As known, many high-tech objects demand fine working parts and even finer details—such as the silent switch on the iPhone—it is still difficult to compete with the high precision capabilities of certain manufacturing processes, but time will prove this technology in every case. In every case, 3D printing is changing business model innovation in a very rapid manner Figure 2 [ 7 ]. Available technologies and materials for 3D printing and lamination techniques.
Polymers in Defence and Aerospace Applications 2010
Source: www. This part refers to the main 3D printing technologies which enable us in printing layered structures in some detail. Only the principal ones in use nowadays are reported, and some innovative ones are shown in the applications chapter. The FDM printing process begins with a string of solid material called the filament.
This line of filament is pulled from a reel attached to the 3D printer to a heated nozzle inside of the 3D printer that heats the material above its melting point. Once in a melted state, the material pushed out of a nozzle is extruded on a specific and predetermined path guided by the software on the computer usually instructed in G-code language. As the material is extruded, as a layer of the object on this path, it instantly cools down and solidifies—providing the base for the next layer of material until the entire object is manufactured.
Considered nowadays as the cheapest 3D printing technology commercially available, FDM also offers a wide variety of plastic-matrix materials in a rainbow of colors including ABS, PLA, nylon, and blends with more exotic materials, including carbon, bronze, or wood Figure 3. FDM is a considered to be the most practical choice for quick and low-cost prototyping. It can be used for a wide range of applications and objects with a typically wide palette of polymers as filaments in pure or reinforced form. Recently, FDM 3D printing has become very famous among hobbyists for enabling them to design and produce functional products, with embedded electronics and mechanical parts such as drones.
Polymers in Defence & Aerospace Applications 2nd International - Google книги
FDM 3D printing is hampered by design and material limitations, although improvements appear almost continuously nowadays. The technology generally is not considered suitable for more intricate designs or where high strength is required [ 8 ]. Usually, the parts manufactured with this technique can exhibit some internal anisotropy due to layering procedure [ 9 ]. These techniques are reported together, due to the fact that both technologies produce 3D-printed parts using a photo polymerizing polymer resin, featuring a UV light source to cross-link the liquid material [ 10 ].
Analytically, the procedure is as follows: a building platform submerges into a translucent tank vat filled with the liquid photo polymerizing resin. After submerging the tank, the UV light source located inside the machine, focuses through the bottom of the tank, scans each layer of the object, effectively solidifies-crosslinks, or polymerizes the material in other words.
Consequently, the platform is lifted upward by a few microns, thus allowing a fresh layer of resin to flow beneath the object. The UV light source shall map and solidify the new layer onto the previous one. Micron-by-micron step, the process is repeated in a layer-by-layer fashion, top to bottom until the whole part is finished. The progress made in the past decades delivered enabled 3D printing processes to be applied in desktop 3D printers.
Needless to mention here, materials selection is limited to UV-crosslinked polymers. The materials selection, however, broadens each year, new resins with enhanced strength or flexibility are available on the market. This makes them especially famous among artists, for manufacturing sculptures, jewelry molds, and other prototypes. The technology has been accessed as a useful tool in biomedical engineering too [ 11 ] Figure 4. In the process called selective laser sintering SLS , a high-power laser is required.
Advanced composite materials (engineering)
The laser is employed in order to melt and solidify layers of powder and produce, again layer-by-layer, 3D objects. The SLS printers are commonly equipped with two plates called pistons. First, a first layer of powder is laid onto the fabrication piston. In this way, the first layer is fabricated. After solidification of the first layer, the fabrication piston is slightly lowered, and the powder delivery bed, in which the power is contained, is raised by some microns.
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Then, a roller forces another layer of powder on top of the previous solidified layer. The aforementioned procedure is repeated, allowing the laser to melt and solidify all successive layers one by one, until the designed part has been finished bottom to top Figure 5. Selective laser sintering SLS method. SLS is a highly efficient method, though rather expensive, but has established itself into the industrial 3D printing applications. Desktop SLS printers are widely available on the open market, and prices are already quite affordable. The usual materials available nowadays as powders for SLS include most thermoplastics such as polyamides nylon , polystyrene, thermoplastic elastomers, etc.
Due to its high accuracy and production fidelity, SLS machines are widely used for manufacturing end products as well as functional prototypes. Complete design freedom is its most important advantage. There is no need for support of structure.
The surrounding unmolten powder acts as a support for the structure as it is layered, which allows for complex, sophisticated, and delicate shapes to be manufactured. Finished objects, as a side effect, take a bit more time to cool, and thus longer lead times are expected. Excess and attached object powder is removed by blowing air or using high pressure water or liquids, and is recycled after filtering; hence, economy of raw materials is in situ achieved.
They are considered as offspring of the SLS technique described above. Just like SLS, these processes create objects from thin layers material. Raw material is the form of powder and it is selectively melted using an intense heat source. As metals and also ceramics, are characterized by higher melting points, consequently much more power is required; this is provided by a high-power laser for SLM or even an electron beam in the EBM technology.
The printing process begins by distribution of a thin layer of metal powder onto a build plate. The platform or build plate is afterwards lowered by some microns and rapidly coated with new layer of metal powder on top of the solidified layer. The process is repeated until all layers have been solidified resulting in the finished part.
see url Contrary to SLS, the SLM and EBM techniques require support structures, in order to stabilize the object to the build platform and enable manufacturing of overhanging parts. As a side effect, these enable heat transfer away from the solidified powder. These conditions enable thermal stresses reduction and warping prevention, and they also allow reactive metals and alloys to be used as raw material. Materials include various metals and alloys including steel, titanium, aluminum, cobalt-chrome, and nickel.
SLM and EBM have evolved to a stage where these prints are directly comparable to traditionally manufactured parts in terms of chemical composition, mechanical properties static and fatigue , as well as microstructure.
A stainless-steel bracket optimized for weight reduction front and the traditional cast bracket in the back. Source: European Space Agency events via Flickr. BMW wants to help accelerate the rollout of this technology in both its design and manufacturing departments. In the same spirit, Swedish car manufacturer Koenigsegg employed 3D printing to manufacture the variable turbocharger for their One:1 model—a car that has an astonishing HP-to-Kg curb weight ratio. The company often services customers with Lamborghinis, Ferraris, and classic Bentleys, so the fit and finish on the OEM-grade thermoplastics has to be perfect.
BMW, as mentioned above, went for 3D printing technologies quite early. BMW is considered to be of the founding fathers of stereolithography having recently revealed plans and approach for a fully 3D printed car. One can understand how deeply 3D printing has become incorporated into the company culture by the fact that even a thumb cast for assembly line workers was produced in that way. Evidently, the workers have to push by thumb, a huge number of rubber plugs into chassis holes on the assembly line. This repetitive work causes a repetitive strain type injury in many of them. Confronting the issue, BMW engineers came up with a bright idea: a cast of the thumb and hand that relieved all the strain out the process.
Quite simple, very brilliant, and it just proves just how deep 3D Printing has gone into the corporate culture at BMW. It also shows that 3D printing goes beyond the actual manufacturing process itself into biomechanics and ergonomic concepts Figure 7 [ 15 , 16 ]. BMW has turned to 3D printing to augment its workers and stop strain on limbs frequently found on manufacturing lines.
Photograph: BMW republished from the Guardian. Being always at the cutting edge of technology, biomedical and prosthetics fields has largely benefited from the introduction of 3D printing in these sectors.
Custom-shaped personalized-hearing aids no longer require manual labor to manufacture; with 3D printing, they can be made with the click of a button in a very short time. This of course implies substantially lower costs and shorter production times. Even orthopedic implants manufacturing at custom dimensions from CT or MRI scans from the patients is nowadays feasible. Prosthetics and other assistive medical devices, braces, and retainers are tailored specifically for the needs of the patient.
This has totally reversed an inherent problem that of time and energy required to manually produce each product. As a natural consequence, introduction of 3D printing in the dental and orthodontics fields was an inevitable event.