3D Printing

Many people think of 3D printing as extruding materials from a hot nozzle and stacking them into shapes, but 3D printing is actually much more than that!

In fact, 3D printing, also known as additive manufacturing, is an umbrella term that covers several distinct 3D printing processes. The 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 inherently digital. A part or product is initially designed using computer-aided design (CAD) software or an electronic file obtained from a digital parts library. The design file is then passed through special build preparation software that breaks it down into slices or layers for 3D printing, generating 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 fail to cover an increasing number of technologies. subtypes and hybrid technologies). :

• Material extrusion
• Restore aggregation
• Powder bed fusion
• Material jetting
• Binder jetting
• Directed energy deposition
• Sheet lamination

1.Material Extrusion

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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. This may sound simple at first, but it’s actually a very broad category considering the materials that are extruded, including plastics, metals, concrete, biogels, and various food products. Prices for this type of 3D printer range from $100 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 models, houses, etc.
• Advantages: Lowest cost 3D printing method, wide range of materials
• Disadvantages: Usually the material properties are low (strength, durability, etc.), and the dimensional accuracy is usually not high

Fused Deposition Modeling (FDM)

FDM 3D printers are a multi-billion dollar market with thousands of machines ranging from basic models to manufacturers’ sophisticated models. The FDM machine is called Fused Filament Fabrication (FFF), which is the exact same technology. Like all 3D printing technologies, FDM starts with a digital model and then converts it into a path that the 3D printer can follow. With FDM, a spool of filament (or a few at a time) is loaded into the 3D printer and fed into the printer nozzle in the extrusion head. The printer nozzle or nozzles are heated to the desired temperature, softening the filament so that successive layers join together to form a solid part.

As the printer moves the extrusion head along the specified coordinates on the XY plane, it continues to lay down the first layer. The extrusion head then rises to the next height (the Z plane) and the process of printing the cross-section is repeated, 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.

3D bioprinting

3D bioprinting, or 3D bioprinting, is an additive manufacturing process in which organic or biological materials, such as living cells and nutrients, are combined to create natural, tissue-like three-dimensional structures. 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 (bioink) expelled from a needle to create printed layers. These materials, known as bioinks, are primarily composed of living substances, such as cells in a carrier material – such as collagen, gelatin, hyaluronic acid, silk, alginate or nanocellulose, molecules that act as structural growth and nutrients Bracket to provide support.

Architectural 3D printing

Architectural 3D printing is a rapidly growing field of material extrusion. The technology involves using very large 3D printers, often tens of meters tall, to extrude building materials such as concrete from nozzles. These machines usually come in the form of gantry or robotic arm systems. 3D architectural printing technology is now used in homes, architectural features, and construction projects from wells to walls. Researchers say it has the potential to significantly change the entire construction industry because it reduces labor requirements and reduces construction waste.

There are dozens of 3D-printed homes 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 is also gaining attention as a more sustainable construction method.

2. Reduction and polymerization

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Barrel polymerization (also known as resin 3D printing) is a family of 3D printing processes that use a light source to selectively cure (or harden) a photopolymer resin in a barrel. In other words, the light is directed precisely at specific points or areas of the liquid plastic to harden it. After the first layer has cured, the build platform will move up or down (depending on the printer) a small amount (usually between 0.01 and 0.05 mm) and the next layer cures, joining the previous layer. 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 remaining liquid resin and post-cured (in sunlight or in a UV chamber) to enhance the mechanical properties of the part.

The three most common forms of barrel aggregation 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 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 variants of photopolymerization, so you may see different names for the technology on the market. Carbon, an industrial 3D printer maker, uses a barrel polymerization technology called digital light synthesis (DLS), Stratasys’ Origin calls its technology programmable photopolymerization (P3), and Formlabs offers what it calls low-force stereolithography (LFS). technology, and Azul 3D is the first to commercialize vat aggregation in the form of Large Area Rapid Printing (HARP). There is also photolithography-based metal fabrication (LMM), projected microstereolithography (PμSL), and digital composite manufacturing (DCM), a filled photopolymer technology that incorporates functional additives such as metal and ceramic fibers ) introduced 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 is ±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 finish, fine feature details

Stereolithography (SLA)

Microstereolithography can print microscopic parts with resolutions between 2 micrometers (μm) and 50 μm. For reference, the average width of a human hair is 75 microns. 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 almost unbelievably small spots of light.

Another micro-3D printing technology, TPP (also known as 2PP), can be classified as SLA because it also uses laser and photosensitive resin, and it can print smaller parts than μSLA, as small as 0.1 micron. TPP uses a pulsed femtosecond laser focused to a narrow spot in a vat of special resin. This spot is then used to cure individual 3D pixels, also known as voxels, in the resin. By sequentially solidifying these small nano- to micron-scale voxels layer by layer in a predefined path. TPP is currently used in research, medical applications and the manufacture of microscopic parts such as microelectrodes and optical sensors.

DLP 3D printing uses a digital light projector (rather than a laser) to simultaneously flash a single image of each layer (or multiple exposures for larger parts) on a layer or resin. DLP (more common than SLA) is used to produce larger parts or higher volume parts in a single batch because each layer of exposure takes exactly the same amount of time no matter how many parts are in the build, compared to the point in SLA Laser methods are more efficient. Each layer’s image is made up of square pixels, resulting in a layer being formed from small rectangular blocks called voxels. Light is projected onto the resin using a light-emitting diode (LED) screen or UV light source (lamp), and 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/off status is controlled individually to improve 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 the many other parts that make up a $300 machine can all differ greatly from one that costs over $200,000 compared to.

Top-down DLP

Some DLP 3D printers have a light source mounted on top of the printer that shines down onto the resin barrel rather than up. These “top-down” machines flash an image from the top, cure it one layer at a time, and then return the cured layer to 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 the new layer. The manufacturer says this method produces a more stable part output for larger prints because the printing process does not fight gravity. When printing from the bottom up, there is a limit to how much weight can be hung vertically from the build plate. The resin barrel also supports the print while printing, reducing the need for support structures.

Being a distinct type of barrel aggregation in its own right places PμSL into a subcategory of DLP. This is another micro 3D printing technology. PμSL uses UV light from a projector to cure layers of specially formulated resin at the micron scale (2 micron resolution and layer heights as low as 5 microns). This additive manufacturing technology continues to evolve due to its low cost, accuracy, speed, and range of materials that can be used, including polymers, biomaterials, and ceramics. It has shown potential for applications ranging from microfluidics and tissue engineering to micro-optics and biomedical microdevices.

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 micromachined parts. In LMM, metal powders are uniformly dispersed in a photosensitive resin and then selectively polymerized by exposure to blue light through a projector. After printing, the polymer components of the green parts are removed, leaving fully metal, degreased parts that are completed during a sintering process in a furnace. Raw materials include stainless steel, titanium, tungsten, brass, copper, silver and gold.

Liquid crystal display (LCD)

Like 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 the cross-sectional area with a laser spot. 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 is not used professionally, and some industrial 3D printer manufacturers are pushing the limits of technology and achieving impressive results. .

3.Powder bed fusion

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Powder bed fusion (PBF) is a 3D printing process in which thermal energy 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 spread a thin layer of powdered material over the print bed, typically using a type of blade, roller, or wiper. The energy from the laser fuses specific points on the powder layer, then another powder layer is deposited and fused to the previous layer. The process is repeated until the entire object is manufactured, with the final product being wrapped and supported by unfused powder.

PBF enables the manufacture of parts with high mechanical properties, including strength, wear resistance and durability, for end-use applications in consumer products, machinery and tools. 3D printers in this segment are getting cheaper (starting at around $25,000), but it is considered an industrial technology.

• Types of 3D printing technologies: Selective Laser Sintering (SLS), Laser Powder Bed Melting (LPBF), Electron Beam Melting (EBM)
• Material: plastic powder, metal powder, ceramic powder
• Dimensional accuracy: ±0.3% (lower limit ±0.3mm)
• Common applications: functional components, complex pipes (hollow design), small batch component production
• Advantages: functional components, excellent mechanical properties, complex geometries
• Disadvantages: Higher machine costs, often high-cost materials, slower construction speeds

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 powder material (typically 0.1mm thick) is then deposited onto the build platform using a recoat 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 cross-sections of the object. As the entire cross section is scanned, the build platform moves down one thickness in height. The recoat blade deposits a new layer of powder on top of the most recently scanned layer, and the laser sinters the next cross-section of the object onto the previously solidified cross-section.

Repeat these steps until all objects are made. The unsintered powder remains in place to support the object, which reduces or eliminates the need for support structures. Once the parts are removed from the powder bed and cleaned, no other post-processing steps are necessary. Parts can be polished, coated or stained. 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 nylon (PA6, PA12), but flexible parts can also be printed using TPU and other materials.

Micro-selective laser sintering (μSLS)

μSLS belongs to the technology of SLS or Laser Powder Bed Fusion (LPBF) described below. It uses a laser to sinter a powdered material, such as SLS, but this material is typically metal rather than plastic, so it’s more like LPBF. It is another micro-3D printing technology that can create parts at microscopic (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 the 3D part in the μSLS system.

Laser powder bed fusion (LPBF)

Of all 3D printing technologies, this one has the most aliases. Formally known as laser powder bed fusion (LPBF), this method of metal 3D printing is also widely known as direct metal laser sintering (DMLS) and selective laser melting (SLM). Early in the development of this technology, machine builders created their own names for the same processes, and these names are still used today. In particular, these three terms refer to the same process, even if some mechanical details differ.

A subtype of powder bed fusion, LPBF uses a metal powder bed and one or more (up to 12) high-power lasers. LPBF 3D printers use lasers to selectively fuse metal powders together layer by layer on a molecular basis until the model is complete. LPBF is a highly precise 3D printing method commonly 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 the powder into the build chamber and then spreads it into a thin layer on the build plate using a scraper (like a windshield wiper) or a roller. The laser traces the layers onto the powder. The build platform then moves down and another layer of powder is applied and blended with the first layer until the entire object is constructed. 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, parts are removed from the powder bed, cleaned, and often subjected to a secondary heat treatment to relieve stress. The remaining powder is recycled and reused.

Differentiating factors for LPBF 3D printers include the type, intensity, and number of lasers. A small compact LPBF printer might have one 30-watt laser, while an industrial version might have 12 1,000-watt lasers. LPBF machines use common engineering alloys such as stainless steel, nickel superalloys and titanium alloys. There are dozens of metals available for use in the LPBF process.

EBM, also known as electron beam powder bed fusion (EB PBF), is a metal 3D printing and rapid prototyping 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, jet engine turbine blades and copper coils.

Electron beams produce more energy and heat, which is needed for some metals and applications. Moreover, EBM is not carried out in an inert gas environment but in a vacuum chamber to prevent beam scattering. Build chamber temperatures can reach up to 1,000 °C, and in some cases even higher. Because the electron beam is steered using an electromagnetic beam, it can move faster 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 the 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 volumetric output. Compared to lasers, electron beams typically produce greater layer thicknesses and rougher surface features. Due to high temperatures in the build chamber, EBM printed parts may not require post-print heat treatment to relieve stress.

4. Material injection

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Material jetting is a 3D printing process in which tiny droplets of material are deposited and then solidified, or solidified, on the build plate. Objects are built 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. One application of this technology is to create parts in a variety of colors and textures.

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

Material Jetting (M-Jet)

Material jetting of polymers (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 solidified, the build platform lowers the layer thickness 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 jet 3D printing technologies are not identical. There are differences between printer manufacturers and proprietary materials. The M-Jet machine deposits build material from multiple rows of print heads in a line-by-line fashion. This approach enables the printer to manufacture multiple objects in a single line without affecting build speed. As long as the model is properly aligned on the build platform and the space within each build line is optimized, the M-Jet can produce parts faster than many other types of resin 3D printers.

Objects made with M-Jet require supports, which are simultaneously printed during the build process from a dissolvable material that is removed in a post-processing stage. M-Jet is one of the few 3D printing technologies that offers objects made from multi-material printing and full color. There is no hobbyist version of material jetting machines, these machines are more suitable for professionals at automotive manufacturers, industrial design firms, art studios, hospitals and all types of product manufacturers who want to create accurate prototypes to test concepts and more quickly Bring products to market. Unlike barrel polymerization technology, M-Jet requires no post-cure as UV light in the printer fully cures each layer.

Aerosol jet

Aerosol Jet is a unique technology developed by a company called Optomec, primarily 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 compared to spray paint, but what sets it apart from industrial coating processes is that it can be used to print complete 3D objects.

E-ink is placed into an atomizer, which produces droplets between 1 and 5 microns in diameter. The aerosol mist is then transported to the deposition head and focused by the sheath gas, thereby producing a high-speed particle spray. Because of the energy used throughout the process, this technique is sometimes called directed energy deposition, but since the material is in the form of droplets in this case, we include it within material ejection.

Plastic freeforming

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

2. Nanoparticle Jet (NPJ)

NanoParticle Jetting (NPJ) is one of the few proprietary technologies that is difficult to classify. Developed by a company called XJet, it uses an array of printheads with thousands of inkjet nozzles to simultaneously print millions of Ultra-fine droplets of material are ejected onto an ultra-thin layer of build pallets, simultaneously ejecting support material. Metal or ceramic particles are suspended in a liquid. The process occurs at high temperatures, and the liquid evaporates as it is sprayed, leaving mostly only the metal or ceramic material. The resulting 3D part retains only a small amount of binder, which is removed in the post-sintering process.

5. Adhesive spraying

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Binder jetting is a 3D printing process in which a liquid adhesive selectively bonds areas of a layer of powder. This technology type combines the characteristics of powder bed fusion and material ejection. Like PBF, binder jetting uses powdered materials (metals, plastics, ceramics, wood, sugar, etc.), and like material jetting, a liquid binder polymer is deposited from an inkjet. Whether it is metal, plastic, sand or other powdered materials, the binder jetting process is the same.

First, recoat the blade by applying a thin layer of powder to the build platform. A printhead with an inkjet nozzle then passes over the bed, selectively depositing droplets of adhesive to bind the powder particles together. After the layer is complete, the build platform moves down and the blade recoats the surface. Then repeat the process until the entire section is complete.

Binder jetting is unique in that there is no heat during the printing process. The binder acts as the glue that holds the polymer powder together. After printing, the parts are encased in unused powder, which is usually left to cure. The part is then removed from the powder bin, 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 often be used as a core or mold directly from the printer. When the powder is metal or ceramic, post-processing involving heat melts away the binder, leaving only the metal. Plastic part post-processing often includes coatings to improve surface finish. You can also polish, paint and sand polymer adhesive sprayed parts.

Binder jetting is fast and productive, so it can produce high volumes of parts more cost-effectively than other AM methods. Metal binder jetting can be used on a variety of metals and is popular in end-use consumer goods, tools and bulk spare parts. However, polymer binder jetting has limited material options 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
• ●Material: 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 print speeds, support-free design flexibility
• ●Disadvantages: A multi-step process for metal, polymer parts are not durable

Metal adhesive jetting

Binder Jetting can also be used to create solid metal objects with complex geometries that are well beyond the capabilities of traditional manufacturing techniques. Metal binder jetting is a very attractive technology for mass production and lightweighting of metal parts. Because binder jetting can print parts with complex pattern infills instead of solid bodies, the resulting parts are significantly lighter but remain as strong. The porosity characteristics of adhesive 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 produced by metal injection molding and is one of the most widely used manufacturing methods for the 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. Fresh off the printer, the part essentially consists of metal particles held together with a polymer adhesive. These so-called “green parts” are fragile and cannot be used as is. After the printed parts are removed from the metal powder bed (a process called depowdering), they are heat treated in a furnace (a process called sintering). Both printing and sintering parameters are tuned for the specific part geometry, material and desired density. Bronze or other metals are sometimes used to penetrate the voids in adhesive-blasted parts, thereby achieving zero porosity.

Plastic adhesive spraying

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

Sand binder spraying

Sand binder jetting has different printers and printing processes than plastic binder jetting, so they will be distinguished here. The production of 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 matter of hours using traditional techniques.

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 will need to remove the core and mold from the build area and clean them to remove any loose sand. The mold is usually ready for casting immediately. After casting, the mold is disassembled and the final metal parts are removed.

Multiple jet fusion (MJF)

Another unique and brand-specific 3D printing process that doesn’t easily fit into any existing category, and isn’t actually binder jetting, is HP’s Multi Jet Fusion. MJF is a polymer 3D printing technology that uses powder materials, liquid fusion materials, and refiners. The reason it’s not considered adhesive jetting is that heat is added to the process, which results in a stronger and more durable part, and the liquid isn’t exactly an adhesive. 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 head passes through the powder and deposits melting and refining agents on it. The infrared heating device then moves over the print. Wherever you add flux, the underlying layers melt together while the areas with the refiner remain powdery. The powdery parts fall off, creating the desired geometry. This also eliminates the need for modeling support, as the underlying layers support the layers printed above them. To complete the printing process, the entire powder bed and the printed parts within it are moved to a separate processing station, where most of the loose, unmelted powder is evacuated and can be reused.

Multi Jet Fusion is a versatile technology that has found applications in multiple industries including automotive, healthcare and consumer goods.

6. Powder directional energy deposition

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

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

△DED metal 3D printing technology can quickly create a strong metal part that can then be machined to tight tolerances

• 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: ±0.1 mm
• Common applications: Repair of high-end automotive/aerospace components, functional prototypes and final parts
• Advantages: High stacking rate, ability to add metal to existing components
• Disadvantages: Unable to make complex shapes due to inability to make support structures, usually poor surface finish and accuracy

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 sent through one or more nozzles and melted by a powerful laser to build the platform or on metal parts. Objects are deposited layer by layer as the nozzle and laser move or the part moves on a multi-axis turntable. Build speed is faster than powder bed fusion, but results in lower surface quality and significantly less accuracy, often requiring extensive post-processing. Laser DED printers typically have a sealed chamber filled with argon gas to avoid oxidation. They can also operate using only localized argon or nitrogen when working with less reactive metals.

Commonly used metals in this process 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.

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’s done in a vacuum chamber and produces very clean, high-quality metal. As a wire passes through one or more nozzles, it is melted by the electron beam. The layers are built individually, with an electron beam forming a tiny molten pool into which welding wire is fed by a wire feeder. Electron beams are chosen for DED when working with 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 methods of manufacturing metal parts, although not the most accurate, making it an ideal machining technology for building large structures such as fuselages or replacement parts such as turbine blades.

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 a plasma or arc to melt metal in the form of a wire and deposit the metal layer by layer via a robotic arm. A surface, such as a multi-axis turntable, forms a shape. This method was chosen over similar technologies such as laser or electron beam 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 sources, so the barrier to entry is relatively low. But unlike welding, this technology uses sophisticated software to control a range of variables in the process, including thermal management of the robotic arm and tool paths. There are no support structures to remove with this technology, and the finished part is typically CNC machined to tight tolerances or surface polished where necessary.

Cold spraying

Cold spray is a DED 3D printing technology that sprays metal powders at supersonic speeds to bond them without melting and creating virtually no thermal cracking or thermal stress. It has been used as a coating process since the early 2000s, but more recently, several companies have adopted cold spray for additive manufacturing because it can print at 50 to 100 times faster than typical metal 3D processes. And no inert gas or vacuum chamber is required.

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.

Melted direct energy deposition

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

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

7. Sheet lamination

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Sheet lamination is technically a form of 3D printing and is very different from the techniques mentioned above. Its function is to stack and laminate very thin sheets of material together to create a 3D object or stack, which is then mechanically or laser cut to form the final shape. Layers of material can be fused together using a variety of methods, including heat and sound, depending on the material, which ranges 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 for battery technology and to produce composite materials because the materials used can be interchanged during the printing process.

• Types of 3D printing technologies: Laminated Object Manufacturing (LOM), Ultrasonic Consolidation (UC)
• Material: paper, polymer and sheet metal
• Dimensional accuracy: ±0.1 mm
• Common applications: non-functional prototypes, multi-color printing, casting molds.
• Advantages: rapid production and composite printing
• Disadvantages: low precision, a lot of waste, some parts require post-production

Laminated Additive Manufacturing

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

Visco Lithography Manufacturing (VLM): VLM is BCN3D’s patented 3D printing process that laminates thin layers of highly viscous photosensitive resin onto a clear transfer film. A 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 is not yet commercialized, but could also be one of the lamination 3D printing technologies.

Composite-based additive manufacturing (CBAM): Startup Impossible Objects has patented this technology, which fuses carbon, glass or Kevlar pads with thermoplastics to create parts.

Selective Laminated Composites Manufacturing (SLCOM): EnvisionTEC, now known as ETEC and owned by Desktop Metal, developed this technology in 2016 that 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, which do not cover all 3D printing technologies on the market.

China 3D Printing Manufacturer: Advance and Features

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