Abstract
Material extrusion additive manufacturing (ME-AM) techniques have been recently introduced for core–shell polymer manufacturing. Using ME-AM for core–shell manufacturing offers improved mechanical properties and dimensional accuracy over conventional 3D-printed polymer. Operating parameters play an important role in forming the overall quality of the 3D-printed manufactured products. 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. The objectives of these CFD simulations are to find strands with an ultimate volume fraction of core polymer. At the same time, complete encapsulations are obtained for the core polymer inside the shell one. In this model, the deposition flow is controlled by three dimensionless parameters: (i) the diameter ratio of core material to the nozzle, ; (ii) the normalised gap between the extruder and the build plate, ; (iii) the velocity ratio of the moving build plate to the average velocity inside the nozzle, . 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. Overall we find that the best operating parameters are a diameter ratio of , a normalised gap of , and a velocity ratio of .
Highlights
Additive 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 [1,2]
In the material extrusion AM (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 [4,5]
A manufacturing process in which the core polymer embedded into the shell inside the heated printing head and the resulting core–shell structure immediately deposited onto the build plate was simulated
Summary
Additive 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 [1,2]. Material extrusion AM (ME-AM)— termed Fused Filament Fabrication (FFF), or Fused Deposition Modelling (FDM)—has been gaining interest. The reason for this attention is its relatively low cost, wide availability, comparatively minor safety concerns regarding the process, and ease of use [3]. 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 [4,5]. 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 [6,7]. Layer-based manufacturing methods suffer from rough surfaces, whose post-processing is laborious compared to that of metals [8,9]
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