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Additive manufacturing is a method of manufacturing that adds material in certain patterns to create the desired shape instead of removing material to create a part. It is said that 3D Printing or additive manufacturing is a process of making three dimensional solid objects by adding material layer by layer (European Social Fund, 2013). The most areas that use the 3D printing is for prototyping specific parts for example aerospace, military, biomedical engineering, dental, for hobbies and home use and for future applications such as medical (body parts), buildings and cars.
3D printing is a method that use the specifics software that slices the 3D model into layers of 0.01mm thick or less in most cases. Then, each layer is traced onto the build plate by the printer, once the each pattern is completed, the build plate is lowered for the next layer is added on top of the previous one. 3D Printing reduced some waste since the material is placed in the location that need to be use only, the rest will be left out as empty space.
In addition, by using 3D Printing it is possible to produce specific objects that almost any shape and form (European Social Fund, 2013).
By using 3D printing, there is a variety of printing processes or method of printing to create physical objects from digital designs. The main differences between these processes are in the procedure of layers are deposited to create parts and in the materials that are used. Some of the methods melt or soften material to produce the layers, while others cure liquid materials using different advanced technologies.
Each method has its own advantages and drawbacks.
A 3D printer includes a machine that have a set of components that runs simultaneously to produce the desired output from the input digital file. Figure 2.1 shows the main component of 3D printer for FDM type:
Figure 2.1: Main component of 3D Printing of FDM (apm.design, 2019)
2.2.1 Print Bed (Tray)
This is the flat platform where the 3D models are layered during the printing process. The print bed may be ambient or heated depending on the types of filament used in the printer. The heated print beds are used to keep the printed area of the print warm during the layering process to prevent warping (Alex Beaudoin et al., 2016).
The extruder is the part that thrusts out and feeds the plastic filament into the 'hot-end'. Figure 2.2 shows the part of the extruder on 3D printer. Extruders are typically place together with the hot-end, however in some types of 3D printer it can be remote, pushing the filament through a tube that called a Bowden cable into the hot-end. In some types a dual extruder is used, which print with two different materials at the same time. This added feature will increased the price, as it requires an extra extruder and hot end.
Figure 2.2: 3D printer extruder (Alex Beaudoin et al., 2016)
Figure 2.3 shows the hot-end is composed with a heat source, a temperature sensor and an extrusion tip where the plastic filament is feed through to deposit molten material. The hole in the slot may be in a range size, typically between 0.2mm and 0.8mm. The smaller the nozzle, the more detailed the print, but the longer it takes for the thinner layers to stack up (Alex Beaudoin et al., 2016).
Figure 2.3: 3D printer hotend (Alex Beaudoin et al., 2016)
The filament is the input material which is expressed as a 3D solid object by the printer. Like an inkjet inject ink, a 3D printer emits the melted filament. Figure 2.4 shows the example of ABS material filament for 3D printer.
Figure 2.4: Example of ABS Filament (LulzBot 2014)
There is a variety of 3D printer that to create physical part from digital designs. The differences between the 3D printers are in the method of the layers are deposited to create parts and the materials that are used. Some techniques melt or soften material to produce the layers, while others cure liquid materials using different advance technologies. Each type of 3D printer has its own specialty. Here are some common technologies:
2.3.1 Stereo lithography (SLA)
Figure 2.5 shows the SLA component that placed the platform below the surface of a vat of liquid polymer. A UV (Ultra Violate) laser beam then marks the first slice of an object on the surface of this liquid, causing to harden a thin layer of photopolymer. The punctured platform is then lowered very slightly for another slice is traced out and hardened by the laser. This procedure is repeated until a complete object has been printed and be removed from the vat of photopolymer, drained of excess liquid, and cured.
Figure 2.5: Process of Stereo lithography (SLA) (CustomPartNet, 2008)
2.3.2 Fused deposition modelling (FDM)
FDM is a hot thermoplastic is extruded from a temperature-controlled print head to produce fairly tough objects to a high degree of accuracy. This machine works with the moving of the extruder that feeds with the filament layer by layer onto the platform until the part produced (European Social Fund, 2013). Figure 2.6 shows the main component and the process of FDM.
Figure 2.6: Fused Deposition Modeling process. (CustomPartNet, 2008)
2.3.3 Selective laser sintering (SLS)
Figure 2.7 shows the process and the main component of SLS. This builds the parts that uses a laser as the power source to sinter powdered material such as nylon or polyamide. Then, targeting the laser automatically at points in space defined by a 3D model, binding the material together to produce a hard structure (European Social Fund, 2013).
Figure 2.7: Main component of Selective laser sintering (SLS) (CustomPartNet, 2008)
2.3.4 Multi-jet modelling (MJM)
Figure 2.8 shows the main component and process of MJM. This machine forms up objects from successive layers of powder, with an inkjet-like print head used to spray on a binder solution that sticks only the required granules together.
Figure 2.8: Main component of Multi-jet modelling (MJM) (CustomPartNet, 2008)
Throughout the years, 3D printing industry has been growing and new improvements are being introduced. New 3D printing machines are being developed to print different kinds of materials such as plastics, metals, composites and many more. When it comes to industrial 3D printing, there is a wide range of materials to choose from for every product. Every materials have their own unique features, strengths and weaknesses. These are several materials that used for 3D printing:
Nylon that also named as polyamide is a synthetic thermoplastic linear polyamide and is the most common plastic material. Because of its flexibility, durability, low friction and corrosion resistance, it is one of the well-known 3D printing filament (SPC Surface Treatment Expert, 2017). In addition, nylon also a popular material that used in production of clothes and accessories. Nylon is suitable to use for producing complex geometries. This material is low-cost and known as one of the toughest plastic material.
2.4.2 Acrylonitrile Butadiene Styrene (ABS)
ABS is a popular choice for home-based 3D printers for its strength and safety. For example, the material of "LEGO plastic," made up of of pasta-like filaments that give ABS its solidity and flexibility. ABS is available in various colors that make the material suitable for specific products such as stickers and toys. Lastly, ABC is also used to make jewelry and vases.
This material is one of the less-used materials in 3D printing. Compared to other 3D-applicable materials, resin has limited its flexibility and strength. This material was made of liquid polymer, resin reaches its end state with exposure to UV light. Generally resin is color in black, white and transparent, but in certain printed items have also been produced in orange, red, blue and green (SPC Surface Treatment Expert, 2017).
2.4.4 Polylactic acid (PLA)
Polylactic acid is one of the eco-friendliest material for 3D printers that based from natural products such as sugar cane and corn starch so that it is biodegradable. This material is available in soft and hard forms of plastics that made from polylactic acid (SPC Surface Treatment Expert, 2017). Hard PLA is one of the strongest material and therefore more usefull material for a wider range of products.
2.4.5 Stainless steel
Stainless steel is printed by using fusion or laser sintering. There are two possible technologies that can be used for this material which are Direct Metal Laser Sintering (DMLS) or Selective Laser Melting (SLM) technologies. Stainless steel is perfect to use for miniatures, bolts and key chains since of its strength and detail (SPC Surface Treatment Expert, 2017).
Nowadays, rapid prototyping has a very wide reach. It can be used in the most different industries, institutions of education from the fundamental level up to the higher level and for private use (individuals).
By using FDM technology, one of the advantages is its geometric flexibility in the design. Studied on the design of an intake manifold for a formula SAE car also known as the Society of Automotive Engineers using FDM technology and a composite material shows that the freedom in the design helped the researchers to create a unique geometry that featured a tapered plenum and tapered runners. The results suggested that the new design provided more torque and reduced total pressure drop (Hootan Mehraein, 2018).
The ability of a researcher to choose the right 3D-printing technology is very important in aerodynamic testing. Olasesl and Wiklak manufactured four models of a standard NACA0018 aerofoil for aerodynamic testing in different methods (Multi Jet Modeling (MJM), SLS and FDM). The results showed that the surface roughness in MJM method is the lowest, while in FDM surface roughness is higher. (Hootan Mehraein, 2018).
2.5.1 3D Printing for Biomedical Applications
3D printing in the biomedical industry has an extensive range of applications in user goods and medical prosthesis. The applications used in biomedical include the production of dental crown bridges aids, customized hearing, surgical instruments, artificial joints and artificial hips, and tissue and cell printing (Hootan Mehraein, 2018).
2.5.2 Dental Industry
One of the areas that have benefitted from 3D printing in dental industry is bracket production and positioning. By using a stereo lithography (STL) 3D printer, bracket production and positioning are fused together as one unit (Hootan Mehraein, 2018). Creation of 3D physical models of a patient's skull and other structures gives an oral surgeon a realistic impression of structures before surgery. This method helps in minimizing the extra-oral time and injury while translating teeth (Hootan Mehraein, 2018).
Another application in which 3D printing technology has useful is the training of students in studies especially in the medical field. Khan and his coworker successfully 3D-printed an unruptured paraclinoid aneurysm of a 40-year-old female using a stereo lithographic technique. This type of modeling can be used in biomedical research, patient education, and training of medical students. Surgical training is one of the fields that have benefited from 3D printing technology. Rose and coworkers investigated a temporal bone model using the SLA technique of 3D printing using multiple colors and materials (Hootan Mehraein, 2018).
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