One challenge faced by many new 3D printing users is the inability to differentiate between different types of 3D printing processes. It would be too limiting to think that 3D printing is just plastic extruded from a hot nozzle and stacked into shapes, but it is actually much more than that!
In fact, 3D printing, also known as additive manufacturing, is an umbrella term that covers a number of distinct 3D printing processes that use entirely different machines and materials. When we think about some of the things that are 3D printed today, from pencil holders to rocket engines, you realize that these technologies are very different, but also have some key things in common. For example, all 3D printing starts with a digital model, and because the technology is inherently digital, parts or products are initially designed using computer-aided design (CAD) software or electronic files obtained from digital parts repositories. The design file is then put into special build preparation software that breaks it down into slices or layers to be 3D printed, which converts the model into slices and generates path instructions for the 3D printer to follow.
Types of additive manufacturing can be divided based on what they produce or the type of materials they use, but in order to apply construction to the technology worldwide, the International Standards Organization (ISO) divides it into seven general types: material extrusion, Reductive polymerization, powder bed fusion, material jetting, binder jetting, directed energy deposition and sheet lamination. In this article, you will learn the differences between these technologies and the typical applications of each.
1 Material extrusion
Material extrusion is exactly what it sounds like: material is extruded through a nozzle. Typically, the material is plastic filament through a heated nozzle, melting it in the process. The printer deposits the material onto the printing platform along a path determined by the slicing software. on, the filament then cools and solidifies to form a solid, which is the most common form of 3D printing.
This is an extremely broad category considering there are almost no limits to the materials that can be extruded, including plastics, metal slurries, concrete, biogels and various food products. The price of this type of 3D printer ranges from a few hundred yuan to seven figures.
Subtypes of Material Extrusion: Fused Deposition Modeling (FDM), Architectural 3D Printing, Micro 3D Printing, Bio-3D Printing
Material: plastic, metal, food, concrete, etc.
Dimensional accuracy: ±0.5% (lower limit ±0.5mm)
Common applications: Prototypes, electrical enclosures, form and fit testing, jigs and fixtures, investment casting patterns, houses, etc.
Pros: Lowest cost 3D printing method, wide range of materials
Disadvantages: Material properties (strength, durability, etc.) are often lower and dimensions are often less precise
1.1 Fused Deposition Modeling (FDM)
FDM, like all 3D printing technologies, starts with a digital model, which is then converted into instructions for the 3D printer to follow. With FDM, a spool of filament (or multiple at a time) is loaded into the 3D printer and fed A printer nozzle in the extrusion head is heated to the required temperature, causing the filament to soften so that successive layers will join together to form a strong part.
As the printer moves the extrusion head along the specified coordinates in the Build until the object is fully formed. Depending on the geometry of the object, it is sometimes necessary to add support structures to support the model while printing. For example, if the model has steep overhangs, these supports will be removed after printing. There are also support structure materials that can be dissolved in water or other solutions. middle.
1.2 Bio-3D printing
3D bioprinting is an additive manufacturing process that combines organic or biological materials (such as living cells and nutrients) to create three-dimensional structures that resemble natural tissues. In other words, bioprinting is a type of 3D printing that can produce from Anything from bone tissue to blood vessels to living tissue, it is used in a variety of medical research and applications, including tissue engineering, drug testing and development, and innovative regenerative medicine therapies. The actual definition of 3D bioprinting is still evolving. In essence, 3D bioprinting works similarly to FDM 3D printing and belongs to the material extrusion family, although extrusion is not the only bioprinting method.
3D bioprinting uses materials expelled from a needle to create layers. These materials, called bioinks, are primarily composed of living substances such as cells in a carrier material (such as collagen, gelatin, hyaluronic acid, silk, alginate or nanocellulose), which provide support for molecular scaffolding for structural growth and nutrient uptake.
1.3 Architectural 3D printing
Architectural 3D printing is a rapidly growing field of material extrusion. The technology involves using extremely large 3D printers (often tens of meters tall) to extrude building materials such as concrete from nozzles, with these machines often taking the form of gantry or robotic arm systems. Today, 3D architectural printing technology is used in homes, architectural features and construction projects from wells to walls, and some academics say it has the potential to significantly disrupt the entire construction industry because it reduces the need for labor and reduces construction waste.
There are dozens of 3D printed houses in the United States and Europe, and research is underway to develop 3D construction technology that will use materials found on the moon and Mars to build habitats for future expeditions, printing with local soil instead of concrete. More sustainable construction methods are always in the spotlight.
2 Restore aggregation
Vat polymerization (also known as resin 3D printing) is a series of 3D printing processes that use a light source to selectively cure (or harden) photopolymer resin in a vat. In other words, light is directed precisely to specific points or areas of the liquid plastic to harden it. After the first layer is cured, the build platform is moved up or down a small amount (usually between 0.01 and 0.05 mm), the next layer is cured, the previous layer is attached, and the process is repeated layer by layer until a 3D part is formed. Once the 3D printing process is complete, the object is cleaned to remove remaining liquid resin and post-cured (in sunlight or in a UV chamber) to enhance the part’s mechanical properties.
The three most common forms of reduction polymerization are stereolithography (SLA), digital light processing (DLP), and liquid crystal display (LCD) (also known as mask stereolithography (MSLA)). Between these types of 3D printing technologies The fundamental difference is the light source and how it is used to cure the resin. Some 3D printer manufacturers, especially those making professional-grade 3D printers, have developed unique and patented variations of barrel polymerization, so you may see different names for the technology on the market. Industrial 3D printer maker Carbon uses a vat polymerization technology called digital light synthesis (DLS), Stratasys’ Origin calls its technology programmable photopolymerization (P³), and Formlabs offers so-called low-force stereolithography (LFS). Azul 3D was the first to commercialize reduction polymerization in the form of large area rapid printing (HARP), as well as photolithography-based metal manufacturing (LMM), projection microstereolithography (PµSL) and digital composite manufacturing (DCM). This is a filled photopolymer technology that introduces functional additives such as metal and ceramic fibers into the liquid resin.
Types of 3D printing technologies: stereolithography (SLA), liquid crystal display (LCD), digital light processing (DLP), microstereolithography (μSLA), etc.
Material: Photopolymer resin (castable, transparent, industrial, biocompatible, etc.)
Dimensional accuracy: ±0.5% (lower limit ±0.15 mm or 5 nm, using μSLA)
Common applications: Injection molded polymer prototypes and end-use parts, jewelry casting, dental applications, consumer products
Advantages: Smooth surface, fine feature details
2.1 Stereolithography (SLA)
Stereolithography was invented in 1986 by Chuck Hull, who patented the technology and founded 3D Systems to commercialize it, making it now available to hobbyists and professionals from numerous 3D printer manufacturers. technology. SLA printers use mirrors, called galvanometers or galvanometers, one on the X-axis and the other on the Y-axis. These galvanometers quickly pass a laser beam (or two) through the resin, selectively curing and solidifying it. cross-section of the object within that area and building it layer by layer, as each layer solidifies in the right place it moves up to pull out the hardened layer of resin and make room for another layer of liquid and then Cured by laser.
Most SLA printers use a solid-state laser to cure the part. One disadvantage of this version of polymerization is that the point laser may take longer to trace the cross-section of the object compared to our next method (DLP), which One method uses a flash of light to instantly harden the entire layer, however, lasers can produce the stronger light required for some engineering-grade resins.
2.1.1 Microstereolithography (μSLA)
As the name suggests, this version of SLA belongs to the vat polymerization family, which can print microscopic parts, or resolutions between 2 microns and 50 microns. For reference, the average width of a human hair is 75 microns. One of the so-called “micro-3D printing” technologies, µSLA involves exposing a photosensitive material (liquid resin) to a UV laser. The difference is the use of specialized resins, advanced lasers, and the addition of lenses, which create virtually Incredible little dots of light.
2.1.2 Two-photon polymerization (TPP)
Another micro 3D printing technology, TPP (also known as 2PP), can be classified as SLA because it also involves lasers and photosensitive resins. It can print smaller parts than µSLA, as small as 0.1 microns. TPP uses pulsed femtosecond lasers. Focuses on a narrow spot in a special resin, then uses that spot to cure individual 3D pixels (also called voxels) in the resin. By solidifying these small nanometer to micron voxels sequentially, layer by layer, in a predefined path, you can create 3D objects that can be several millimeters large while maintaining nanometer resolution.
TPP is currently used in research, medical applications and the manufacture of microscopic parts such as microelectrodes and optical sensors.
2.2 Digital Light Processing (DLP)
DLP 3D printing uses a digital light projector (rather than a laser) to simultaneously flash a single image of each layer on the resin (or multiple flashes for larger parts). DLP is used to produce larger parts or more parts in a single batch because each layer of flashing takes the exact same time no matter how many parts are built, making it generally faster than the laser method in SLA. Since the projector is a digital screen, each layer’s image is made up of square pixels, resulting in a layer made up of small rectangular blocks called voxels, which use a light-emitting diode (LED) screen or a UV light source to project light onto the resin. , and projects light onto the build surface through a digital micromirror device (DMD).
DMD sits between the light and the resin and consists of a series of micromirrors that control where the light is projected and generate light patterns on the build surface. This allows the resin to have different light spots (and polymerization) at different locations within a layer. ). Modern DLP projectors typically use thousands of micron-sized LEDs as light sources. Their on and off states are individually controlled and allow for increased XY resolution. Not all DLP 3D printers are the same. The power of the light source, the The quality of the lens and DMD determines the price of the printer.
Additionally, there are some DLP 3D printers that have a light source mounted on top of the printer, shining down onto the resin rather than up. These “top-down” machines flash a layer of images from the top, solidify one layer at a time, and then The cured layer is placed back into the tank, and each time the build platform is lowered, a recoater mounted on top of the tank moves back and forth over the resin to smooth out the new layer. The manufacturer states that this method can provide a more stable part output for larger prints because the printing process is not against gravity. When printing from the bottom up, there is a limit to the weight that can hang vertically on the build platform while the resin The slots also support the print while printing, reducing the need for support structures.
2.2.1 Projection microstereolithography (PµSL)
PμSL is itself a unique type of slot aggregation and we will add PμSL here as a subcategory of DLP. Another micro-3D printing technology, PμSL uses ultraviolet light from a projector to solidify specially formulated resin layers at the micron level (2 micron resolution and 5 micron layer height). This additive manufacturing technology is known for its low cost, accurate Continuing to develop due to its high performance, high speed, and wide range of materials that can be used (including polymers, biomaterials, and ceramics), it has shown great potential in applications in microfluidics and tissue engineering, microoptics, and biomedical microdevices.
2.2.2 Lithography-based metal manufacturing (LMM)
Another category of DLP, this method of 3D printing using light and resin can create microscopic metal parts suitable for applications such as surgical tools and micromachined parts. In LMM, metal powder is evenly dispersed in photosensitive resin and then exposed to blue light through a projector for selective polymerization. After printing, the polymer component of the “green” part is removed, leaving an all-metal “brown” part, which is The entire process is completed by sintering in a furnace. Raw materials include stainless steel, titanium, tungsten, brass, copper, silver and gold.
2.3 Liquid crystal display (LCD)
Liquid Crystal Display (LCD), also known as Mask Stereolithography (MSLA), is very similar to the DLP above, except that it uses an LCD screen instead of a Digital Micromirror Device (DMD), which has a significant impact on the price of the 3D printer. Significant impact. Like DLP, LCD photomasks display digitally and are made up of square pixels. The pixel size of the LCD photomask determines the granularity of the print. Therefore, the XY accuracy is fixed and does not depend on the degree of zoom or zoom of the lens ( Unlike the case with DLP).
Another difference between DLP-based printers and LCD technology is that the latter uses arrays of hundreds of individual emitters rather than single-point emitter light sources like laser diodes or DLP bulbs. Similar to DLP, LCD can achieve faster print times than SLA under certain conditions because the entire layer is exposed at once, rather than tracing a cross-sectional area with a laser spot. Due to the low cost of LCD units, the technology has become the technology of choice in the field of cheap desktop resin printers, but this does not mean that it is not used by professionals. Some industrial 3D printer manufacturers are pushing the limits of technology and achieving impressive results. Results.
3 powder bed fusion
Powder bed fusion (PBF) is a 3D printing process in which a heat source selectively melts powder particles (plastic, metal or ceramic) within the build area to create a solid object layer by layer. Powder bed fusion 3D printers typically use blades, rollers, and wipers to lay down a thin layer of powder material on the print bed. Energy (usually from a laser) fuses specific points on the powder layer, and then another powder layer is deposited and fused to the previous layer. layer, and the process is repeated until the entire object is manufactured, with the final product being enveloped and supported by the unmelted powder. Although the process varies depending on whether the material is plastic or metal, PBF can create parts with high mechanical properties, including strength, wear resistance and durability, for end-use applications in consumer products, machinery and tools. Although 3D printers in this field are becoming increasingly affordable (with starting prices hovering around $25,000), it is still considered a professional or industrial technology.
Types of 3D printing technologies: Selective Laser Sintering (SLS), Laser Powder Bed Fusion (LPBF), Electron Beam Melting (EBM)
Material: plastic powder, metal powder, ceramic powder
Dimensional accuracy: ±0.3% (lower limit ±0.3mm)
Common applications: functional parts, complex pipes (hollow design), small batch parts production
Advantages: Functional components, excellent mechanical properties, complex geometries
Disadvantages: Higher machine costs, typically higher material costs, slower build speeds
3.1 Selective laser sintering (SLS)
Selective laser sintering (SLS) uses a laser to create objects from plastic powder. First, a box of polymer powder is heated to a temperature just below the melting point of the polymer. Next, a recoating blade or wiper deposits a very thin layer of powdered material (usually 0.1 mm thick) on the build platform. A laser (CO2 or fiber optic) then begins scanning the surface according to a pattern laid out in the digital model, with the laser selectively sintering the powder and solidifying cross-sections of the object. As the entire cross section is scanned, the build platform moves down one layer in height, the recoat blade deposits a new layer of powder on top of the most recently scanned layer, and the laser sinteres the next cross section of the object onto the previously cured cross section. superior. Repeat these steps until all objects are manufactured. The unsintered powder remains in place to support the object. This reduces or eliminates the need for support structures. Once the part is removed from the powder bed and cleaned, no other post-processing steps are required. The part can be polished, coated or stained.
There are dozens of differentiating factors for SLS 3D printers, including not only their size, but also the power and number of lasers, the spot size of the lasers, when and how the bed is heated, and how the powder is distributed. The most common material used in SLS 3D printing is nylon (PA6, PA12), but flexible parts can also be printed using TPU and other materials.
3.1.1 Micro-selective laser sintering (μSLS)
μSLS may be classified as SLS or laser powder bed fusion (LPBF) as described below. It uses a laser to sinter a powdered material, like SLS, but the material is usually metal rather than plastic, so it’s more like LPBF. Anyway, it’s another micro 3D printing technology that can print at the micron level (below 5 μm). Create parts at the resolution. In μSLS, a layer of metal nanoparticle ink is applied to a substrate and then dried to produce a uniform layer of nanoparticles. Next, a laser patterned with a digital micromirror array is used to heat and sinter the nanoparticles into the desired pattern, and then repeat this set of steps to build each layer of the 3D part in the μSLS system.
3.2 Laser powder bed fusion (LPBF)
With the most aliases of all 3D printing technologies, this metal 3D printing method is formally known as laser powder bed fusion (LPBF) and is also widely known as direct metal laser sintering (DMLS) and selective laser melting ( SLM). A subtype of powder bed fusion, LPBF involves a bed of metal powder and one or more high-power lasers (up to 12). LPBF 3D printers use lasers to selectively fuse metal powders together layer by layer on a molecular basis until the model Complete, LPBF is a highly precise 3D printing method commonly used to create complex metal parts for aerospace, medical and industrial applications.
Like SLS, the LPBF 3D printer starts with a digital model divided into multiple slices. The printer loads the powder into the build chamber and then spreads it across the build plate with a recoat blade (like a windshield wiper) or roller. In thin layers, the laser traces the layers onto the powder. The build platform then moves down, applying another layer of powder and fusing it to the first layer until the entire object is built. The build chamber is closed, sealed, and in most cases filled with an inert gas, such as a nitrogen or argon mixture, which ensures the metal does not oxidize during the melting process and helps clear debris from the melting process.
Filling powder on the print bed provides some support for the model during the printing process, and unused metal powder can be reused for the next print. After printing, the part is removed from the powder bed, cleaned, and often undergoes a secondary heat treatment to relieve stress, and the remaining powder is recovered and reused. Differentiating factors for LPBF 3D printers include the type, intensity, and number of lasers. Small LPBF printers typically have one 30-watt laser, while industrial versions typically have 12 1,000-watt lasers. LPBF machines use common engineering alloys such as stainless steel, nickel superalloys and titanium alloys, with dozens of metals available for the LPBF process.
3.3 Electron beam melting (EBM)
EBM, also known as electron beam powder bed fusion (EPBBF), is a metal 3D printing method similar to LPBF, but uses an electron beam instead of a fiber laser. The technology is used to make titanium orthopedic implants, jet engines Parts such as turbine blades and copper coils. There are several reasons to choose EBM over laser-based metal 3D printing. First, electron beams generate more power and heat, which are needed for some metals and applications. Second, EBM is performed not in an inert gas environment but in a vacuum chamber to prevent beam scattering, and the build chamber temperature can reach up to 1000°C, and in some cases even higher. Finally, because the electron beam is steered using an electromagnetic beam, it can move at a higher speed than a laser and can even be separated to expose multiple areas simultaneously.
One of the advantages of EBM over LPBF is its ability to handle conductive materials and reflective metals such as copper. Another feature of EBM is the ability to nest or stack individual parts on top of each other in the build chamber, as they do not necessarily have to be connected to the build plate, which greatly increases throughput. Electron beams typically produce greater layer thicknesses and less detailed surface features than lasers, and EBM-printed parts may not require post-print heat treatment to relieve stress due to high temperatures in the build chamber.
4 material jetting
Material jetting is a 3D printing process in which tiny droplets of material are deposited onto a build plate and then solidify, or solidify, to build objects one layer at a time using droplets of photopolymer or wax that solidify when exposed to light. The nature of the material jetting process allows different materials to be printed on the same object, so the main application of this technology is to create parts in a variety of colors and textures.
Types of 3D printing technology: Material Jetting (MJ), Nanoparticle Jetting (NPJ)
Materials: Photopolymer resin (standard, castable, clear, high temperature), wax
Dimensional accuracy: ±0.1mm
Common applications: full-color product prototypes, injection mold prototypes, small batch injection molds, medical models, fashion
Pros: Textured surface finish, full color and multiple material options
Disadvantages: Limited materials, not suitable for demanding mechanical parts, higher cost than other resin technologies
4.1 Material Jetting (M-Jet)
Polymer Material Jetting (M-Jet) is a 3D printing process in which a layer of photosensitive resin is selectively deposited onto a build plate and cured with ultraviolet (UV) light. After one layer is deposited and cured, the build platform is lowered one layer Thickness, and repeating the process to build 3D objects, M-Jet combines the outstanding detail of resin 3D printing with the speed of filament 3D printing (FDM) to create parts and prototypes with realistic colors and textures.
M-Jet machines deposit build material from multiple rows of print heads in a row-by-row fashion. This method enables the printer to manufacture multiple objects on a single production line without affecting build speed, as long as the models are correctly lined up on the build platform and each By optimizing the space within the build line, the M-Jet can produce parts faster than many other types of resin 3D printers. Objects made with M-Jet require supports. The supports are printed simultaneously with dissolvable materials during the build process. The dissolvable materials are removed during post-processing. M-Jet is the only model that offers multi-material printing. Unlike 3D printing technology for full-color objects, unlike reduction polymerization technology, M-Jet does not require post-curing because the UV rays in the printer will completely cure each layer.
4.1.1 Aerosol spray
Aerosol Jet is a unique technology developed by Optomec. It is mainly used for 3D printing electronic products. Components such as resistors, capacitors, antennas, sensors and thin film transistors are all printed using Aerosol Jet technology. It can be roughly compared to spray paint, but it differs from industrial coating processes in that it can be used to print fully 3D objects. The e-ink is put into an atomizer, which produces a thick layer of particles with a diameter of 1 to 5 microns. The aerosol mist, which contains droplets of material, is then delivered to the deposition head where it is focused by the sheath gas, creating a high-velocity particle spray. Because of the energy method, this technique is sometimes classified as directed energy deposition, but since the material is in droplet form in this case, we include it under material ejection.
4.1.2 Plastic free forming
The German company Arburg has created a technology called Plastic Free Forming (APF), which is a cross between extrusion technology and material injection technology. It uses commercially available plastic pellets that are melted during the injection molding process and moved to the discharge device. The high-frequency nozzle closure produces a rapid opening and closing movement, which can produce up to 200 pieces per second with a diameter between 0.2 and 0.4 mm. Tiny plastic droplets in between, the droplets combine with the hardened material as they cool. Generally speaking, no post-processing is required, but if support material is used, it must be removed.
4.2 Nanoparticle jet (NPJ)
Nanoparticle jetting (NPJ), one of the few proprietary technologies that defies simple classification, uses an array of printheads with thousands of inkjet nozzles to simultaneously drop millions of ultrafine materials in ultrathin layers form is sprayed onto the build pallet, along with the support material. The resulting 3D parts retain only small amounts of binder, which is removed during post-sintering processing.
5 Adhesive jetting
Binder jetting is a 3D printing process in which a liquid adhesive selectively bonds areas in a powder layer. The technology uses powdered materials (metals, plastics, ceramics, wood, sugar, etc.) Liquid materials, whether metal, plastic, sand or other powdered materials, the binder jetting process is essentially the same. First, a recoating blade or roller coats the build platform with a thin layer of powder. Then, a printhead with an inkjet nozzle passes over the bed, selectively depositing droplets of adhesive or fusing agent to apply the The powder particles bond together, and when that layer is complete, the build platform moves down and a blade or roller recoats the surface, and the process repeats until the entire part is complete. At the end of the print the parts are wrapped in a bed of powder material which needs to be scooped out and the excess powder is collected and can be reused.
Depending on the material, post-processing is required, with the exception of sand, which can usually be used directly as a printer core or mold. When the powder is metal or ceramic, post-processing involving heat will melt away the binder, leaving only Lower metal, plastic part post-processing includes a curing stage and often includes coatings to improve surface finish, in addition to polishing, painting and sanding of polymer adhesive sprayed parts. Binder jetting has long been considered a “cold” technology because, unlike using lasers or electron beams on powdered metals or polymers, there is no heat in the process prior to post-processing. However, the situation may change when we talk about polymer binder jetting.
Binder jetting is fast and productive, so it can produce high volumes of parts more cost-effectively than other additive manufacturing methods. Metal binder jetting is suitable for a variety of metals and is popular in end-use consumer goods, tooling, and bulk spare parts. Cold polymer binder jetting has limited material options and produces parts with lower structural properties, but with heat Different nylon and TPU are usually used.
Subtypes of 3D printing technologies: Metal binder jetting, polymer binder jetting, sand binder jetting, multi-jet fusion, high-speed sintering, selective absorption fusion
Materials: sand, polymers, metals, ceramics, etc.
Dimensional accuracy: ±0.2 mm (metal) or ±0.3 mm (sand)
Common applications: Functional metal parts, full-color models, sand castings and molds
Pros: Low cost, high build volume, functional metal parts, excellent color reproduction, fast print speeds, support-free design flexibility
Disadvantages: This is a multi-step process for metals, and polymer parts made with cold processing are not as mechanically strong
5.1 Metal binder jetting
Binder jetting is also used to create solid metal objects with complex geometries, well beyond the capabilities of traditional manufacturing techniques. Metal binder jetting is a very attractive technology for volume metal part production and achieving lightweighting. Because binder jetting can print parts with complex pattern infills rather than solid parts, the resulting parts are significantly lighter. Lightening, while also being very strong, the porosity characteristics of adhesive jetting can also be used to enable lighter end parts for medical applications, such as implants. Overall, the material properties of metal binder jetted parts are comparable to those produced by metal injection molding, one of the most widely used manufacturing methods for mass production of metal parts. In addition, adhesive jetted parts exhibit higher surface smoothness, especially in the internal channels.
Metal binder jetted parts require secondary processing after printing to achieve good mechanical properties. When first shipped from the factory, parts essentially consist of metal pellets held together with a polymer adhesive. These so-called “green parts” are fragile and cannot be used as is. After the part is finished printing and removed from the metal powder bed (a process called depowdering), some process like thermal curing is required, and then heat treated in a furnace (a process called sintering). The printing parameters and sintering parameters are both Adjust for specific part geometry, material, and desired density. Bronze or other metals are sometimes used to penetrate the voids in binder-blasted parts to achieve zero porosity.
5.2 Plastic binder jetting (MJF, HSS, SAF)
Plastic binder jetting is very similar to metal binder jetting in that it involves both powder and liquid binders, and as we mentioned above, polymer binder jetting can be divided into cold and hot processes. Polymer binder jetting begins by distributing a polymer powder (usually a type of nylon) in a thin layer onto a build platform. The inkjet head then sprays the adhesive-like glue (or other fluid, including colored ink, fusible or radiation-absorbing fluids and magnetic fluids) are dispensed exactly where the polymers on each layer should connect. In some methods, there is a heating unit attached to the inkjet head or a separate carriage that fuses the parts receiving the fluid layer together. Methods that include this heating step can perform better than methods that do not include this heating step. Stronger parts are created because the polymer powders essentially melt together, rather than just stick together.
Thermal jet adhesives, such as multi-jet fusion, high-speed sintering and selective absorption fusion, are comparable to techniques that use lasers to melt polymer powders (called selective laser sintering), but are faster and provide better surface finishes, And it can reuse the powder left behind when the printer is running, a versatile technology that has applications in industries ranging from automotive to healthcare to consumer goods. Binder jetting variations that do not require heat can be filled with another material for increased strength, and these cold binder jetting processes also incorporate colored inks to produce multi-color parts for medical modeling and product prototyping. Once printed, the plastic parts are removed from the powder bed, cleaned, and ready for use without any further processing.
5.3 Sand Binder Jetting
Sand binder jetting is arguably the same technology compared to plastic binder jetting, but the printers and application scenarios are different enough to deserve a separate entry here, in fact the production of large sand casting molds, patterns and cores is One of the most common uses of binder jetting technology. The process is low-cost and fast, making it an excellent solution for foundries, where fine pattern designs that would be difficult or impossible to produce using traditional techniques can be printed in just a few hours.
Sand binder jet 3D printers can produce parts using sandstone or plaster. After printing, the core and mold are removed from the build area and cleaned to remove loose sand around them. The mold is usually immediately ready for casting. After casting, the mold is disassembled and the final metal part is removed.
6 Directional energy deposition
Directed Energy Deposition (DED) is a 3D printing process in which metallic materials are delivered and melted by powerful energy while being deposited. This is one of the broadest categories of 3D printing, depending on the form of the material (wire or powder) and energy The types (laser, electron beam, arc, supersonic, thermal, etc.) contain a long list of subcategories. Essentially, it’s a way that metal can be controlled deposited into layers (not extruded), and it has a lot in common with welding. The technology is used to build prints layer by layer, but more commonly it is used to repair metal objects or add functionality to existing metal parts by depositing material directly onto them, a process that is often followed by CNC machining to achieve better results. Tight tolerances. The use of DED in conjunction with CNC is so common that there is a sub-type of 3D printing called hybrid 3D printing.
Subcategories of DED can be divided based on feedstock type or energy type, and we chose to group them by energy type to highlight the difference that energy creates in the final product. When the materials used in this printing method are in powder form, the powder is often sprayed with an inert gas to reduce or eliminate the possibility of oxidation. For powder raw materials, a variety of powders can also be used to mix materials and obtain different results. The technology has been likened to robotic welding when the raw material is welding wire (a cheaper option), but it is much more complex.
Subtypes of directed energy deposition: powder laser energy deposition, wire arc additive manufacturing (WAAM), wire electron beam energy deposition, cold spray
Materials: Various metals, wire and powder forms
Dimensional accuracy: ±0.1mm
Common Applications: Restoration of high-end automotive/aerospace components, functional prototypes, and final parts
Advantages: High molding rate, ability to add metal to existing parts
Disadvantages: Inability to create complex shapes due to inability to create support structures, generally poor surface finish and accuracy
6.1 Laser directed energy deposition
Laser Directed Energy Deposition (L-DED), also known as Laser Metal Deposition (LMD) or Laser Engineered Net Shape (LENS), is a 3D printing technology that uses metal powder or wire fed through one or more nozzles and The passing strong laser melts the build platform or metal part. As the nozzle and laser move or the part moves on the multi-axis turntable, the object is built layer by layer. The build speed is faster than powder bed fusion, but This results in lower surface quality and significantly reduced accuracy, often requiring extensive post-processing.
Laser DED printers typically have sealed chambers filled with argon to avoid oxidation, and they can also operate with localized argon or nitrogen flows when processing less reactive metals. Commonly used metals for this technology include stainless steel, titanium and nickel alloys. This printing method is commonly used to repair high-end aerospace and automotive parts, such as jet engine blades, but is also used to produce entire components.
6.2 Electron beam directional energy deposition
Electron beam DED, also known as line electron beam energy deposition, is a 3D printing process that is very similar to laser DED. It is performed in a vacuum chamber and produces very clean, high-quality metal. As the wire is fed through one or more nozzles, it is melted by an electron beam. The layers are built individually. The electron beam forms A tiny molten pool into which the welding wire is fed by a wire feeder. When working with high-performance metals and reactive metals (such as alloys of copper, titanium, cobalt and nickel), electron beam is chosen for DED. Wire-fed DED using electron beams is faster than powder feeding. The process takes place in a vacuum chamber.
DED machines are virtually unlimited in terms of print size. For example, 3D printer manufacturer Sciaky has an EB DED machine that can produce parts nearly six meters long at speeds of 3 to 9 kilograms of material per hour. In fact, the electron beam DED is known as one of the fastest methods of manufacturing metal parts, although not the most accurate, which makes it ideal for the machining of large structures such as fuselages or replacement parts such as turbine blades.
6.3 Line directional energy deposition
Wire directed energy deposition, also known as wire arc additive manufacturing (WAAM), is a type of 3D printing that uses energy in the form of a plasma or wire arc to melt metal in the form of a wire, and then deposits the metal layer onto the printing device via a robotic arm superior. This method was chosen over similar techniques involving lasers or electron beams because it does not require a sealed chamber and can use the same metals (sometimes the exact same materials) as traditional welding.
Electrical energy deposition is considered the most cost-effective option among DED technologies because it can use existing arc welding robots and power sources, so the barrier to entry is relatively low. Unlike welding, the technology uses complex software to control the process. a range of variables, including thermal management of the robotic arm and tool paths.
There is no need to remove the support structure after printing, and the finished parts are typically CNC machined as needed to achieve tight tolerances, after which the printed parts are typically heat treated to eliminate residual stresses.
6.4 Cold spraying
Cold spray is a DED 3D printing technology that sprays metal powders at supersonic speeds to bond them together without melting them. There is almost no thermal stress, so there will be no thermal cracks or other problems caused by thermal stress. Common issues that may affect fusion technology. It has been used as a coating process since 2000, but recently, several companies have adopted cold spray for additive manufacturing because it can print with precise precision at speeds approximately 50 to 100 times higher than typical metal 3D printing. The geometry deposits metal up to several centimeters long, and the printer requires no inert gas or vacuum chamber.
Like other DED processes, cold spray does not produce prints with good surface quality or detail, but this is not always needed and the parts can be used immediately after printing.
6.5 Melting direct energy deposition
Fused direct energy deposition is a 3D printing process that uses heat to melt (or nearly melt) a metal (usually aluminum), which is then deposited layer by layer onto a build plate to form a 3D object. The technology differs from metal extrusion 3D printing in that the extruded version uses a raw metal material with a small amount of polymer inside to make the metal extrudable, and then removes the polymer in a heat treatment stage, while Molten DED uses pure metal. One can also liken molten or liquid DED to a material ejection, but the liquid metal typically flows from a nozzle rather than an array of nozzles where droplets are deposited.
The potential benefit of using heat to melt and then deposit metal is the ability to use less energy than other DED processes and the potential to use recycled metal directly as feedstock rather than wire or highly processed metal powder.
7 sheet lamination
Technically speaking, sheet lamination is a form of 3D printing, although it is quite different from the above mentioned techniques in that it functions to produce a 3D object by stacking or laminating very thin sheets of material together and then The final shape is formed by mechanical or laser cutting. Layers of material can be fused together using a variety of methods, depending on the material in question, which can range from paper to polymers to metals. When parts are laminated and then laser cut or machined into the desired shape, more waste is generated than with other 3D printing technologies.
Manufacturers use sheet lamination to produce cost-effective, non-functional prototypes at relatively high speeds. It is also a promising battery technology and can be used to produce composite items because the materials used can be printed on interchange in the process.
Types of 3D printing technologies: Laminated Object Manufacturing (LOM), Ultrasonic Consolidation (UC)
Materials: Paper, polymers and sheet metal
Dimensional accuracy: ±0.1mm
Common applications: non-functional prototypes, multi-color prints, casting molds.
Advantages: rapid production, composite printing
Disadvantages: low precision, more waste, some parts require post-production work
7.1 Laminated Additive Manufacturing
Lamination involves laminating pieces of material together and holding them together using glue, then using a knife (or laser or CNC mill) to cut the layered object into the correct shape. The technology is less common today as the cost of other 3D printing technologies has fallen while the size, speed and ease of use of 3D printers have increased dramatically in other technology categories.
7.1.1 Viscolithography Manufacturing (VLM)
VLM is a patented 3D printing process by BCN3D that laminates a thin layer of high-viscosity photosensitive resin onto a transparent transfer film. The mechanical system allows resin to be laminated from both sides of the film, allowing different resins to be combined to obtain multi-material parts and easily removable support structures. This technology has not yet been put into commercial application and may also be one of the resin 3D printing technologies.
7.1.2 Composite-based additive manufacturing (CBAM)
Startup Impossible Objects patented the technology, which fuses mats of carbon, glass or Kevlar with thermoplastic to create parts.
7.1.3 Selective Laminated Composite Object Manufacturing (SLCOM)
EnvisionTEC (now ETEC, part of Desktop Metal) developed the technology in 2016, which uses thermoplastics as the base material and woven fiber composites.
The above is our comprehensive summary of the seven major types of 3D printing. This article does not cover all the seven major categories of 3D printing.
