Core shell nozzle6/11/2023 Another polymer resin with a low glass-transition temperature, such as Surlyn or high/low density polyethylene, is used as the shell to enable improved interdiffusion of polymers between adjacent layers. In this approach, a polymer resin, favouring from the high glass-transition temperature, such as polycarbonate (PC) or a blend of PC and acrylonitrile-butadiene-styrene (ABS), acts as the core to create a stiff skeleton, reinforcing the printed shape. To overcome some of the mentioned drawbacks, a novel material design approach, namely core–shell structured filament, has recently been developed. Such imperfections have necessitated the improvement of materials used in ME-AM printed parts to ensure that the structural functionalities of fabricated components comply with the functional requirements of different applications. This weakness hampers the development of ME-AM from a prototyping role to a process capable of manufacturing finished products. Besides, the inherently inferior mechanical properties of filaments, commonly used in ME-AM, exacerbate the position of fabricated parts as fully functional and load-bearing components. ![]() Furthermore, layer-based manufacturing methods suffer from rough surfaces, whose post-processing is laborious compared to that of metals. Nonetheless, because of the layer-by-layer nature of the deposited material and the existence of numerous voids, parts fabricated by ME-AM suffer from inferior mechanical properties, e.g., low elastic behaviour, possible delamination, and low mechanical integrity. In the ME-AM process, 3D parts are formed through the controlled deposition of successive layers of molten material extruded from a moving head along a predefined toolpath. The reason for this attention is its relatively low cost, wide availability, comparatively minor safety concerns regarding the process, and ease of use. Among different technologies, material extrusion AM (ME-AM)-also termed Fused Filament Fabrication (FFF), or Fused Deposition Modelling (FDM)-has been gaining interest. Overall we find that the best operating parameters are a diameter ratio of d / D = 0.7, a normalised gap of t / D = 1, and a velocity ratio of V / U = 1.Īdditive manufacturing (AM) has introduced several advantages over conventional methods, such as shortening the design manufacturing cycle, lowering production costs, and increasing the degree of automation. Numerical results of the deposited strands’ cross-sections demonstrate the effects of controlling parameters on the encapsulation of the core material inside the shell and the shape and size of the strand. In this model, the deposition flow is controlled by three dimensionless parameters: (i) the diameter ratio of core material to the nozzle, d / D (ii) the normalised gap between the extruder and the build plate, t / D (iii) the velocity ratio of the moving build plate to the average velocity inside the nozzle, V / U. At the same time, complete encapsulations are obtained for the core polymer inside the shell one. The objectives of these CFD simulations are to find strands with an ultimate volume fraction of core polymer. Here we use numerical simulations within the framework of computation fluid dynamics (CFD) to identify the best combination of operating parameters for the 3D printing of a core–shell polymer strand. ![]() Operating parameters play an important role in forming the overall quality of the 3D-printed manufactured products. Using ME-AM for core–shell manufacturing offers improved mechanical properties and dimensional accuracy over conventional 3D-printed polymer. Material extrusion additive manufacturing (ME-AM) techniques have been recently introduced for core–shell polymer manufacturing.
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