37 long or short carbon fibres, one particular end-effector can apply the carbon fibre precisely where specified by the design software. By reinforcing only where necessary, this creates lightweight, strong thermoplastic parts at a much lower price compared to current carbon fibre manufacturing technologies. Another end-effector can use a newer technique called AMCompression Moulding (AMCM). This uses a short fibre-filled polymer and a continuous fibre polymer to print directly onto a mould with precise orientation to make parts such as propeller blades or battery boxes. Compression moulding then turns the print into an accurate finished piece. This significantly reduces the time and cost by producing 100 parts in 5 hours compared to layer assembly, with each piece taking less than 3 minutes to print. Combining the fibre control of an additive process with the low porosity of compression moulding enables high-volume production of lightweight composite materials for more energyefficient designs. Magnets One area of development is to reduce the size and weight of magnets that can be produced using AM. Finding the optimal conditions for 3D-printing permanent magnets fromhard magnetic compounds based on rare earth metals will allow small-scale production of magnets of any shape, and create complex configurations of them. Using 3D printing to produce them reduces waste and has a shorter production cycle; suchmagnets are suitable for miniature electricmotors and generators. Creating complex and small magnets for sensors for example is not an easy scientific and technical task, but they are in demand for various specialised applications. One of the most promising ways to create complex-shaped parts frommagnetically hard materials is to use selective laser sintering. This is an AMmethod where the magnetic material in the form of powder is sintered layer by layer into a 3D product of a given shape based on a previously created 3Dmodel. The technology makes it possible to change the internal properties of the magnet at almost any stage of production, such as changing the chemical composition of the compound, the degree of spatial orientation of the crystallites and crystallographic texture, and to influence the resistance to demagnetisation (the coercivity). Small magnets are currently created by cutting a large magnet into pieces, but because of the mechanical processing about half of the material used is waste. Cutting also introduces defects in the near-surface layer, which causes the properties of the magnet to deteriorate. Additive technologies avoid this and allow more complexmagnets to bemade, such aswith one north pole and two spatially separated south poles, or amagnet with five south poles and five north ones. The latest permanent magnets are about 1 mm thick and are made from a powder containing samarium, zirconium, iron and titanium. The compound has suitable characteristics for permanent magnets, but traditional manufacturing methods eliminate most of its properties. When sintering a sample, adding a fusible powder from an alloy of samarium, copper and cobalt allows the magnetic characteristics of the main magnetic powder to be retained. The alloy melts at lower temperatures than those at which the properties of the main alloy change, which is why the final material retains its coercive force and density. Peristaltic pump Researchers have also 3D-printed a miniature vacuum pump that uses a peristaltic mechanism. The pump can create and maintain a vacuum as low as 9 Torr (about 1200 Pa), an order of magnitude lower than other types of commonly used pump, with a 10 standard cc/minute flow rate. The design, which can be printed in one pass on a multi-material 3D printer, prevents fluid or gas from leaking while minimising heat from friction during the pumping process. This increases the device’s lifetime. The pump uses a novel actuator design with a notched cross-section that requires less than half the force of other types of pumps to fully seal, making it possible to create and maintain low vacuum at low actuation speed. The device is made using multimaterial extrusion. The rigid parts of the pump are made from polylactic acid, while its compliant parts are made from FiberFlex 40D – a relatively new flexible material that is easier to print than mainstream Ninjaflex, even though the two materials have similar hardness. FiberFlex 40D also has good chemical compatibility with substances such as oil, butane and ethyl alcohol. Characterisation of the 3D-printed Additive manufacturing | Focus Uncrewed Systems Technology | June/July 2023 Additive manufacturing allows reductions in the size of motor magnets (Courtesy of MIT)
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