3D Printing Technology

Fused Deposition Modeling (FDM)

FDM is the most commonly used 3D printing technology, it is the one that comes to our mind as soon as someone mentions 3D printing. In this method, the material, usually, a thermoplastic, is extruded layer by layer through a nozzle which builds the required object. The material is fed into the nozzle as thin threads called filaments. The nozzle then melts the material and deposits it on the base, also called the build platform. As soon as a layer is completed, the base moves down a bit and the process continues till we obtain the final object. FDM is one of the most economical and the simplest way to achieve 3D printing, albeit slower than many of its counterparts like SLS and SLA.

FDM - 3D Printing Technology

Stereolithography (SLA)

This is a 3D printing process that uses UV laser to cure liquid resin into hardened plastic, Upside down/Inverted SLA is the most common type of SLA. Depending on the machine resin is either poured into the tank by a user or dispensed automatically from a cartridge. At the beginning of the print, a build platform is lowered into the resin leaving a thin layer of liquid in between the platform and the bottom of the tank. Galvanometers direct the UV laser through a transparent window at the bottom of the resin tank, drawing a cross-section of the 3D model and selectively hardening the material. The print is built-in consecutive layers, each less than a hundred micron thick. When a layer is completed, the part is peeled from the bottom of the tank, letting fresh resin flow beneath, and the platform is lowered once again.

SLA - 3D Printing Technology

Selective Laser Sintering (SLS)

Selective Laser Sintering or SLS 3D printing is relied on for printing strong, functional nylon parts. In this process, the powder is dispensed in a thin layer on top of a platform inside the build chamber. A laser beam heats the powder to just at the melting point of the material according to a cross-section of the object to be made. This fuses the particles to create a solid body, then the platform is lowered by one layer in the build chamber and the process is continued till all the cross-sections get printed. In this process, the unfused powder acts as the support and hence the need for dedicated support structures is eliminated, thereby enabling complex parts to be printed out.

SLS - 3D Printing Technology

Digital Light Processing (DLP)

Similar to SLA printers, photosensitive resins are used in this process of 3D printing. A build platform descends in the resin tank to build the object layer by layer. The differentiating factor from SLA is the light source, DLP 3D printers use a digital projector screen to flash an image of a layer across the entire platform, curing all points simultaneously. Due to a projector being used which is a digital screen, the image of each layer is constructed of square pixels, resulting in a three-dimensional layer formed from small rectangular cubes called voxels, which is different from SLA where the layers are constructed using rounded lines created by the laser beam.

DLP - 3D Printing Technology

Multi Jet Fusion (MJF)

This is a relatively new 3D printing process, invented by HP in 2016. In this process, a layer of material powder is put on the printing bed. After that, an inkjet head deposits a fusing and a detailing agent across the bed. An energy source is then passed over the bed. Wherever the fusing agent was added, a reaction takes place and the underlying layers get fused whereas the areas where the detailing agent was added remain unaffected and fall off. In this process, the lower layers of powder act like a support to the upper layers, hence the need for exclusively printing supports is eliminated. After the printing is done, the entire powder bed is moved to a separate processing station where the powder is vacuumed off leaving the printed part. This process is quite similar to SLS but in MJF a new material layer is placed when the previous layer is still molten, this facilitates complete fusion of both layers to take place providing improved print durability and finer detail compared to other printing methods.

MJF - 3D Printing Technology

Direct Metal Laser Sintering (DMLS)

This is one of the methods by which metals can be 3D printed. This process is similar to SLS with the powder being of metallic nature. Typically the manufactured size of the metal particles is 20 – 40 micrometres, this size of the particle determines the resolution of the final printed object. The smaller the metal particles, the better will be the resolution. The size of the metal particle also determines the printable layer height, limited by the maximum size of the metal particles in use.

DMLS

Electron Beam Melting (EBM)

This is another method by which metal 3D printing of the metal can be performed. Electron Beam Melting (EBM) is part of the powder bed fusion family which uses an electron beam to fuse metal particles. An energy source that can emit the electron beam is used in a vacuum environment to avoid the collision of the electron beam with the gas particles in the atmosphere. As the process is based on the principle of electric charges, a conductive material is needed or else there will be no interaction between the powder material and the electron beam. This eliminates materials like ceramics to be printed using this process. A layer of powder is put on the build platform which is targeted by an electron beam. The electron beam is controlled by a set of electromagnetic coils, which accurately point the beam towards the desired points of the build platform. The material over where the beam travels gets melted and fused. Compared to a process using laser, electron beams can be split to heat the material in several places continuously, speeding up the build time considerably. This does come at a cost of reduced precision as at the powder level, an electron beam is wider than a laser beam.

EBM

Conclusion 

3D printing has revolutionized the process of rapid prototyping and the methods of production of different parts considered to be too complex to be made by machines. Different types of 3D printing technology can be utilized depending on different situations. Nowadays 3D printing technology has become cheap enough to be adapted for personal use and people can create new objects with much more ease compared to just a few years ago. The improvement in this field is an exciting avenue to look after. 

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