Understand the main categories of additive manufacturing and detailed explanations of each 3D printing method currently used across various industries.
Table of Contents
Introduction
Photopolymerization 3D Printing Technology (SLA, DLP, CDLP)
Powder Bed Fusion (PBF)
Fused Deposition Modeling (FDM)
Material Jetting Technology
Binder Jetting Technology
Direct Energy Deposition (LENS, EBAM)
Introduction
Choosing the most suitable 3D printing (additive) manufacturing technology (AM) for a particular application can be challenging.
The range of available 3D printing technologies and materials is very broad, often meaning that many are feasible, but each offers variations in dimensional accuracy, surface
finish, and post-processing requirements.
The goal of this article is to categorize and summarize the differences between each additive (3D printing) manufacturing technology. We define the most popular 3D printing processes, as well as their most common
applications and materials.
Photopolymerization 3D Printing Technology
Photopolymerization occurs when photopolymer resins are exposed to light of a specific wavelength and undergo a chemical reaction to become solid. More details about photopolymerization can be found here. Many additive technologies use this phenomenon to build the first layer of solid parts layer by layer.
Some SLA printing methods print parts upside down while extracting them from the resin.
Technology
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Stereolithography (SLA) SLA uses a print platform immersed in a translucent vat filled with liquid photosensitive resin. Once the print platform is submerged, a single-point laser located inside the machine will illuminate the design's cross-sectional area (layer) through the bottom of the vat, curing the material. After the printed layer is exposed to the laser and cured, the platform rises, allowing a new layer of resin to flow beneath the part. This process is repeated layer by layer to produce a solid part. Usually, parts can improve their mechanical properties after post-curing with UV light. Click here for a complete 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) Compared to SLA, DLP follows almost the same method for producing parts. The main difference is that DLP uses a digital light projection screen to flash a single image of each layer at once. Because the projector is a digital screen, the image of each layer is composed of square pixels, thus forming layers made of small rectangular blocks called voxels. For some parts, DLP can achieve faster print times compared to SLA because each complete layer is exposed at once, rather than tracing the cross-section with a laser. Click here for a complete introduction to SLA and DLP technologies, and here for a guide on designing parts. |
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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 continuous movement of the print plate in the Z-direction (upwards). This results in faster production times because the printer does not need to stop and detach the part from the print plate after each layer is produced. |
Applications
Photopolymerization technologies excel at producing parts with fine detail and smooth surface finishes. This makes them ideal for jewelry, low-temperature injection
molding, and many dental and medical applications. The primary 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, capable of dissolving (sintering or melting) plastic or metal powders at once.
Most PBF technologies employ a mechanism to spread and smooth thin layers of powder as part of the part, so that the final part is encapsulated in powder after manufacturing.
The main variations of PBF technology come from different energy sources (e.g., laser or electron beam) and the powders used (plastic or metal).
Removing powder debris from the SLS process, with the printed part still embedded in unsintered powder.
Technology
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Selective Laser Sintering (SLS) SLS produces solid plastic parts using a laser to sinter thin layers of powdered material, one layer at a time. The process begins by 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 completely encased in unsintered powder. The part is removed from the powder, cleaned, and then ready for use or further post-processing. Click here for a complete guide on designing SLS parts. |
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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 complete melting of the powder, while DMLS heats the powder to near melting temperature until they chemically fuse together. DMLS is only suitable for alloys (nickel alloys, Ti64, etc.), while SLM can use single metal parts, such as aluminum. Unlike SLS, SLM and DMLS require support structures to reinforce the high residual stresses generated during the printing process. This helps to limit the possibility of warping and distortion. DMLS is considered the metal additive manufacturing process with the largest installed base. A complete guide to designing SLM and DMLS parts can be found here. |
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Electron Beam Melting (EBM) EBM uses a high-energy beam instead of a laser to induce fusion between metal powder particles. A focused electron beam scans a thin layer of powder, causing local melting and solidification in specific cross-sectional areas. Electron beam systems generate less residual stress in parts, resulting in less deformation 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 with 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) passes through the print area, depositing a fusing agent onto a thin layer of plastic powder. Simultaneously, a fine detailing agent that inhibits sintering is printed near the edges of the part. A high-power infrared energy passes through the print bed and the sintered areas where the fusing agent has been dispensed, while the remaining powder remains untouched. This process is repeated until all parts are completed. An article comparing the features of MJF and SLS can be found here. |
Applications
Polymer-based PBF technologies offer great design freedom because no supports are required, allowing for the creation of complex geometries. Metal and plastic PBF parts
generally have very high strength and stiffness, as well as mechanical properties comparable (and sometimes even better) than bulk materials.
A wide range of post-processing methods is available, meaning PBF parts can have very smooth surfaces, and therefore, they are often used in the manufacturing of final products.
The limitations of PBF often center on the surface roughness and internal porosity of the raw printed parts, challenges related to managing shrinkage or distortion during processing, and 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 Technology
Similar to toothpaste being squeezed out of a tube, material extrusion technology extrudes material onto a print bed through a nozzle. The nozzle follows a predetermined path layer by layer to build the object.
FDM extrudes thermoplastic from a heated nozzle into a part following a predetermined path.
Technology
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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 melts. The printer continuously moves the nozzle, depositing the molten material in 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 dimensional accuracy limitations 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 Technology
Material jetting is often compared to 2D inkjet processes. Photopolymers, metals, or waxes cure or harden under UV light or high temperatures to build parts layer by layer. The nature of the material jetting process allows for printing with multiple materials, and this capability is often used to select different (soluble) support materials during the printing phase.
A material jetting printer, illustrating how large such machines typically are.
Technology
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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 allows for completing each layer's cross-section in a fast, linear manner. As the liquids are deposited onto the print bed, they harden and are cured using UV light. Material jetting processes require support, and often print soluble materials that are easy to remove during post-processing. Click here for an introduction to material jetting. |
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Nanoparticle Jetting (NPJ) Nanoparticle Jetting (NPJ) uses a liquid containing metal nanoparticles or nanoparticle support, loaded into the printer in cartridge form, and jetted onto the print plate in very thin layers of droplets. The high temperature inside the object causes the liquid to evaporate, leaving behind the metal part. |
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Drop-On-Demand (DOD) DOD material jetting printers have two nozzles: one for depositing the build material (usually 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 manner to build the cross-sectional area of the part. These machines also incorporate a flying knife to skim off each printed layer, ensuring a perfectly smooth surface for the next layer. DOD technology is typically used for wax-like materials in investment casting/lost-wax casting and mold making applications. |
Applications
Material jetting is ideal for producing realistic prototypes, offering excellent detail, high precision, and a smooth surface finish.
Material jetting allows designers to use multiple colors and multiple materials in the same print. The main disadvantages of material jetting technology are its high cost and the brittle mechanical properties caused by UV-active photopolymers.
| Technology | Common Manufacturers | Materials |
| Material Jetting | Stratasys (PolyJet), 3D Systems (MultiJet) | Rigid, Transparent, Multi-color, Rubber-like, ABS-like. Offers multi-material and multi-color printing. |
| Nanoparticle Jetting (NPJ) | Xjet | Stainless Steel, Ceramics |
| Drop-On-Demand (DOD) | Solidscape | Wax |
Binder Jetting Technology
The binder jetting process involves dispensing a binder onto a powder bed to build a portion of a layer at a time. These printed layers bond together to form solid components.
Binder jetting parts removed from the print powder.
Technology
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Binder Jetting Binder jetting bonds a binder to thin layers of powdered material. The powdered material can be ceramic-based (e.g., glass or plaster) or metal (e.g., stainless steel). The print nozzles move across the print platform, depositing binder droplets in a similar way that a 2D printer prints ink on paper, to create each layer. When a layer is completed, the powder bed moves down, and a new layer of powder is spread over the build area. This process is repeated until all parts are completed. After printing, the parts are in a green state and require additional post-processing before they are ready for use. Typically, an infiltrant is added to improve the mechanical properties of the parts. Infiltrants are usually cyanoacrylate adhesives (in the case of ceramics) or bronze (in the case of metals). |
Applications
Ceramic binder jetting is ideal 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 Material, Plaster |
| ExOne | Stainless Steel, Ceramics, Cobalt Chrome, Tungsten Carbide |
Direct Energy Deposition
Direct Energy Deposition (DED) creates parts by melting powdered material as it is deposited.
It is mainly used for 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, powder delivery nozzle, and inert gas tube, to melt the powder as it is ejected from the powder jet nozzle, forming solid parts layer by layer. The laser creates a molten pool in the print area, and powder is jetted into the pool, where it melts and then solidifies. The base layer 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 produce metal parts using metal powder or wire, which are welded together using an electron beam as a heat source. Parts are produced in a similar way to LENS, but the electron beam is more efficient than a laser and operates under vacuum conditions, a technology originally designed for space applications. |
Applications
DED technologies are specifically used in metal additive manufacturing. The nature of the process itself means they are 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 |
Source:https://www.3dhubs.com/knowledge-base/additive-manufacturing-technologies-overview#/powder-bed-fusion