[3D Printing News] 3D Printing (Laminated Manufacturing Technology): An Overview
Learn about the main categories of additive manufacturing and explain in detail each 3D printing method currently existing in various industries.
Table of contents
introduce
Photopolymer 3D modeling technologies (SLA, DLP, CDLP)
Powder bed melt molding technology (SLS, SLM, DMLS, EBM, multi-jet fusion)
Hot melt deposition modeling (FDM) technology
Material spraying forming technology (material spraying, NPJ, DOD)
Adhesive spraying molding technology
Direct Energy Deposition (LENS, EBAM)
introduce
Choosing the most suitable 3D printing ( addition ) technology (AM) for a particular application is a difficult process.
The range of available 3D printing technologies and materials is very wide, which usually means that many of them are feasible, but each offers variations in dimensional accuracy, surface smoothness, and post-processing requirements.
The goal of this article is to categorize and summarize the differences between various layering (3D printing) manufacturing technologies. We define the most popular 3D printing processes, as well as the most common applications and materials. 
Photopolymer 3D molding technology
Photopolymerization occurs when a photopolymer resin is exposed to light of a specific wavelength and undergoes a chemical reaction to become a solid. More details about photopolymerization can be found here. Many lamination techniques utilize this phenomenon to build the first solid layer at a time. 
Some SLA printing methods involve printing parts upside down while they are being extracted from the resin.
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3D flatbed printing (SLA) SLA uses a printing platform immersed in a semi-transparent container filled with liquid photosensitive resin. Once the printing platform is submerged, a single point of laser light located inside the machine will irradiate the cured material through a cross-sectional area (layer) designed at the bottom of the tank. After the printed layer is irradiated and cured by laser light, the platform rises, allowing a new layer of resin to flow beneath the part. This process is repeated layer by layer to create a solid component. Typically, the mechanical properties of the part can be improved by post-curing with ultraviolet light. Click here for a full introduction to SLA and DLP technologies, and see a guide on how to design part processes. |
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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 digital light projection to flash a single image of each layer onto a screen one at a time. Because the projector is a digital screen, each layer of the image is composed of square pixels, thus forming layers made up of small rectangular blocks called voxels. For some components, DLP can achieve faster printing times compared to SLA because each complete layer is exposed once, rather than using laser light to trace cross-sections. Click here for a full introduction to SLA and DLP technologies, and here for a guide to the part design process. |
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Continuous DLP (CDLP) Continuous Direct 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 (upward) of the printing plate in the Z direction. This allows for faster production times because the printer does not need to stop and separate the parts from the printing plate after each layer is produced. |
application
Photopolymerization excels at producing parts with intricate details and smooth surfaces. This makes it ideal for jewelry, low-temperature injection molding, and many dental and medical applications. The main limitation of photopolymerization is the brittleness of the parts produced.
| technology | Common manufacturers | Material |
| SLA | Formlabs, 3D Systems, DWS | Standard, tough, elastic, transparent, castable resin |
| DLP | B9 Creator, MoonRay | Standard and castable resins |
| CDLP | Carbon3D, EnvisionTEC |
Standard, tough, elastic, transparent, castable resin |
Powder bed melt molding
Powder bed melt molding (PBF) uses a heat source to generate solid parts, which can dissolve (sinter or melt) plastic or metal powders in one step.
Most PBF technologies employ mechanisms to disperse and smooth thin layers of powder as part of the component, so that the final component is encapsulated in powder after manufacturing.
The main variations in PBF technology come from different energy sources (such as laser light or electron beams) and the powders (plastics or metals) used in the processing. 
Powder debris is removed during the SLS process, and the printing section remains mounted within the unsintered powder.
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Selective laser sintering (SLS) Solid plastic parts produced by SLS use laser light to sinter thin layers of powder material one layer at a time. The process begins by spreading an initial powder layer on a printing platform. The cross-section of the part is scanned and sintered by the laser light, and then solidified. The printing platform then descends one layer thicker and applies a new layer of powder. 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 then removed from the powder, cleaned, and ready for use or further post-processing. Click here to see the complete guide to SLS part design. |
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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 lies in the fact 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 its melting point until they are chemically fused together. DMLS is only suitable for alloys (nickel alloys, Ti64, etc.), while SLM can use individual metal parts, such as aluminum. Unlike SLS, SLM and DMLS require support structures to reinforce against the high residual stress generated during the printing process. This helps limit the possibility of warping and twisting. DMLS is considered the most widely installed metal conditioning base process. A complete guide to SLM and DMLS part design can be found here . |
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Electron beam melting (EBM) EBM uses a high-energy beam instead of laser light to induce fusion between metal powder particles. A focused electron beam scans a thin layer of powder, resulting in localized melting and solidification over a specific cross-sectional area. Electron beam systems generate less residual stress in parts, resulting in less deformation and requiring less fixing and support structures. Furthermore, EBM uses less energy and can produce layers at a faster rate than SLM and DMLS, but its minimum feature size, powder particle size, layer thickness, and surface smoothness 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 technology. A carriage housing inkjet nozzles (similar to those used in desktop 2D printers) deposits a flux onto a thin layer of plastic powder through the printing area. Simultaneously, a fine agent to inhibit sintering is printed near the edges of the part. A high-power infrared energy passes through the printing platform and sintering site, and under the distribution of the flux, the remaining powder leaves before it comes into contact with the flux. This process is repeated until all parts are completed. Here you can find an article comparing the features of MJF and SLS. |
application
Polymer-based PBF technology offers great design freedom because it eliminates the need for supports, allowing for the fabrication of complex geometries. Both metal and plastic PBF parts typically possess very high strength and rigidity, as well as mechanical properties comparable to (and sometimes even better than) those of bulk materials.
There are a wide range of post-processing methods available, which means that PBF parts can have very smooth surfaces, so they are often used in the manufacture of final products.
Limitations of PBF typically focus on the surface roughness and internal porosity of the original printed parts, handling shrinkage or deformation during the manufacturing process, and challenges related to powder handling.
| technology | Common manufacturers | Material |
| SLS | EOS, Stratasys | Nylon, alumina, carbon fiber filled nylon, PEEK, TPU |
| SLM/DMLS | EOS, 3D Systems, Sinterit | Aluminum, titanium, stainless steel, nickel alloy, cobalt-chromium alloy |
| EBM | Arcam | Titanium, cobalt-chromium alloy |
| MJF | HP | nylon |
Hot melt deposition modeling technology
Similar to toothpaste being squeezed out of a tube, material extrusion technology uses nozzles to extrude material onto a printing plate. The nozzles are built up layer by layer following a predetermined path. 
FDM extrudes thermoplastic material from a heated nozzle through a predetermined path to form parts.
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Hot melt deposition modeling (FDM) technology FDM (sometimes called fused wire fabrication or FFF) is the most widely used 3D printing technology. FDM uses a solid thermoplastic material, presented in filament form. The filament is pushed through a heated nozzle, where it is melted. The printer continuously moves the nozzle, placing the molten material at precise locations along a predetermined path. As the material cools and solidifies, the part is built up layer by layer. A complete guide to FDM can be found here , and an FDM design guide can be found here. |
application
Material extrusion is a fast and low-cost method for producing plastic prototypes. Industrial FDM systems can also produce prototypes and functional prototypes from engineering samples.
FDM has certain limitations in dimensional accuracy and is highly anisotropic.
| technology | Common manufacturers | Material |
| FDM | Stratasys, Ultimaker , MakerBot, Markforged | ABS , PLA , Nylon , PC , Fiber-reinforced Nylon, ULTEM, and dissimilar materials (wood-filled, metal-filled, etc.) |
Material spraying forming technology
Material spraying is often compared to 2D inkjet printing. Photopolymers, metals, or waxes can be cured or hardened under ultraviolet light or high temperatures to create a single layer of part. The nature of material spraying allows for the printing of a variety of materials, a capability often achieved by selecting different support (solution) materials during the printing stage. 
A material spraying printing machine describes its typical size.
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Material spraying involves dispensing photosensitive polymers layer by layer from hundreds of tiny nozzles to form parts. Compared to other point-by-point deposition techniques, material spraying allows for the rapid, linear completion of each layer's cross-section. When liquids settle onto the printing platform, they harden and are then cured using ultraviolet light. The material spraying process requires support and typically involves printing easily removable, soluble materials during post-processing. Click here to see an introduction to material spraying. |
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Nanoparticle spraying (NPJ) Nanoparticle spraying (NPJ) uses a liquid containing metal nanoparticles or nanoparticle-supported particles, loaded into the printer in cartridge form, and sprayed onto the printing disk as a very thin layer of droplets. The high temperature inside the object causes the liquid to evaporate, leaving behind the metal parts. |
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Drip-on-Demand Printing (DOD) DOD (Dependency Oxidation) material jet printers have two nozzles: one for depositing the constituent material (usually a waxy liquid) and the other for a soluble support material. Similar to traditional AM (Advanced Motion) technology, DOD printers deposit material point-by-point along a predetermined path to build the cross-sectional area of the part. These machines also employ a fly knife to remove the printed layer from each area, ensuring a perfectly smooth surface for the next layer. DOD technology is commonly used in lost-wax casting/investment casting applications involving wax-like materials and mold making. |
application
Material spraying is ideal for creating realistic prototypes, as it provides excellent detail, high refinement, and a smooth finish.
Material spraying allows designers to use multiple colors and materials in a single print. The main drawbacks of material spraying technology are its high cost and the embrittlement of mechanical properties caused by UV-active photopolymers.
| technology | Common manufacturers | Material |
| Material spraying | Stratasys (polymer spraying), 3D Systems (multi-nozzle spraying) | Rigid, transparent, multi-colored, rubber-like, ABS-like. Available in a variety of materials and colors for printing. |
| Nanoparticle spraying (NPJ) | Xjet | Stainless steel, ceramic |
| Drip-on-Demand Printing (DOD) | Solidscape | wax |
Adhesive spraying molding technology
The adhesive spraying process involves distributing adhesive onto a powder bed, building up a layer at a time. These printed layers bond together to form a solid composition. 
Parts coated with adhesive removed from printing powder
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Adhesive spraying involves bonding an adhesive to a thin layer of powder material. The powder material can be ceramic-based (e.g., glass or plaster) or metal (e.g., stainless steel). The print nozzle moves across the print platform, depositing adhesive droplets and printing each layer in a similar manner to how a 2D printer prints ink on paper. Once one layer is completed, the powder bed moves downwards, and a new layer of powder is applied to the build area. This process repeats until all parts are finished. After printing, the part is in a green state and requires additional post-processing before it is ready for use. Adding impregnating agents usually improves the mechanical properties of parts. Impregnating agents are typically cyanoacrylate adhesives (in the case of ceramics) or bronze (in the case of metals). |
application
Ceramic adhesive spraying is ideal for applications that showcase aesthetics and form: architectural models, packaging, ergonomic verification, etc.
It is not suitable for functional prototypes because the parts are very fragile. Ceramic adhesive spraying can also be used to manufacture molds for sand casting.
Metal adhesive sprayed parts can be used as functional parts and are more cost-effective than SLM or DMLS metal parts, but have poorer mechanical properties.
| technology | Common manufacturers | Material |
| Adhesive spraying | 3D Systems, Voxeljet | Silica sand, PMMA granules, gypsum |
| ExOne | Stainless steel, ceramics, cobalt-chromium alloys, tungsten carbide |
Direct Energy Deposition
Direct energy deposition (DED) creates parts by melting powder materials during the deposition process.
It is primarily used for metal powders or wires and is commonly referred to as metal deposition.
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Laser-engineered net shape (LENS) LENS utilizes a laser head, which consists of a laser head, a powder dispensing nozzle, and an inert gas tube. When the powder is ejected from the nozzle, it melts the powder to form solid parts layer by layer. The laser beam creates a molten pool in the printing area, into which the powder is injected, melts, and then solidifies. The base layer is typically a flat metal sheet or an existing part to which additional material is added (e.g., for repair). |
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Electron Beam Augmentation Manufacturing (EBAM) EBAM is used to manufacture metal parts using metal powder or wire, and is welded together using an electron beam as a heat source. Similar to LENS, parts are manufactured using electron beams, which are more efficient than lasers and operate under vacuum conditions—a technology originally designed for space applications. |
application
DED technology is specifically used in the manufacture of metal additives. The process itself means that it is very suitable for repairing or adding materials 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 | Material |
| laser | Optomec | Titanium, stainless steel, aluminum, copper, tool steel |
| Electron beam increases 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