7 Most Common Types Of Additive Manufacturing Technologies In 3D Printing

Introduction

Many laymen think that 3D printing is just squeezing materials out of a hot nozzle and stacking them into shapes, but in fact, 3D printing is much more than that! Today, Antarctic Bear will introduce seven major types of 3D printing processes, and even 3D printing novices can clearly distinguish different 3D printing processes.

In fact, 3D printing, also known as additive manufacturing, is an umbrella term that covers several very different 3D printing processes. These technologies are worlds apart, but the key processes are the same. For example, all 3D printing starts with a digital model because the technology is digital in nature. The part or product is initially designed using computer-aided design (CAD) software or as an electronic file obtained from a digital parts library. The design file is then broken down into slices or layers for 3D printing by special build preparation software, which generates path instructions for the 3D printer to follow. Next you’ll learn the differences between these technologies and the typical uses of each.

Why 7 types?

Types of additive manufacturing can be divided according to the products they produce or the types of materials they use, and the International Standards Organization (ISO) divides them into seven general types (but these seven 3D printing categories also make it difficult to cover the increasing number of technical subtypes and hybrid technologies). :

● Material extrusion
● Reductive polymerization
● Powder bed fusion
● Material jetting
● Binder jetting
● Directed energy deposition
● Sheet lamination

I. Material extrusion

Material extrusion is exactly what it sounds like: material is extruded through a nozzle. Typically, the material is a plastic filament that is melted and extruded through a heated nozzle. The printer places the material on the build platform along a process path derived from the software. The filament then cools and solidifies to form a solid object. This is the most common form of 3D printing. It sounds simple at first glance, but it is actually a very broad category considering the materials that are extruded, including plastics, metals, concrete, biogels, and various foods. This type of 3D printer can range in price from $100 to seven figures.

●Subtypes of material extrusion: Fused deposition modeling (FDM), architectural 3D printing, micro 3D printing, bio 3D printing
●Materials: plastics, metals, 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 models, houses, etc.
●Advantages: Lowest-cost 3D printing method, wide range of materials
●Disadvantages: Usually lower material properties (strength, durability, etc.), usually low dimensional accuracy

1.Fused Deposition Modeling (FDM)

FDM 3D printers are a multi-billion dollar market with thousands of machines, ranging from basic models to complex models from manufacturers. FDM machines are called fused filament fabrication (FFF), which is exactly the same technology. Like all 3D printing technologies, FDM starts with a digital model, which is then converted into a path that the 3D printer can follow. With FDM, a filament (or a few at a time) on a spool is loaded into the 3D printer and then fed into the printer nozzle in the extruder head. The printer nozzle or nozzles are heated to the required temperature, which softens the filament so that successive layers can connect to form a solid part.

As the printer moves the extruder head along the specified coordinates on the XY plane, it continues to lay down the first layer. The extruder head then rises to the next height (the Z plane) and repeats the process of printing cross-sections, building layer by layer 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 are removed after printing. Some support structure materials can be dissolved in water or another solution.

2. 3D bioprinting

3D bioprinting, or bio3D printing, is an additive manufacturing process in which organic or biological materials (such as living cells and nutrients) are combined to create natural three-dimensional structures that resemble tissue. In other words, bioprinting is a type of 3D printing that can produce anything from bone tissue and 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. Essentially, 3D bioprinting works similarly to FDM 3D printing and belongs to the family of material extrusion. (Although extrusion is not the only bioprinting method)

3D bioprinting uses material (bio-ink) expelled from a needle to create the printed layers. These materials, called bio-inks, are primarily composed of living matter, such as cells in a carrier material – such as collagen, gelatin, hyaluronic acid, silk, alginate or nanocellulose, which acts as a molecular scaffold for structural growth and nutrients to provide support.

II. Reductive Polymerization

Vat polymerization (also known as resin 3D printing) is a family of 3D printing processes that uses a light source to selectively cure (or harden) photopolymer resin in a vat. In other words, light is precisely directed at 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 (depending on the printer) a small amount (usually between 0.01 and 0.05 mm) and the next layer is cured, connecting to the previous one. This process is repeated layer by layer until a 3D part is formed. After the 3D printing process is complete, the object is cleaned to remove the remaining liquid resin and post-cured (either in sunlight or in a UV chamber) to enhance the mechanical properties of the part.

The three most common forms of vat polymerization are stereolithography (SLA), digital light processing (DLP), and liquid crystal display (LCD), also known as mask stereolithography (MSLA). The fundamental difference between these types of 3D printing technologies lies in the light source and how it is used to cure the resin.

Some 3D printer manufacturers, especially those that make professional-grade 3D printers, have developed unique and patented variations of photopolymerization, so you may see different names for the technology on the market. Carbon, an industrial 3D printer manufacturer, uses a vat polymerization technology called Digital Light Synthesis (DLS), Stratasys’ Origin calls its technology Programmable Photopolymerization (P3), Formlabs offers its technology called Low Force Stereolithography (LFS), and Azul 3D was the first to commercialize vat polymerization in the form of Large Area Rapid Printing (HARP). There is also lithography-based metal manufacturing (LMM), projection microstereolithography (PμSL), and digital composite manufacturing (DCM), which is a filled photopolymer technology that introduces functional additives (such as metal and ceramic fibers) into the liquid resin.

● Types of 3D printing technology: Stereolithography (SLA), Liquid Crystal Display (LCD), Digital Light Processing (DLP), Micro Stereolithography (μSLA), etc.
● Materials: Photopolymer resins (castable, transparent, industrial, biocompatible, etc.)
● Dimensional accuracy: ±0.5% (lower limit is ±0.15 mm or 5 nm with μSLA)
● Common applications: Injection molded polymer prototypes and end-use parts, jewelry casting, dental applications, consumer products
● Advantages: Smooth surface finish, fine feature detail

1. Stereolithography (SLA)

SLA is the world’s first 3D printing technology. Stereolithography was invented in 1986 by Chuck Hull, who patented the technology and founded 3D Systems to commercialize it. Today, the technology is available to hobbyists and professionals from a wide range of 3D printer manufacturers. SLA uses a laser beam directed at a vat of resin to selectively cure cross-sections of the object within the print area, building up layer by layer. While most SLA printers use solid-state lasers to cure parts. One downside to this vat polymerization is that the point laser can take longer to trace across a cross-section of an object compared to our next method (DLP), which flashes light to harden an entire layer at once. Lasers, however, can produce more intense light, which is required for certain engineering-grade resins.

Microstereolithography (μSLA)

Microstereolithography can print microscopic parts with a resolution between 2 micrometers (μm) and 50 μm. For reference, the average width of a human hair is 75 μm. It is one of the “micro 3D printing” technologies. μSLA involves exposing a photosensitive material (liquid resin) to a UV laser. The difference lies in the specialized resin, the complexity of the laser, and the addition of lenses that create an almost unbelievably small spot of light.

Two-Photon Polymerization (TPP)

Another micro 3D printing technology, TPP (also known as 2PP) can be classified as SLA because it also uses lasers and photosensitive resins. It can print smaller parts than μSLA, down to 0.1 microns. TPP uses a pulsed femtosecond laser focused to a narrow spot in a vat of special resin. This spot is then used to solidify a single 3D pixel in the resin, also known as a voxel. These small voxels from nanometers to micrometers are solidified layer by layer in a predefined path. TPP is currently used for research, medical applications, and the manufacture of micro parts, such as micro electrodes and optical sensors.

2.Digital Light Processing (DLP)

DLP 3D printing uses a digital light projector (rather than a laser) to flash a single image of each layer (or multiple exposures for larger parts) simultaneously onto a layer or resin. DLP (more common than SLA) is used to produce larger parts or larger volumes of parts in a single batch because each layer exposure takes exactly the same amount of time regardless of how many parts are in the build, making it more efficient than the point laser method in SLA. The image of each layer is made up of square pixels, resulting in a layer formed of small rectangular blocks called voxels. Light is projected onto the resin using a light emitting diode (LED) screen or UV light source (lamp), which projects the light onto the build surface via a digital micromirror device (DMD).

Modern DLP projectors typically have thousands of micron-sized LEDs as light sources. Their on and off states are individually controlled, allowing for increased XY resolution. Not all DLP 3D printers are the same, the power of the light source, the lens it passes through, the quality of the DMD, and many other parts that make up a $300 machine can vary greatly compared to a $200,000+ machine.

Top-down DLP

Some DLP 3D printers have their light source mounted on the top of the printer, shining downward onto a vat of resin rather than upward. These “top-down” machines flash a layer of the image from the top, cure it one layer at a time, and then place the cured layer back into the vat. Each time the build plate is lowered, a recoater mounted on top of the vat moves back and forth over the resin to level out the new layer. Manufacturers say this approach produces a more stable part output for larger prints, since the printing process isn’t working against gravity. There is a limit to how much weight can be hung vertically from the build plate when printing bottom-up. The resin vat also supports the print as it prints, reducing the need for support structures.

Projection microstereolithography (PμSL)

As a unique type of vat polymerization in its own right, PμSL is classified as a subcategory of DLP. This is another micro 3D printing technology. PμSL uses ultraviolet light from a projector to cure specially formulated layers of resin at the micrometer scale (2 micrometer resolution and down to 5 micrometer layer height). This additive manufacturing technology is gaining momentum due to its low cost, accuracy, speed, and the range of materials it can work with, including polymers, biomaterials, and ceramics. It has shown potential for applications ranging from microfluidics and tissue engineering to micro-optics and biomedical micro-devices.

Lithography-based Metal Manufacturing (LMM)

Another distant cousin of DLP, this method of 3D printing using light and resin can create tiny metal parts for applications such as surgical tools and micromechanical parts. In LMM, metal powder is evenly dispersed in a photosensitive resin and then selectively polymerized by exposure to blue light through a projector. After printing, the polymer component of the green part is removed, leaving behind an all-metal, degreased part that is finished in a sintering process in a furnace. Raw materials include stainless steel, titanium, tungsten, brass, copper, silver, and gold.

3. Liquid Crystal Display (LCD)

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Liquid Crystal Display (LCD), also known as Mask Stereolithography (MSLA), is very similar to the above-mentioned DLP, 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. Like DLP, the LCD photomask is displayed digitally and consists 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 scaling of the lens, as is the case with DLP. Another difference between DLP’s printers and LCD technology is that the latter uses an array of hundreds of individual emitters instead of a single point emitting light source like a laser diode or DLP bulb.

Similar to DLP, LCD can achieve faster print times than SLA under certain conditions. This is because the entire layer is exposed at once, rather than tracing a cross-sectional area with a laser dot. Due to the low cost of LCD units, this technology has become the technology of choice in the field of low-priced desktop resin printers, but this does not mean that it has not been used professionally, and some industrial 3D printer manufacturers are pushing the limits of the technology with impressive results.

III. Powder Bed Fusion

Powder Bed Fusion (PBF) is a 3D printing process in which a source of thermal energy selectively melts powder particles (plastic, metal, or ceramic) within the build area to create a solid object layer by layer. A powder bed fusion 3D printer spreads a thin layer of powder material across the print bed, typically using a blade, roller, or wiper. Energy from the laser fuses specific points on the powder layer, and another powder layer is then deposited and fused to the previous layer. The process is repeated until the entire object is manufactured, with the final product surrounded and supported by the unfused powder.

PBF can produce parts with high mechanical properties (including strength, wear resistance and durability) for end-use applications in consumer goods, machinery and tools. 3D printers in this market segment are becoming increasingly affordable (starting at around $25,000), but it is considered an industrial technology.

● Types of 3D printing technology: Selective Laser Sintering (SLS), Laser Powder Bed Fusion (LPBF), Electron Beam Melting (EBM)
● Materials: Plastic powder, metal powder, ceramic powder
● Dimensional accuracy: ±0.3% (lower limit ±0.3mm)
● Common applications: functional parts, complex pipes (hollow design), small batch part production
● Advantages: functional parts, excellent mechanical properties, complex geometries
● Disadvantages: higher machine cost, usually high-cost materials, slower build speed

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. A very thin layer of powdered material (typically 0.1 mm thick) is then deposited onto the build platform using a recoating blade or wiper. The laser begins scanning the surface according to the pattern laid out in the digital model. The laser selectively sinters the powder and solidifies a cross section of the object. As the entire cross section is scanned, the build platform moves down in height by one layer thickness. The recoating blade deposits a new layer of powder over the most recently scanned layer, and the laser sinters the next cross section of the object onto the previously solidified cross section.

These steps are repeated until all objects have been manufactured. Unsintered powder remains in place to support the object, which 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 necessary. The parts can be polished, coated, or colored. There are many differentiating factors between 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 materials used in SLS 3D printing are nylons (PA6, PA12), but flexible parts can also be printed using TPU and other materials.

2.Micro Selective Laser Sintering (μSLS)

μSLS is a technology that belongs to SLS or Laser Powder Bed Fusion (LPBF) described below. It uses a laser to sinter powdered materials like SLS, but the material is usually metal instead of plastic, so it is more like LPBF. It is another micro 3D printing technology that can create parts with micro (less than 5 μm) 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 using a digital micromirror array is used to heat the nanoparticles and sinter them into the desired pattern. This set of steps is then repeated to build each layer of a 3D part in the μSLS system.

3. Laser Powder Bed Fusion (LPBF)

Of all the 3D printing technologies, this one has the most aliases. Officially known as laser powder bed fusion (LPBF), this metal 3D printing method is also widely referred to as direct metal laser sintering (DMLS) and selective laser melting (SLM). Early in the technology’s development, machine manufacturers created their own names for the same process, which are still used today. It is important to note that all three terms refer to the same process, even if some of the mechanical details differ. A

subtype of powder bed fusion, LPBF uses a bed of metal powder and one or more (up to 12) high-powered lasers. LPBF 3D printers use lasers to selectively fuse metal powder together on a molecular basis, layer by layer, until the model is complete. LPBF is a highly precise 3D printing method that is often used to create complex metal parts for aerospace, medical, and industrial applications.

Like SLS, LPBF 3D printers start with a digital model divided into slices. The printer loads powder into the build chamber and spreads it in thin layers onto the build plate with a scraper (like a windshield wiper) or roller. A laser traces the layers onto the powder. The build platform then moves down, applying another layer of powder and fusing it with the first layer until the entire object is built. The build chamber is closed, sealed, and in many cases filled with an inert gas, such as a nitrogen or argon mixture, to ensure that the metal does not oxidize during the melting process and to help remove debris from the melting process. After printing, the part is removed from the powder bed, cleaned, and often subjected to a secondary heat treatment for stress relief. The remaining powder is recycled and reused.

Differentiating factors for LPBF 3D printers include the type, strength, and number of lasers. A small, compact LPBF printer might have a single 30-watt laser, while an industrial version might have twelve 1,000-watt lasers. LPBF machines use common engineering alloys, such as stainless steel, nickel superalloys, and titanium alloys. There are dozens of metals that can be used in the LPBF process.

4.Electron beam melting (EBM)

EBM, also known as electron beam powder bed fusion (EB PBF), 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 parts such as titanium orthopedic implants, turbine blades for jet engines, and copper coils.

Electron beams produce more energy and heat, which is required for certain metals and applications. And instead of an inert gas environment, EBM is performed in a vacuum chamber to prevent beam scattering. Build chamber temperatures can reach up to 1,000 °C, and even higher in some cases. Because the electron beam uses electromagnetic beam control, it can move faster than a laser and can even be split to expose multiple areas simultaneously.

One of the advantages of EBM over LPBF is its ability to process both conductive materials and reflective metals, such as copper. Another feature of EBM is the ability to nest or stack separate parts within each other in the build chamber, since they do not necessarily have to be attached to the build plate, which greatly increases volume output. Electron beams typically produce greater layer thicknesses and rougher surface features than lasers. Due to the high temperatures in the build chamber, EBM-printed parts may not require stress relief via post-print heat treatment

IV. Material Jetting

Material jetting is a 3D printing process in which tiny droplets of material are deposited and then cured or solidified on a build plate. Objects are built one layer at a time using droplets of photopolymers or wax that cure when exposed to light. The nature of the material jetting process allows different materials to be printed on the same object. One application of this technology is to create parts with multiple colors and textures.

● Types of 3D printing technologies: Material Jetting (MJ), Nanoparticle Jetting (NPJ)
● Materials: Photosensitive resins (standard, pouring, clear, high temperature), wax
● Dimensional accuracy: ±0.1 mm
● Common applications: Full-color product prototypes, injection mold-like prototypes, low-run injection molds, medical models, fashion
● Advantages: Textured surface finish, full color and multiple materials available
● Disadvantages: Limited materials, not suitable for mechanical parts requiring precision, cost more than other resin technologies used for visual purposes

1. Material Jetting (M-Jet)

Material jetting (M-Jet) of polymers 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 a layer is deposited and cured, the build platform is lowered one layer thicker and the process is repeated to build the 3D object. M-Jet combines the high precision of resin 3D printing with the speed of filament 3D printing (FDM) to create parts and prototypes with realistic colors and textures.

All material jetting 3D printing technologies are not exactly the same. There are differences between printer manufacturers and proprietary materials. M-Jet machines deposit build material from multiple rows of print heads in a line-by-line manner. This approach enables the printer to manufacture multiple objects in a single line without compromising build speed. As long as the model is properly arranged on the build platform and the space within each build line is optimized, M-Jet can produce parts faster than many other types of resin 3D printers.

Objects made with M-Jet require supports, which are printed simultaneously during the build process from a dissolvable material that is removed in the post-processing phase. M-Jet is one of the few 3D printing technologies that offers objects made from multi-material printing and in full color. There are no hobbyist versions of material jetting machines, these machines are more for professionals at automakers, industrial design firms, art studios, hospitals and all types of product manufacturers who want to create accurate prototypes to test concepts and bring products to market faster. Unlike vat polymerization techniques, M-Jet does not require post-curing, as the UV light in the printer fully cures each layer.

Aerosol

Jet is a unique technology developed by a company called Optomec, which is primarily used for 3D printing electronics. Components such as resistors, capacitors, antennas, sensors and thin-film transistors are printed using aerosol jet technology. It can be roughly likened to spray painting, but what distinguishes it from industrial coating processes is that it can be used to print complete 3D objects.

The electronic ink is placed in an atomizer, which produces droplets with a diameter between 1 and 5 microns. The aerosol mist is then delivered to the deposition head, focused by the sheath gas, which creates a high-speed particle spray. Since the entire process uses energy, the technology is sometimes also called directed energy deposition, but since the material is in droplet form in this case, we include it in material jetting.

Plastic Freeforming

The German company Arburg has created a technology called Plastic Freeforming (APF), which is a combination of extrusion technology and material jetting technology. It uses commercially available plastic granules, which are melted during the injection molding process and moved to a discharge unit. The high-frequency nozzle closing produces a rapid opening and closing movement of up to 200 small plastic droplets with a diameter of between 0.2 and 0.4 mm per second. The droplets combine with the hardening material as they cool. Generally, no post-processing is required. If support material is used, it must be removed.

2.Nanoparticle Jetting (NPJ)

NanoParticle Jetting (NPJ) is one of the few proprietary technologies that is difficult to categorize. Developed by a company called XJet, it uses a printhead array with thousands of inkjet nozzles to simultaneously eject millions of ultrafine droplets of material onto a build tray in ultra-thin layers, while also ejecting support material at the same time. Metal or ceramic particles are suspended in a liquid. The process occurs at high temperatures, and the liquid evaporates during jetting, leaving mostly only the metal or ceramic material. The resulting 3D part has only a small amount of binder remaining, which is removed in a post-sintering process.

V. Binder Jetting

Binder jetting is a 3D printing process in which a liquid binder selectively binds areas of a layer of powder. This technology type has features of both powder bed fusion and material jetting. Similar to PBF, binder jetting uses powdered materials (metal, plastic, ceramic, wood, sugar, etc.), and like material jetting, a liquid binder polymer is deposited from an inkjet. Whether it is metal, plastic, sand, or another powdered material, the binder jetting process is the same.

First, a recoating blade spreads a thin layer of powder on the build platform. Then, a print head with an inkjet nozzle passes over the bed, selectively depositing droplets of binder to bind the powder particles together. Once the layer is complete, the build platform moves down and the blade recoats the surface. The process is then repeated until the entire part is complete.

Binder jetting is unique in that there is no heat during the printing process. The binder acts as a glue that holds the polymer powder together. After printing, the part is encased in unused powder and is usually left to cure. The part is then removed from the powder bin, and the excess powder is collected and can be reused. From here, post-processing is required depending on the material, with the exception of sand, which can usually be used as a core or mold directly out of the printer. When the powder is metal or ceramic, post-processing involving heating melts away the binder, leaving only the metal. Plastic part post-processing often includes coatings to improve the surface finish. You can also polish, paint, and sand polymer binder jetted parts.

Binder jetting is fast and has high productivity, so it can produce large quantities of parts more cost-effectively than other AM methods. Metal binder jetting can be used on a variety of metals and is popular for end-use consumer products, tooling, and volume spare parts. However, polymer binder jetting has limited material selection and produces parts with lower structural properties. Its value lies in the ability to produce full-color prototypes and models.

●Subtypes of 3D Printing Technology: Metal Binder Jetting, Polymer Binder Jetting, Sand Binder Jetting
●Materials: Sand, polymer, metal, ceramic, etc.
●Dimensional accuracy: ±0.2 mm (metal) or ±0.3 mm (sand)
●Common applications: functional metal parts, full-color models, sand castings and molds
●Advantages: low cost, large build volume, functional metal parts, excellent color reproduction, fast printing speed, support-free design flexibility
●Disadvantages: multi-step process for metals, polymer parts are not durable

1.Metal Binder Jetting

Binder Jetting can also be used to create solid metal objects with complex geometries that are far beyond the capabilities of traditional manufacturing techniques. Metal binder jetting is a very attractive technology for mass production of metal parts and achieving lightweighting. Because binder jetting can print parts with complex pattern fills rather than solid bodies, the resulting parts are significantly lighter in weight, yet their strength remains the same. The porosity characteristics of binder jetting can also be used to achieve lighter end parts for medical applications, such as implants.

Overall, the material properties of metal binder jetted parts are comparable to those of metal parts produced by metal injection molding, one of the most widely used manufacturing methods for mass production of metal parts. In addition, binder jetted parts exhibit increased surface smoothness, especially in internal channels.

Metal binder jet parts require secondary processing after printing to achieve good mechanical properties. Fresh out of the printer, the parts are essentially composed of metal particles bound together with a polymer binder. These so-called “green parts” are brittle and cannot be used as is. After the printed parts are removed from the metal powder bed (a process called de-powdering), they are heat treated in a furnace (a process called sintering). Both printing parameters and sintering parameters are tuned for the specific part geometry, material, and desired density. Bronze or other metals are sometimes used to infiltrate the voids in the binder jet part, thereby achieving zero porosity.

2. Plastic Binder Jetting

Plastic binder jetting is a process very similar to metal binder jetting in that it also uses powder and liquid binders, but the applications are very different. Once printed, the plastic part is removed from its powder bed and cleaned and typically ready for use without further processing, but these parts lack the strength and durability found in 3D printing processes. Plastic binder jetted parts can be filled with another material for added strength. Binder jetting with polymers is known for its ability to produce multi-color parts for medical modeling and product prototyping.

3.Sand binder jetting

Sand binder jetting differs from plastic binder jetting in the printer and printing process, so it is distinguished here. Producing large sand casting molds, patterns and cores is one of the most common uses of binder jetting technology. The low cost and speed of the process make it an excellent solution for foundries, as it is difficult to produce fine pattern designs in a few hours using traditional technologies.

The future of industrial development continues to place high demands on foundries and suppliers. Sand 3D printing is at the beginning of its potential. After printing, the printer needs to remove the cores and molds from the build area and clean them to remove any loose sand. The mold can usually be ready for casting immediately. After casting, the mold is disassembled and the final metal part is removed.

4.Multi Jet Fusion (MJF)

Another unique and brand-specific 3D printing process that doesn’t easily fit into any existing categories, and isn’t actually binder jetting, is HP’s Multi Jet Fusion. MJF is a polymer 3D printing technology that uses a powdered material, a liquid fusing material, and a detailing agent. The reason it isn’t considered binder jetting is that heat is added to the process, which produces parts with greater strength and durability, and the liquid isn’t exactly a binder. The process gets its name from the multiple inkjet heads that perform the printing process.

During the Multi Jet Fusion printing process, the printer lays down a layer of material powder, usually nylon, on the print bed. After this, the inkjet heads move through the powder and deposit the fusing agent and detailing agent on top of it. An infrared heating unit then moves over the print. Wherever the fusing agent was added, the underlying layer melts together, while the areas with detailing agent remain powdery. The powdery parts fall away, producing the desired geometry. This also eliminates the need for modeling supports, as the underlying layers support the layers printed on top of them. To complete the printing process, the entire powder bed, along with the printed part in it, is moved to a separate processing station, where much of the loose, unmelted powder is vacuumed out and can be reused.

Multi Jet Fusion is a versatile technology that has been used in a variety of industries including automotive, healthcare and consumer products.

VI.Powder Directed Energy Deposition

Directed Energy Deposition (DED) is a 3D printing process in which metal materials are fed and melted by powerful energy while being deposited. This is one of the broadest categories of 3D printing, with many subcategories depending on the form of the material (wire or powder) and the type of energy (laser, electron beam, arc, supersonic, heat, etc.). Essentially, it has a lot in common with welding.

The technology is used for layer-by-layer printing, often followed by CNC machining to achieve tighter tolerances. The use of DED in conjunction with CNC is so common that there is a subtype of 3D printing called hybrid 3D printing, a hybrid 3D printer that contains DED and CNC units in the same machine. The technology is considered a faster and cheaper alternative for small batches of metal castings and forgings, as well as critical repairs for applications in the offshore oil and gas industry and aerospace, power generation and utilities industries.

● Subtypes of Directed Energy Deposition: Powder Laser Energy Deposition, Wire Arc Additive Manufacturing (WAAM), Wire Electron Beam Energy Deposition, Cold Spray
● Materials: Various metals, in wire and powder form
● Dimensional accuracy: ±0.1 mm
● Common applications: Repair of high-end automotive/aerospace parts, functional prototypes and final parts
● Advantages: High build-up rates, ability to add metal to existing components
● Disadvantages: Inability to make complex shapes due to inability to make support structures, typically poor surface finish and accuracy

1.Laser Directed Energy Deposition

Laser Directed Energy Deposition (L-DED), also known as Laser Metal Deposition (LMD) or Laser Engineered Net Shaping (LENS), uses metal powder or wire fed through one or more nozzles and melted onto a build platform or metal part by a powerful laser. The object is built up layer by layer as the nozzle and laser move or the part moves on a multi-axis turntable. Build speeds are faster than powder bed fusion, but result in lower surface quality and significantly reduced accuracy, often requiring extensive post-processing. Laser DED printers typically have a sealed chamber filled with argon to avoid oxidation. They can also operate with only a localized atmosphere of argon or nitrogen when processing less reactive metals.

Common metals used in the process include stainless steel, titanium, and nickel alloys. This printing method is often used to repair high-end aerospace and automotive parts, such as jet engine blades, but is also used to produce entire parts.

2. Electron beam directed energy deposition

Electron beam DED, also known as wire electron beam energy deposition, is a 3D printing process very similar to laser DED. It is carried out in a vacuum chamber and can produce very clean, high-quality metal. As a wire passes through one or more nozzles, it is melted by the electron beam. Layers are built up individually, with the electron beam forming a tiny molten pool into which the wire is fed by a wire feeder. Electron beam is chosen for DED when processing high-performance metals and reactive metals such as copper, titanium, cobalt, and nickel alloys.

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 6 meters long at a rate of 3 to 9 kilograms of material per hour. Electron beam DED is touted as one of the fastest ways to make metal parts, although not the most precise, making it an ideal processing technology for building large structures such as fuselages or replacement parts such as turbine blades.

3. Wire-controlled 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 plasma or electric arcs to melt metal in wire form and deposit the metal layer by layer onto a surface, such as a multi-axis turntable, by a robotic arm to form a shape. This method was chosen over similar technologies that use 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 direct energy deposition is considered the most cost-effective option among DED technologies and can use existing arc welding robots and power supplies, so the barrier to entry is relatively low. But unlike welding, this technology uses complex software to control a range of variables in the process, including thermal management of the robotic arm and tool paths. This technology has no support structures to remove, and the finished parts are usually CNC machined to achieve tight tolerances or surface finishes when necessary.

4. Cold spray

Cold spray is a DED 3D printing technology that sprays metal powders at supersonic speeds to bond them without melting and with virtually no thermal cracking or thermal stresses. It has been used as a coating process since the early 2000s, but more recently, several companies have turned to cold spray for additive manufacturing because it can print at speeds 50 to 100 times higher than typical metal 3D processes and does not require an inert gas or vacuum chamber.

Like all DED processes, cold spray does not produce prints with great surface quality or detail, but parts can be used directly from the print bed.

5. Melted Direct Energy Deposition

Molten direct energy deposition is a 3D printing process that uses heat to melt metal (usually aluminum) and then deposits it layer by layer onto a build plate to form a 3D object. The technology differs from metal extrusion 3D printing in that extrusion uses a metal feedstock that has a small amount of polymer inside, making the metal extrudable. The polymer is then removed during a heat treatment stage, while molten DED uses pure metal. One can also liken molten or liquid DED to material jetting, but instead of a series of nozzles depositing droplets, liquid metal typically flows out of a nozzle.

Variants of this technology are being developed, and molten metal 3D printers are rare. The benefit of using heat to melt and then deposit the metal is the ability to use less energy than other DED processes and potentially use recycled metal directly as a feedstock, rather than filaments or highly processed metal powders.

VII. Sheet Lamination

Sheet lamination is technically a form of 3D printing and is very different from the above techniques. It functions by stacking and laminating very thin sheets of material together to produce a 3D object or stack, which is then cut mechanically or by laser to form the final shape. The layers of material can be fused together using a variety of methods, including heat and sound, depending on the material, 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 other 3D printing techniques.

Manufacturers use sheet lamination to produce cost-effective non-functional prototypes at relatively high speeds, which can be used in battery technology and to produce composite materials because the materials used can be interchanged during the printing process.

● Types of 3D printing technology: Laminated Object Manufacturing (LOM), Ultrasonic Consolidation (UC)
● Materials: Paper, polymers and sheet metal
● Dimensional accuracy: ±0.1 mm
● Common applications: Non-functional prototypes, multi-color printing, casting.
● Advantages: Can be produced quickly, composite printing
● Disadvantages: Low accuracy, high waste, some parts require post-production

Laminated Additive Manufacturing

Lamination is a 3D printing technique where sheets of material are layered together and bonded together using glue, and then a knife (or laser or CNC router) is used to cut the layered object into the correct shape. This technique is less common today as other 3D printing techniques have dropped in cost and increased in speed and ease of use.

Viscous Lithography Manufacturing (VLM): VLM is BCN3D’s patented 3D printing process that laminates thin layers of high-viscosity photosensitive resins onto a transparent transfer film. A mechanical system allows the resin to be laminated from both sides of the film, making it possible to combine different resins to obtain multi-material parts and easily removable support structures. This technology has not yet been commercialized, but it can also be classified as one of the laminated 3D printing technologies. Composite

Based Additive Manufacturing (CBAM): Startup Impossible Objects has applied for a patent for this technology, which fuses carbon, glass or Kevlar mats with thermoplastics to make parts.

Selective Laminated Composite Manufacturing (SLCOM): EnvisionTEC, now known as ETEC, is owned by Desktop Metal and developed this technology in 2016, which uses thermoplastics as the base material and woven fiber composites.

Note: There are many types of 3D printing technologies. The above are the seven most common types of additive manufacturing technologies in 3D printing, and do not cover all 3D printing technologies on the market.