing a fusing agent onto a thin layer of plastic powder. Simultaneously, a detailing agent that inhibits sintering is printed near the edges of the part. A high-power infrared energy source then passes over the print platform and the sintered areas, under the distribution of the fusing agent. When the remaining powder is untouched and removed, the process continues to repeat until all parts are complete. An article comparing MJF and SLS functionalities can be found here. |
Applications
Polymer-based PBF technologies offer great design freedom as they do not require supports, allowing for the creation of complex geometries. Both metal and plastic PBF parts
typically exhibit very high strength and stiffness, with mechanical properties comparable to (and sometimes even better than) bulk materials.
A wide range of post-processing methods is available, meaning PBF parts can achieve very smooth surfaces. Consequently, they are often used in the manufacturing of final products.
Limitations of PBF usually revolve around the surface roughness and internal porosity of the raw printed parts, managing shrinkage or distortion during processing, and challenges related to powder handling.
| Technology | Common Manufacturers | Materials |
| SLS | EOS, Stratasys | Nylon, Alumina, Carbon Fiber Filled Nylon, PEEK, TPU |
| SLM/DMLS | EOS, 3D Systems, Sinterit | Aluminum, Titanium, Stainless Steel, Nickel Alloys, Cobalt Chrome |
| EBM | Arcam | Titanium, Cobalt Chrome |
| MJF | HP | Nylon |
Fused Deposition Modeling (FDM)
Similar to toothpaste being squeezed out of a tube, material extrusion technologies extrude material through a nozzle onto a print platform. The nozzle follows a predetermined path, layer by layer.
FDM extrudes thermoplastic material from a heated nozzle in a predetermined path to form parts.
Technologies
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Fused Deposition Modeling (FDM) FDM (sometimes also referred to as Fused Filament Fabrication or FFF) is the most widely used 3D printing technology. FDM uses solid thermoplastic material in filament form. The filament is pushed through a heated nozzle, where it is melted. The printer continuously moves the nozzle, depositing the molten material at precise locations according to a predetermined path. As the material cools and solidifies, the part is built layer by layer. An introduction to FDM can be found here, and an FDM design guide can be found here. |
Applications
Material extrusion is a fast and low-cost method for producing plastic prototypes. Industrial FDM systems can also produce functional prototypes from engineering-grade materials.
FDM has certain limitations in dimensional accuracy and is highly anisotropic.
| Technology | Common Manufacturers | Materials |
| FDM | Stratasys, Ultimaker, MakerBot, Markforged | ABS, PLA, Nylon, PC, Fiber-reinforced Nylon, ULTEM, Exotic Filaments (wood-filled, metal-filled, etc.) |
Material Jetting Technologies
Material jetting is often compared to 2D inkjet processes. Photopolymers, metals, or waxes are cured or hardened under UV light or high temperatures to build parts layer by layer.
The nature of the material jetting process allows for multi-material printing, often choosing to print different support (soluble) materials during the printing stage.
A material jetting printer, illustrating the typical size of the machine.
Technologies
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Material Jetting Material jetting builds parts layer by layer by dispensing photopolymers from hundreds of tiny nozzles. Compared to other point-by-point deposition technologies, material jetting enables operations to complete the cross-section of each layer in a rapid, linear fashion. As the liquid is deposited onto the print platform, it hardens and is cured using UV light. Material jetting processes require support, and during fabrication, soluble materials that are easily removed during post-processing are typically printed. Click here for an introduction to material jetting. |
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Nanoparticle Jetting (NPJ) Nanoparticle Jetting (NPJ) uses liquid containing metal nanoparticles or nanoparticle supports, loaded into the printer in cartridge form, and jetted onto the print tray in very thin layers of droplets. High temperatures within the object cause the liquid to evaporate, leaving behind the metal part. |
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Drop-on-Demand Printing (DOD) DOD material jetting printers have two nozzles: one for depositing the build material (typically a wax-like liquid) and another for a soluble support material. Similar to traditional AM technologies, DOD printers follow a predetermined path and deposit material in a point-by-point fashion to build the cross-sectional area of the part. These machines also employ a flying cutter, skimming each printed layer to ensure a perfectly smooth surface for the next layer. DOD technology is commonly used for wax-like materials in investment casting/lost wax casting and tooling applications. |
Applications
Material jetting is ideal for creating realistic prototypes, offering excellent detail, high precision, and a smooth surface finish.
Material jetting allows designers to print with multiple colors and multiple materials in the same print. The main drawbacks of material jetting technology are its high cost and the brittle mechanical properties caused by UV-activated photopolymers.
| Technology | Common Manufacturers | Materials |
| Material Jetting | Stratasys (PolyJet), 3D Systems (MultiJet) | Rigid, Transparent, Multi-color, Rubber-like, ABS-like. Offers printing with multiple materials and multiple colors. |
| Nanoparticle Jetting (NPJ) | Xjet | Stainless Steel, Ceramics |
| Drop-on-Demand Printing (DOD) | Solidscape | Wax |
Binder Jetting Technologies
Binder jetting technology involves dispensing a binder onto a powder bed to build parts layer by layer at a time. These printed layers bond to each other to form solid components.
Binder jetting parts removed from print powder.
Technologies
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Binder Jetting Binder jetting bonds a binder onto thin layers of powdered material. The powdered material can be ceramic-based (e.g., glass or plaster) or metallic (e.g., stainless steel). The print nozzles move across the print platform, depositing droplets of binder to print each layer in a similar way to how a 2D printer prints ink on paper. When a layer is complete, the powder bed moves down, and a new layer of powder is spread over the build area. This process repeats until all parts are complete. After printing, the parts are in a "green" state and require additional post-processing before they are ready for use. Infiltrants are often added to improve the mechanical properties of the parts. Infiltrants are typically cyanoacrylate adhesives (in the case of ceramics) or bronze (in the case of metals). |
Applications
Ceramic binder jetting is very suitable for applications that emphasize aesthetics and form: architectural models, packaging, ergonomic verification, etc.
It is not suitable for functional prototypes because the parts are very fragile. Ceramic binder jetting can also be used to manufacture molds for sand casting.
Metal binder jetting parts can be used as functional parts and are more cost-effective than SLM or DMLS metal parts, but they have inferior mechanical properties.
| Technology | Common Manufacturers | Materials |
| Binder Jetting | 3D Systems, Voxeljet | Silica sand, PMMA granular materials, Plaster |
| ExOne | Stainless Steel, Ceramics, Cobalt Chrome, Tungsten Carbide |
Direct Energy Deposition
Direct Energy Deposition (DED) creates parts by melting material as it is deposited.
It primarily uses metal powders or wires and is often referred to as metal deposition.
Technologies
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Laser Engineered Net Shaping (LENS) LENS utilizes a laser head, which consists of a laser, a powder distribution nozzle, and an inert gas tube. As powder is jetted from the nozzle, it is melted to form solid parts layer by layer. The laser creates a melt pool in the print area, and powder is injected into the pool, where it melts and then solidifies. The substrate is typically a flat metal plate or an existing part to which material is added (e.g., for repair). |
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Electron Beam Additive Manufacturing (EBAM) EBAM is used to create metal parts using metal powder or wire, employing an electron beam as the heat source to weld them together. It produces parts in a similar way to LENS, but an electron beam is more efficient than a laser and operates under vacuum conditions. It was originally designed for space technology. |
Applications
DED technologies are specifically used in metal additive manufacturing. The nature of these processes makes them very suitable for repairing or adding material to existing parts (such as turbine blades).
The reliance on high-density support structures makes DED unsuitable for producing parts from scratch.
| Technology | Common Manufacturers | Materials |
| Laser | Optomec | Titanium, Stainless Steel, Aluminum, Copper, Tool Steel |
| Electron Beam Additive Manufacturing | Sciaky Inc | Titanium, Stainless Steel, Aluminum, Copper Nickel, 4340 Steel |
Original Source:https://www.3dhubs.com/knowledge-base/additive-manufacturing-technologies-overview#/powder-bed-fusion