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Additive Manufacturing.
Additive manufacturing is defined as the process of producing the parts or components by depositing the material layer -by -layer, using 3D computer data or standard tessellation language (STL) files which contains the data regarding the geometry of the object.
Additive manufacturing is defined as the process of producing the parts or components by depositing the material layer -by -layer, using 3D computer data or standard tessellation language (STL) files which contains the data regarding the geometry of the object.
“Additive manufacturing, also known as 3D printing, is a transformative approach to industrial production that enables the creation of lighter, stronger parts and systems.”
Additive manufacturing (AM) processes fabricates components using 3D computer data or standard tessellation language STL files which contains the data regarding the geometry of the object. 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.
Although the terms “3D printing” and “rapid prototyping” are generally used to discuss additive manufacturing, each process is actually a subset of additive manufacturing.
SpaceX:
SpaceX the first private company to launch an orbital rocket uses the additive manufacturing technology to optimize their processes and produce parts that aren’t possible with conventional methods of manufacturing.
SpaceX uses vertical integration, in which the raw material is brought at one end of the factory and a fully manufactured rocket comes out of the other end. Additive manufacturing allows the implementation of this philosophy by eliminating the typical process involved in a cast part where a complex mould is manufactured followed by a test casting at the foundry with necessary follow-up alternations to mould and post-processing. Adaptation of additive manufacturing reduces the cost, allows for stricter quality control and reduced lead times.
SpaceX makes use of direct metal laser sintering.
Solid Based Additive Manufacturing
Fused Deposition Modeling (FDM):
This is one of the most widely used technique in AM for fabricating prototypes and functional parts in common engineering plastics. Heated feedstock plastic filament is extruded through a nozzle tip to deposit the material layer by layer onto the platform following the digital model of the part which is generally a CAD file.
The simplicity, reliability, and affordability of the FDM process have made the additive manufacturing technology widely recognized and adopted by industry, academia, and consumers. FDM is widely being used by the research and development sector to improve the process, develop new materials. FDM systems finds its wide range of usage in engineering applications.
*This is one of my personal favorite methods.
Laminated object manufacturing:
In this process, a continuous sheet of the build material is drawn across the build platform by a system of feed rollers, for plastic and paper kind of build materials the sheets may be coated with adhesive. A heated roller then passes over the material, melting the adhesive and pressing the material down onto the platform. A blade or a laser cuts the desired pattern into the material and crosshatches the unused material so that it can be removed later. A take-up roll winds up the remaining material. Finally, the build platform drops down the thickness of one layer, new material is pulled across the platform and the process is repeated.
The components fabricated by LOM include a high surface finish, low material requirement, lesser machine and process costs, and high strength.
This process has limited 3D geometries compared to other Am process. The solidity of the object is highly dependent on the type of resins and curing process used. The resins are limited to those objects made using paper or plastic. Metal sheets are welded (either thermal brazing or ultrasonic welding) or bolted together to form the part. The use of metal in the LOM process is rare.
Direct ink writing or Robocasting:
This technique consists of the robotic deposition by extrusion of a paste filament - ‘ink’ as per the analogy with conventional printing, from a small nozzle. The ink consists of a highly concentrated ( 35 – 50 vol %) of colloidal suspensions of ceramic powders typically in water, which are capable of supporting their own weight during assembly, whose rheological properties are carefully tailored to flow through the nozzle and have an excellent shape retention capacity upon deposition.
They exhibit shear-thinning behavior, the ink behaves as a pseudo solid after deposition and the shape retention does not rely on the solidification or drying of the feedstock as in other techniques.
Freeze form extrusion fabrication
This method has been developed for the fabrication of ceramic-based components, this an environmentally friendly solid freeform fabrication. This method is based on the deposition of ceramic pastes using water as the media, the organic binder content is only 2-4 vol% in this process, while the ceramic solids loading of the paste can be 50 -60 vol%. .This is possible by performing the deposition within a freezer. The lower temperatures allow the slurry to maintain its shape by freezing the water present in the slurry The FEF setup is composed of five major components: the motion system, control system, deposition device, force sensor, and freezer.
Liquid-Based Additive Manufacturing
Stereolithography:
In this method, a high powered laser is used to harden the liquid resin which gets solidifies when hit by the low power laser, the liquid resin is contained in a reservoir to create the desired 3D shape. The photosensitive liquid is converted into a 3D solid plastics in a layer – by – layer fashion using a low – power laser and photopolymerization.
The laser draws the layers of the print into the photosensitive resin whenever the laser hits the liquid, it solidifies. The laser draws the first layer of the print into the photosensitive resin, the liquid solidifies whenever it is hit by the laser. The laser is pointed up to the build platform which starts low and is incrementally raised., most desktop stereolithography printers work upside-down.
After the first layer is solidified the platform is raised according to the layer thickness – about 0.1mm, and the additional resin flows below the solidified portion, the laser then solidifies the next cross-section, and the process is repeated until the whole part is completed. The resin that is not solidified remains in the vat and can be reused.
*this another favorite method of mine.
Rapid freeze prototyping:
This is a novel solid freeform fabrication technique that generates the 3D ice objects using layer by layer deposition of rapidly freezing water. The necessary support structures are made of brine whose freezing point is lower than the pure water. The support can be removed by unitizing the melting temperature between the brine and water.
Uses part visualization, Ice sculpture fabrication, silicon moulding, investment casting.
Multi-jet modeling:
A UV curable polymer is deposited using multiple nozzle jets. When the polymer gets out of the head UV lamp flashes to cure the material. The parts are a printed on a moving platform that moves down after the current layer is cured, it is a very cost-effective technique, The process is quite and safe and can be done in a laboratory environment and it can fabricate the parts in a very quick time frame.
Digital light processing:
The image of the 3D model is projected on to the polymer, which hardens on the exposure and the build plate moves down and the liquid polymer is once more exposed to the light. This process is repeated until the 3D model is complete. This method is faster and can print objects with a higher resolution. This method is similar to stereolithography in the sense that it utilizes the photopolymers but the primary difference lies in the light source – a conventional light source – arc lamp and a digital light projector is used.
Powder Based Additive Manufacturing
Inkjet 3D Printing or Binder jetting :
In this method, a liquid binder is utilized to bond the powder materials. The powder layer is spread on the build platform and the binder liquid is extruded through nozzles. This method does not require an additional support structure
Powder Based Additive Manufacturing
Inkjet 3D Printing or Binder jetting :
In this method, a liquid binder is utilized to bond the powder materials. The powder layer is spread on the build platform and the binder liquid is extruded through nozzles. This method does not require an additional support structure
Electron beam melting :
This method utilizes an electron beam in a high vacuum as the heat source to consolidate the metal powder into a solid mass. The metal powder is spread over the bed in the layer by layer form which gets sintered by the electron beam. As the process takes place under a high vacuum, it is suitable to manufacture parts in reactive materials with a high affinity for oxygen like titanium. This process is known to operate at very high temperatures up to 1000 degrees celsius which leads to a difference in phase formation through solidification and solid-state phase transformation.
Selective laser sintering and selective laser melting :
Selective laser sintering involves the use of a high power laser to fuse the small powdered particles of metal, ceramic, glass or plastic into a mass that has the desired 3D – shape. The laser selectively fuses the powdered material by scanning cross-section generated from of 3D- model. The powder bed is lowered after each cross-section and the new material is applied on the top.
Selective laser melting is similar to selective laser sintering in the procedure but in SLM the material is fully melted rather than sintered, allowing different properties like crystal structure and porosity.
*This is another one of my favorite methods.
Laser engineered net shaping :
A high power laser is used to melt (weld) air blown streams of metal powder supplied coaxially through nozzles to the focus of the laser beam. A laser beam melts the top layer of the part in areas where the material is to be added, while powder metal is injected into the molten pool, which then solidifies. Layer after layer is added until the part is complete. The resulting parts have exceptional mechanical properties. This technique produces shapes close enough to the final product to eliminate the need for rough machining. One of the purposes of LENS is to make small lots of high-density parts or mould. The laser beam typically travels through the center of the head and is focused to a small spot by one or more lenses. The table is moved along the X and Y axes and the head is moved up vertically after each layer is completed.
Metal powders are delivered and distributed around the circumference of the head either by gravity or by using a pressurized carrier gas. An inert shroud gas is often used to shield the melt pool from atmospheric oxygen for better control of properties, and to promote layer to layer adhesion by providing better surface wetting. This is a complicated operation because high temperatures make it difficult to form accurate, smooth objects from molten metals. Materials like Titanium alloys, nickel-based alloys, metal matrix composites, steel, aluminium etc, can be employed for this process. The extreme rapid cooling in this process generates a fine-grained microstructure, producing high tensile strength and high ductility.
Laser metal deposition :
This unique technique, combining laser and powder processing, enhances the material utilization by enabling the manufacture of high precision near net shape components from powders.T he laser beam forms a pool of molten metal on the surface of the metallic substrate. A nozzle of multiple nozzles blows the metal powder into the process zone where the laser beam preheats the particles which are absorbed into the laser-induced molten pool. The absorbed metal powder produces a deposit on the surface. Typical applications include the repair of metallic components, such as mould tools, valves, worm screws.
The aerospace industry has been exploiting the usage of AM for its obvious benefits over traditional manufacturing techniques. The application includes the manufacturing heat resistant functional parts of engine compartments, air ducts using SLS, cabin accessories, size panels – seat backs & entry doors with standard resin by SLA.