33 Polymer considerations for EV | Focus produces new plastics. The added benefit of this approach is that, if any materials do get into the environment despite this closed loop, they can biodegrade without any lasting impact. 3D printing Thermoplastics are changing the options with additive manufacturing, or 3D printing. The latest highperformance, polyamide-based composite reinforced with carbon fibre has a density of 0.87 g/cc (grams per cubic centimetre), particularly for lightweight electric aircraft designs. This is used with powder-bed fusion or selective laser sintering (SLS), where a high-power laser heats the granules to create functional prototypes and components with a balance of lightness, stiffness and thermal resistance. The heat deflection temperature (HDT) is a critical property for 3D-printing materials, especially when using fused deposition modelling (FDM). It is an important consideration because the material is heated and melted to create a 3D object, and the HDT of 1.82 megapascals (MPa) of 182.5 C for the polyamide material provides high values of specific tensile and impact strength. The post-process surface finish is key for smoothness for aerodynamics. The surface roughness (Ra value) is 5.44 µm after the SLS process, 1.56 µm after manual finishing, and 0.83 µm after CNC processing, ensuring smooth and precise surfaces. 3D-printing thermoplastics are also being used for the load-bearing frame of an electric cargo scooter with a new technique. SEAM (screw extrusion additive manufacturing) technology was used to produce the shelf and frame. A custom 3D-printing process is eight times faster than conventional methods, but it also processes cost-effective, standard plastic granules. Compared with conventional fused-layer modelling (FLM) processes, which use expensive filaments, production costs are up to 200 times lower. SEAM technology was used to manufacture the shelf and frame construction of the scooter. The printing process is carried out by drawing plastic granules into the extruder using a modified extrusion screw and plasticising them. A material output of up to 10 kg per hour can be achieved, and the resulting plastic melt is deposited in layers on the construction platform. The continuous storage process makes it possible to produce large-volume, resilient components. The granules can be obtained from recycled thermoplastics. A concept e-vehicle has also been developed with 3D-printed thermoplastics to explore new designs and construction techniques. The materials and 3D printing changed the way the cars were manufactured, and made it possible to change not only the design but also the form of the vehicle by constructing a modular structure of interior and exterior parts. The design has an external battery pack, which expands the range of platform options to include a mobile shop, a truck, a flat cabin/luggage space that is easy to use and clean, and removable interior and exterior parts. Coatings and acoustics As well as the structural and light weight requirements, the ability to apply various coatings to the thermoplastic is vital for several reasons. While the EMI shielding is, of course, a major requirement, so are the vehicle acoustics. For a vehicle’s occupants, the focus is on noise reduction. While outside the vehicle, the focus is on safety, E-Mobility Engineering | March/April 2024 3D-printed vehicle measures 2,955 mm x 1,475 mm x 1,590 mm. The wheel base is 1,985 mm (Image courtesy of Daihatsu)
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