3D Printing

The 3D printing process builds a three-dimensional object from a computer-aided design (CAD) model, usually by successively adding material layer by layer, which is why it is also called additive manufacturing, unlike conventional machining, casting and forging processes, where material is removed from a stock item (subtractive manufacturing) or poured into a mold and shaped by means of dies, presses and hammers Days the transistors are classified into different types depending on either construction or operation, they are explained using tree diagram as below.

3D Printing Types
Fused Deposition Modeling (FDM)
Stereo lithography (SLA)
Selective Laser Sintering (SLS)
Multi-Jet-Fusion (MJF)
Direct Metal Laser Sintering (DMLS)
Polyjet

1) Fused Deposition Modeling (FDM)

The materials mostly used are thermoplastic polymers (e.g., PLA, ABS, polyurethane) and come in a preextruded filament shape. In the process, a coil of thermoplastic filament is first loaded into the machine. Once the nozzle has reached the desired temperature (e.g., close to the melting temperature of the polymer), the filament is fed to the extrusion head, then in the nozzle where it melts. The extrusion head is attached to a two-axis system that allows it to move in x-y directions. The melted material is extruded in thin strands and deposited layer-by-layer in predetermined locations, as described in the STL file. Sometimes the cooling of the material on the platform is accelerated through the use of cooling fans attached on the extrusion head. When a layer is finished, the build platform moves down in z direction, and a new layer is deposited. This process is repeated until the part is complete.

2) Stereo lithography (SLA)

Stereolithography (SLA or SL; also known as stereolithography apparatus, optical fabrication, photo-solidification, or resin printing) is a form of 3D printing technology used for creating models, prototypes, patterns, and production parts in a layer by layer fashion using photochemical processes by which light causes chemical monomers and oligomers to cross-link together to form polymers. Those polymers then make up the body of a three-dimensional solid. Research in the area had been conducted during the 1970s, but the term was coined by Chuck Hull in 1984 when he applied for a patent on the process, which was granted in 1986.Stereolithography can be used to create prototypes for products in development, medical models, and computer hardware, as well as in many other applications. While stereolithography is fast and can produce almost any design, it can be expensive
3) Selective Laser Sintering (SLS)

Selective Laser Sintering (SLS) is an industrial 3D printing process ideal for manufacturing end-use parts.
Selective laser sintering (SLS) is an additive manufacturing (AM) technique that uses a laser as the power source to sinter powdered material (typically nylon or polyamide), aiming the laser automatically at points in space defined by a 3D model, binding the material together to create a solid structure. It is similar to Selective Laser Melting (SLM); the two are instantiations of the same concept but differ in technical details. Selective laser melting (SLM) uses a comparable concept, but in SLM the material is fully melted rather than sintered, allowing different properties (crystal structure, porosity, and so on). SLS (as well as the other mentioned AM techniques) is a relatively new technology that so far has mainly been used for rapid prototyping and for low-volume production of component parts. Production roles are expanding as the commercialization of AM technology improves.
4) Multi-Jet-Fusion (MJF)

Multi Jet Fusion is a powder-based technology but does not use lasers. The powder bed is heated uniformly at the outset. A fusing agent is jetted where particles need to be selectively molten, and a detailing agent is jetted around the contours to improve part resolution.
MJF produces parts from engineering thermoplastics. Here is the list of our standard MJF 3D printing materials. In MJF, parts are built by jetting a binding agent onto thin layers of polymer powder particles (typically nylon) and then sintering them using an IR heat source.

5) Direct Metal Laser Sintering (DMLS)

Direct metal laser sintering (DMLS) is one of the few 3D printing technologies that directly create a metal part from its 3D computer model. This process is an advancement of powder metallurgy (PM), a mature metal-molding technology that uses heat and pressure to form powdered metal parts. The working material for this 3D printing process is finely powdered metal. Typically the manufactured size of the metal particles is 20 – 40 micrometers. The particle size and shape limit the detail resolution of the final part. Smaller metal particle size and less variation allow better resolution.
Other resolution limits in this technology are the layer height and the size of the laser spot. Like other 3D printing processes, the model is divided into many fine layers, which are then printed one-by-one to build the final part. Printable layer heights are approximately the maximum size of the metal powder used.

6) Polyjet

Unlike other 3D printing technologies, there isn’t a single inventor for MJ. In fact, up until recent times it’s been more of a technique than an actual printing process. It’s something jewelers have used for centuries. Wax casting has been a traditional process where the user produces high-quality, customizable jewelry. The reason it gets a mention here is because of the introduction of 3D printing. Thanks to the arrival of this technology, wax casting is now an automated process. Today, MJ 3D printers produce high-resolution parts, mainly for the dental and Jewelry industries,
Once the 3D model (CAD file) is uploaded to the printer, it’s all systems go. The printer adds molten (heated) wax to the aluminum build platform in controlled layers. It achieves this using nozzles that sweep evenly across the build area. As soon as the heated material lands on the build plate it begins to cool down and solidify (UV light helps to cure the layers). As the 3D part builds up, a gel-like material helps to support the printing process of more complex geometries. Like all support materials in 3D printing, it’s easy to remove it afterward, either by hand or by using powerful water jets. Once the part is complete you can use it right away, no further post-curing necessary.
There are also Polyjet MJ 3D printers, which use photopolymer-resins rather than synthetic waxes. Polyjet technology also offers very good resolution. Unlike digital wax printers, people use Polyjet devices to create parts for a wide range of industries.

Reference
https://3dinsider.com/3d-printer-types/
https://www.researchgate.net/figure/PolyJet-3D-printer-machine_fig2_253238720
https://en.wikipedia.org/wiki/3D_printing
https://www.3dhubs.com/3d-printing/processes/material-jetting/#polyjet-materials

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