Summary of basic 3D printing technologies

The world of 3D printing is more diverse than it might seem. It has found its significant use in industrial fields such as construction or the automotive industry. But you can also come across it in healthcare, paleontology or the food industry. For example, you can taste chocolate made with a 3D printer. But there is no 3D printing like 3D printing. Probably the most well-known method that comes to mind when most people think of 3D printing is printing with the help of a heated filament that flows through a nozzle and creates the desired shape on the printing pad by layering. But it would be a shame to stick with just this method. Because the term 3D printing covers several methods that are quite different from each other and also use different machines and materials for production.

7 basic types

Method name

Material extrusion

Technology name: Fused Filament Fabrication (FFF), Fused Deposition Modeling (FDM)

Vat polymerization

Technology name: Stereolitography (SLA), Direct Light Processing (DLP)

Powder bed fusion

Technology name: Slective Laser Sintering (SLS), Direct Metal Laser Sintering (DMLS), Selective Laser Melting (SLM), Electron Beam Melting (EBM)

Material jetting

Technology name: Material Jetting (MJ), Drop On Demand (DOD)

Binder jetting

Technology name: Binder Jetting (BJ)

Direct energy deposition

Technology name: Laser Engineering Net Shaping (LENS), Laser-Based Metal Deposition (LBMD)

Sheet lamination

Technology name: Ultrasonic Additive Manufacturing (UAM), Laminated Object Manufacturing (LOM)

It is one of the most well-known and widespread methods. And as the name suggests, printing takes place using the extrusion of material - filament (you may also come across the term printing string or fiber) through a heated nozzle. Filament (popular materials include ABS or PLA) is melted into a layer of compound during printing and applied via a heated nozzle to the print bed. This process is dictated by software. After the filament has cooled down, you can enjoy the print you just printed. The procedure sounds quite simple, and perhaps that is why this method has built up a number of basic fans.

The second reason is that very diverse materials can be used for the fiber. Among the typical thermoplastic (the most popular ABS - acrylonitrile butadiene styrene) and PLA - polylactic acid are worth mentioning), but in addition to the basic types, there are also various additives (e.g. wooden or metal).

Material Extrusion subcategory:

• FDM - Fused Deposition Modeling

• Structural 3D printing

• Micro 3D printing

• Bio 3D printing

Which materials can be used:

Dimensional accuracy:

±0,5 % (lower limit ±0,5 mm)

prototypes and models, design and decorative prints, cases and packaging, houses, etc.

• the possibility of using various materials
• affordable (compared to other methods, it is among the cheapest)

• not the most accurate compared to other methods
• the properties of the material are sometimes less durable (hardness, durability)

Bio 3D printing falls under the extrusion method (although there are other bio printing methods) and works similarly to the FDM method, only in this case it uses organic or biological materials such as living cells and nutrients to print. It has found its application in the medical field, specifically in research, press bodies, tissue engineering (bone regeneration) or perhaps in cell therapy. It is also used for drug testing and development or the production of medical equipment. Instead of conventional thermoplastic, the industry uses so-called bio ink, which consists mainly of living matter, and uses collagen, gelatin, hyaluronan, silk, alginate or nanocellulose as a carrier material. This is an interesting method that, if expanded, has great potential in the medical world.

Structural 3D printing again falls into the method where the material is extruded through a nozzle. Even the procedure is relatively the same as with classic FDM technology, only the difference is in the material used and the design of the printer. Specially prepared concrete (or mortar) is used as material, which is extruded through a nozzle. In this case, the 3D printer has huge dimensions (we are talking about several tens of meters in height) and is usually assembled from several robotic arms, or the print head can run on rails. Currently, this type of 3D printing is in its infancy and research is underway. But it is certain that if the possible potential can be exploited, it could fundamentally reduce the cost of building houses, since not so much labor would be needed. The interesting thing is that there are researches that remain the possibility of printing buildings on Mars using the soil obtained there, which would be used in the future by expeditions sent to search and discover the red planet Mars.

Polymerization, or 3D printing using resin, is the second main group of 3D printing methods. During the printing process, it uses a light source to selectively cure the photopolymer resin in a special printing tray, where the light is precisely directed to a certain point of the resin so that it can be cured. When the first layer has cured, the printer will move up or down (depending on the type of printer) - usually between 0.01 and 0.05mm to allow the next layer to cure.

This process is repeated until the final print is completed. The material used in this method is called resin. We can divide it into different categories - for example: castable, standard, strength, dental, industrial, biocompatible or flexible. These resins differ in properties according to their use. After the print is finished, the print is cleaned of excess resin and allowed to finally harden (a special UV chamber can be used for this).

Vat polymerization subcategory:

• SLA - Stereolithography
• DLP - digital light projector
• LCD - liqud crystal display or MSLA - Masked Stereolithography

Dimensional accuracy:

• high accuracy possibility to achieve
• high resolution details
• very smooth surface
• almost invisible individual layers on the print

• smaller print area
• toxicity of liquid resins

Differences in the types of polymerization methods:

SLA – A UV laser shines into a tub of resin and traces the object to be created on its surface

DLP – a digital projector shines into a tub of resin, which then solidifies

LCD / MSLA – the projector shines on the LCD display, which is located above the tub and transmits light only where the polymer is to be cured

This technology uses a semiconductor laser for printing, which is directed through a special mirror into a tub with mirror resin, where selective curing takes place. The beam moves up almost imperceptibly, creating layer after layer. This process ensures that the individual layers are printed so that they are difficult to see. This makes the print extremely smooth. Another advantage is that the models have perfect details. On the other hand, time could be included among the disadvantages, because in the DLP method, where the model is confirmed uniformly, this method is somewhat more time-consuming. When printing, you also need to be careful when handling the resin, as it is a toxic material. So it is necessary to prevent it from coming into contact with the skin and you don't get vapors. For some users, the printing surface, which is not very large, could be a limitation. After printing, you need to wash the model in isopropyl alcohol and let the resin harden (the surface is sticky to the touch). You can do this in the sun, but it will use a UV lamp faster.

Microstereolithography (µSLA), which focuses on printing miniature models at a resolution between 2 microns (µm) and 50 microns. As with other types of 3D printing that fall into the SLA group, it uses a laser for curing. But in order for prints to be created in such small dimensions, a specialized resin, a highly sophisticated laser and lenses are used, which have the task of generating small points of light.

The TPP method uses a femtosecond laser to print and can print models that can be even slightly smaller than the µSLA method. Using this laser, individual 3D pixels, also known as voxels, which are in nano- to micrometer sizes, are also hardened. The resulting print is so large that it is only a few millimeters. But even in these tiny dimensions, it can maintain the resolution of details in the order of nanometers. If you are now wondering where these small prints can be used, they are medical applications or perhaps optical sensors and microelectrodes.

The light can be projected using screens that emit LED light (micrometer size) or by UV light that is directed using a digital micromirror device (DMD). This device allows different points of light in different places on a single layer. There is a selection of different DLP printers on the market, which can differ in the components used and the quality of the light source. A wider price range also depends on this.

This technology is an additive manufacturing technology in which thermal energy selectively sinters thin layers of powder, creating a solid object layer by layer. The printer applies a thin layer of powder material to the printing pad, then uses light energy (usually from a laser) to connect specific points on the powder layer, then another layer of powder is applied, which fuses to the previous one. This is done until the entire model is printed. The process may vary depending on the material used (if it is metal or plastic). The resulting prints tend to have high mechanical properties, they can be functional and it is not a problem to print even more complex geometric shapes.

Powder Bed Fusion subcategory:

• Selective Laser Sintering (SLS)
• Laser Powder Fusion (LPBF)
• Electron Beam Melting (EBM)

Dimensional accuracy:

• high strength and resistance
• widespread use in the industrial area

The SLS method uses plastic powder as a material, which is sintered with the help of a laser. The procedure is as follows - a container of polymer powder is heated to a temperature just below the melting point of the polymer, then a very thin layer of powder (usually 0.1 mm thick) is applied to the printing pad. The laser then begins to scan the surface according to the pattern set in the digital model and sinter the powder, which solidifies the print. When the entire cross-section is scanned, the build platform moves one layer thickness vertically and applies another layer of powder and sinters again. This process is repeated until the entire object is completed. The unbaked powder remains in the printer, which provides stability to the object, which can reduce the need for supports or avoid them altogether. After both printing and cleaning are complete, no further post-processing is necessary, but you can polish or color-adjust the prints if desired.

The EBM method, sometimes called electron beam powder fusion (EB PBF), focuses on metal printing similar to LPBF, but uses an electron beam instead of a laser. This technology is used to make parts such as titanium orthopedic implants, turbine blades for jet engines and copper coils. EBM uses an electron beam instead of a laser for several reasons. One of them is that el. the beam will generate more energy and heat, which is required for certain metals and applications. Another reason is that no gas chamber is used, but EBM printing is in a vacuum chamber to prevent beam scattering. The temperature of the chamber can reach up to 1,000 °C (in some cases even higher).

The electromagnetic beam moves at a higher speed than the laser and can even be split into several areas at the same time. One of the advantages of EBM over LPBF is its ability to process conductive materials and reflective metals such as copper. Another feature of EBM is the ability to stack individual parts on top of each other in the chamber so they are not necessarily attached to the board, greatly increasing the volume option. Electron beams generally produce thicker layers and less surface detail than lasers.

Material jetting subcategory:

• Materiál Jetting (MJ)
• Nanoparticles Jetting (NPJ)

Dimensional accuracy:

• textured finish
• possibility to combine several colors and materials

Disadvantages:

• not suitable for demanding mechanical parts
• higher price than other technology that uses resin

Material jetting is a method where a layer of photosensitive resin is selectively applied to a printing substrate and cured by ultraviolet (UV) light. After one layer is applied and cured, the build platform is reduced by one layer thickness and the process is repeated to create the 3D object. The M-Jet method can create excellent details faster than filament 3D printing (FDM). It is often used for prototypes in different colors and textures. The blasting of materials may not always be the same for different manufacturers. The names of this method also differ. You can meet PolyJet from Stratasys or MultiJet Printing (MJP) from 3D Systems. In this method, the printer prints from the print heads in rows, allowing multiple objects to be printed in one row without affecting speed. If the space on the print bed is properly adjusted in each production line, the M-Jet printer can produce parts many times faster than other 3D printers that use resin to print.

It is one of the few technologies that defies easy classification. The nanoparticle jetting method developed by XJet uses an array of print heads with thousands of ink jets that simultaneously spray millions of ultra-fine droplets of material in ultra-thin layers.

Metal or ceramic particles are compressed in the liquid. The process takes place under high heat, which vaporizes the liquid during blasting, leaving usually only metal or ceramic material.

The resulting 3D part has only a small amount of residual binder, which is removed in the subsequent sintering process.

Whether it is metal, plastic, sand or other powder material, the process of blasting the binder is the same. First, a thin layer of powder is applied to the building platform. Then a print head with ink jets passes over the printing pad and selectively applies droplets of binder to bond the powder particles together. Once a layer is complete, the build platform is moved down and the process is then repeated until the entire section is complete. The binder acts as a glue to hold the polymer powder together. After printing, the parts are coated with unused powder and left to cure.

After that, the parts are removed from the powder container, the excess powder is collected and can be used again. After that, depending on the material, additional processing is sometimes required (does not apply to sand in most cases). The surface can be polished, painted and sanded.

Binder Jetting subcategory:

• metal bond blasting
• polymer binder blasting
• sandblasting of binder

Dimensional accuracy:

• low price
• possibility to print voluminous
• prints printing functional metal parts
• excellent color
• reproduction high print speed
• design flexibility without support

Disadvantages:

• it is a multi-step process for metals
• polymer parts are not durable

Overall, the material properties of parts produced by this method are the same as those of metal parts produced by metal injection molding (which is one of the most widely used production methods for mass production of metal parts). In addition, parts of the jet binder show a more smooth surface.

Metal parts created by binder jetting require secondary processes after printing is completed to achieve good mechanical properties. Directly printed parts essentially consist of metal particles bonded together with a polymer adhesive. These so-called "green parts" are fragile and cannot be used as is.

Plastic bond shot blasting is a very similar process to metal bond shot blasting in that it involves powder and liquid binder, but the applications for which it is used are very different. Once printed, the plastic parts are removed from the powder bed, cleaned and often can be used without further processing, but these parts lack the strength and durability that 3D printed parts otherwise possess (such as SLS, where the polymer powder is essentially melted ). Parts created by blasting plastic binder can be filled with other material to increase strength. This method is valued for producing multi-colored parts that will function as prototypes or that are used in a medical environment.

The low cost and speed of the process make this method an excellent solution for foundries. Elaborate pattern designs that would be very difficult or impossible to produce using traditional techniques can be printed in a matter of hours.

The future of industrial development continues to place high demands on foundries and suppliers. Sandblasting of binder offers its great potential. After printing, the prints are removed and cleaned to remove any loose sand. Molds are usually immediately ready for casting. After casting, the mold is broken and the final metal part is removed.

During the Multi Jet Fusion process, the printer applies a layer of powder material (usually nylon) to the print bed. Then the ink head moves over the powder and applies a fixing and detailing reagent to it. After printing, the infrared heating unit then moves. Wherever fixative has been added, the undercoat will melt together, while the detailing reagent areas will remain in powder form. The powder parts are peeled off, which creates the desired shape. This also reduces the need for modeling supports as the lower layers support those printed above them. To complete the printing process, the entire powder bed—and the parts printed within it—is moved to a separate section. Here, most of the loose, unmelted powder is vacuumed up, allowing it to be reused instead of producing excess waste. Multi Jet Fusion is a versatile technology that has found use in several industries from automotive to healthcare to consumer product manufacturing.

This technology is used to create a print layer by layer, but is often used to repair or modify metal objects by applying the material directly to an existing metal part. After the printing is finished, CNC machining usually follows to achieve greater durability. The combination of DED and CNC manufacturing types is so common that there is a subtype of 3D printing called hybrid 3D printing that uses hybrid 3D printers that consist of a DED and a CNC machine. The technology is valued as a faster and cheaper alternative to casting and forging metal parts in smaller quantities and for repairs for applications in the offshore oil and gas industry or perhaps in the aerospace and energy industries.

Directed energy deposition subcategory:

• powder laser energy deposition
• wire additive manufacturing (WAAM)
• wire electron beam deposition
• cold spray

a wide variety of different metals that can be in wire and powder form

Dimensional accuracy:

• high production speed
• option to apply to existing components

Disadvantages:

• unable to create complex shapes due to inability to create support structures
• generally poor finish and lower accuracy

This method is also sometimes called laser metal deposition (LMD) or laser modified mesh forming (LENS). It is a 3D printing technology that uses metal powder or wire fed by one or more nozzles and melted using a powerful laser onto a construction platform or directly onto a metal component. The object, which is placed on a multi-axis rotary table, is created layer by layer. The manufacturing process is faster than powder bed fusion, but results in lower surface quality and significantly lower accuracy, often requiring extensive post-machining. DED laser printers often have sealed chambers filled with argon to prevent oxidation. They can also only work with localized argon or nitrogen when processing less reactive metals. Metals commonly used in this process tend to be stainless steel, titanium and nickel alloys. This printing method is often used to repair high-end aerospace and automotive components such as jet engine blades, but it is also used to produce entire parts.

Cold spray is a DED 3D printing technology that sprays metal powders at supersonic speeds to bond them together without melting them, producing almost no thermal stress that can cause heat cracking or other common problems that can affect based technologies on the principle of melting. Since the early 2000s, this method has been used to deposit a layer on parts, but recently several companies have adapted cold spraying for additive manufacturing because it can layer metal in precise geometries down to a few centimeters at about 50 to 100 times the speed of typical metal 3D printers, and no inert gases or vacuum chambers are needed. Like all DED processes, cold spraying does not produce prints with excellent surface quality or detail, so it will be ideal for use where appearance is not as important. Prints do not need to be edited afterwards.