Overview of various 3D printing technologies
This chapter is intended for those who are interested in different printing technologies and want to learn about the differences between them. The chapter will review the currently available printing technologies and explanations each method in particular.
Preface
Since there is a wide selection of printing technologies, a number of different technologies can address a particular need. Information on the various uses of 3D printing can be found in the Chapter Two guide This. Each printer is endowed with its own features, from which arise its advantages and disadvantages in carrying out each project. The printers differ from each other in their resolution, printing speed, printing cost, properties of the materials with which they can work, and more. So how do you choose the most suitable printer? To this end, in the following document we have classified the printers according to the differences between each printing technology.
Material extrusion
Extrusion is a process in which a material in a certain shape and structure is forced, by compression passing through a body with a smaller cross-sectional area in this way a new cross-sectional area is obtained and the shape of the material changes. This process is similar to using a hot glue stick in which the glue stick is compressed through a small pinhole and changes its shape. In this printing technology the material is threaded through a nozzle and builds the three-dimensional model layer by layer.
Fused Deposition Modeling (FDM Fused Deposition Modeling)
Also called FFF (Abbreviation for Fused Filament Fabrication.)
Printing process:
FDM printers use Thermoplastic material (a material that, when heated, softens and can be shaped without significant change in its other properties). This material comes in a coil configuration, which is compressed through a heated and molten print head in the process. The print head moves and disperses the melted material from the coil in the designed areas, thus building the model layer by layer. When the material cools it hardens.
Coil printing is the most common printing technology in the world today, as it is a relatively fast and inexpensive technology for the production of plastic models and even the production of final products. However, it does not produce a smooth finish, The connection with the supporters.
| Technology | Major manufacturers | Materials |
| FDM | Stratasys, Ultimaker, MakerBot, Markforged | ABS, PLA, Nylon, PC, fiber-reinforced Nylon, ULTEM, exotic filaments (wood-filled, metal-filled etc) |
photopolymer
Solidification of a liquid solution containing polymers following exposure to light of a certain wavelength. These are polymers that belong to the photopolymer group, polymers that bond to each other when exposed along a specific wavelength. There are several printing technologies that use this method.
SLA
stereolithography stereolithography, stereo = space, lithography = writing, printing
Printing process: The first step in this process: The stage on which the product is printed is drowned into a transparent container containing a photopolymer solution so that only a thin layer of solution is formed on the stage. The machine’s laser beam then scans the stage and solidifies the polymer on top in areas designed by the designer. Thus, it creates the first layer in the print. Then, the stage rises slightly and allows another layer of solution to form beneath the hardened polymer. Further scanning of the laser makes it difficult for the next layer and so on until the final product is obtained. Production with the help of SLA requires necessary processing after printing. In order to improve the mechanical properties of the product it undergoes a hardening process with the help of UV radiation.
DLP
Digital light processin – Digital light processing
Printing process:
This technology also uses the response of photopolymers to light exposure at a certain wavelength. Unlike the SLA technology where the laser passes through each layer individually at each point, this method uses a projector that projects at each layer at once the wavelengths that harden all the required areas immediately. Therefore, the printing time in this technology is faster than in SLA technology. The projector is a digital screen, and like our computer screens, it is made up of pixels. Therefore, the resulting layer is made of small triangles, Voxels, the three-dimensional equivalent of a pixel. As with SLA technology, this technology also requires post-printing processing – hardening with UV radiation.
SLA and DLP technologies allow the creation of parts with delicate details and they produce a smooth final finish. These features are good for making jewelry, medical devices, molds and more. Nevertheless, these technologies use thermostatic materials. Therefore, the products are fragile compared to other technologies that use thermoplastic materials.
For more information on Material Types – Read the fourth chapter of this guide .
Source: 3Dhubs
| Technology | Major manufacturers | Materials |
| SLA | Formlabs, 3D Systems, DWS | Standard, tough, flexible, transparent, & castable resins |
| DLP | B9 Creator, MoonRay | Standard & castable resins |
Powdered melt fusion
Powder Bed Fusion Abbreviation (PBF) This technology is based on the melting of a powder substrate of plastic, metal, etc., using a thermal energy source (for example a laser or an electronic beam). In each layer the whole stage is covered with a uniform and thin layer of powder. It then undergoes a melting process by the thermal source in the places defined by the model designer. Each time the stage goes down a bit and is covered with another thin layer of melted powder. Thus, at the end of printing, the solid model lies within the unmelted powder of the material. Polymer-based PBFs allow for design freedom and the production of elements with complex geometry, since this technology does not require supports. Objects printed by this method are usually suitable for use as a final product, they have mechanical strength and durability that is sometimes even better than using the same materials in traditional manufacturing technologies. Elements printed by this method can be given a completely smooth finish. Most of the limitations of this technology are due to the contraction of models in the printing process and the formation of distortions.
SLS
Selective Laser Sintering This technology uses plastic powder spread in thin layers similar to PBF. In each layer, with the help of a laser beam, the powder undergoes a process of sintering – heating the powder to a temperature that is about 80% of the melting temperature of the material, so that the powder granules connect to each other and form a hard body. At the end of the process, the model is immersed in a powder that has not undergone the process, and it can be reused. The powder should be vacuumed and the model should be cleaned with brushes, air pressure or sand spray. This technology allows the use of a wide range of polymers, flexible materials, materials containing flame retardants, glass fibers, and more. This technology enables the production of final models that are intended for use as finished products.
SLM
Selective Laser Melting This technology is used to create metal models by completely melting the powder using a laser. There is a similar technology called DMLS, in which the powder is heated to a point close to melting, in which the material binds together chemically. The DMLS method works with alloys only, while the SLM allows work with separate metallic foundations (e.g. aluminum). The process is carried out in a cold, closed and oxygen-depleted cell by flowing inert gas (gas that does not undergo chemical processes under normal conditions and is used to prevent unwanted chemical reactions in the metal such as oxidation and hydrolysis). Unlike SLS technology, this technology requires supporters in order to compensate for the excess pressures produced in the model building process. In addition, proponents help reduce distortions in the model. The resulting products are strong and ready to use. The use of this technology is common in the field of dentistry for the creation of a base for titanium “crowns”.
EBM
Melting with the help of Electron Beam Melting Another technology used in the creation of metal models. The technology is based on electron beam melting, unlike SLM which uses a laser. This technology produces less excess pressure in parts, so the risk of distortion decreases and the need for supports decreases. This technology requires less energy and produces layers faster than SLM and DMLS, but the products come out lower quality in terms of layer thickness, grain size, and surface finish. In addition, the process requires the use of conductive materials only and must be done in an empty condition.
MJF
Sintering by injecting a substance into a Multi Jet Fusion powder substrate This technology is based on injecting a material into a plastic powder and exposing it to infrared energy that causes melting and precise formation of the printed layer. Basically, it is a combination of SLS technology and inkjet technology. This technology works by uniformly dispersing plastic powder, into which a crystallizing material is injected by the print heads in the desired areas that encourages melting of the material when exposed to an infrared energy source. This is how the boundaries of the object are defined in a clear and precise way. Then, a strong source of infrared energy passes over the construction surface and causes melting in the areas where the crystallizing material is dispersed.
Comparison between MJF and SLS Polymer-based PBFs allow for design freedom and the production of elements with complex geometry as this technology does not require supports. Objects printed by this method are usually suitable for use as a final product, they have strength and mechanical durability that is sometimes even better than using identical materials in traditional manufacturing technologies. Elements printed by this method can be given a completely smooth finish. Most of the limitations of this technology are due to the contraction of models in the printing process and the formation of distortions.
| technology | Major manufacturers | Materials |
| SLS |
EOS, 3D Systems,
For an overview of the various SLS printers available on the market
For a review of EOS SLS printers |
Nylon, alumide, carbon-fiber filled nylon, PEEK, TPU |
| SLM / DMLS | EOS, 3D Systems, Sinterit | Aluminum, titanium, stainless steel, nickel alloys, cobalt-chrome |
| EBM | Arcam | Titanium, cobalt-chrome |
| MJF |
HP
For an overview of the HP 4200 machine:
For an overview of the HP 580 machine: |
Nylon |
Material Jetting
In this technology, similar to inkjet technology, the print heads drip small drops of material. Unlike MJF, these are thousands of drops of a liquid substance that has difficulty exposing to UV or heat. In addition, this material is not some formative material, but the material itself from which the final model will be composed. This technology allows printing on several materials simultaneously and even water-soluble supports can be printed.
NPJ - nanoparticle injection
NPJ technology uses a special liquid that contains nanoparticles of various metals. The print heads drip the liquid into the designated places on the print tray. Due to the high heat in the printing process, the liquid in which the metal particles are located evaporates, leaving behind layers of metal. This technology makes it possible to produce models from metal significantly faster than laser-based printers.
This technology is suitable for the production of precise parts, with a smooth finish that can be used as a final product.
| Technology | Major manufacturers | Materials |
| Material Jetting | Stratasys (Polyjet), 3D Systems (MultiJet) | Rigid, transparent, multi-color, rubber-like, ABS-like. Multi-material and multi-color printing available |
| NPJ | Xjet | Stainless steel, ceramics |
Binder Jetting - injection of a crystallizing material
Binder Jetting technology works by scattering layers of powder and gluing them by a crystallizing material injected on them. This technology can be used to make models from ceramic materials (gypsum, glass) and metals. The printing process involves spreading a thin layer of powder on the printing platform. Above the layer moves a print head that disperses drops of crystallizing material in places defined for this by the model designer. At the end of each layer, the print platform moves downward, a new layer of material is scattered over it, and the process repeats itself. Since this technology allows the use of “crunchy” materials such as gypsum, the products require further processing of reinforcement which is usually done with the help of a quick or epoxy glue. Similar to a home inkjet printer that prints on paper, here too you can use several colored ink cartridges simultaneously and thus get colored models. This method is suitable for the creation of aesthetic models such as architectural models, but it is not intended for the production of active components as the parts are very fragile. Metal printing with this technology is cheaper than SLM and DMLS technologies, but the products have less mechanical properties.
| Technology | Major manufacturers | Materials |
| Binder Jetting | 3D Systems, Voxeljet | Silica sand, PMMA particle material, gypsum |
| ExOne | Stainless steel, ceramics, cobalt-chrome, tungsten-carbide |
Direct Energy Deposition - DED
Direct Energy Deposition
This technology is for metals only, and works by directly melting powder in the area where it is applied. In addition, it allows adding material on existing components.
This technology uses a laser or an electron beam. The laser creates a melting pool where it is intended to be a material, and a material scattered in the area. Thus the powder is melted and then solidifies as it cools. The base on which the model is built is usually a metal tray or an existing component. This technology enables the manufacture of new parts as well as the repair of existing parts or the addition of elements on existing parts.
| Technology | Major manufacturers | Materials |
| LENS (לייזר) | Optomec | Titanium, stainless steel, aluminum, copper, tool steel |
| EBAM (קרן אלקטרונים) | Sciaky Inc | Titanium, stainless steel, aluminum, copper nickel, 4340 steel |
