Material extrusion (ME), sometimes called Fused Deposition Modeling (R) or Fused Filament Fabrication, is an additive manufacturing technique that places order 300 mu m diameter molten polymer filaments sequentially onto a moving substrate to build an object. The feed material is a solid fiber that acts like a continuous piston in a heated barrel, which plasticates itself to push molten material through a nozzle. The barrel pressure is substantial, of order 30 MPa (approximate to 4000 psi), and similar to that developed in contemporary polymer processing. The similarity does not end here with all the non-Newtonian and viscoelastic effects and heat transfer limitations that challenge extrusion operations coming to bear in the ME. These will be discussed in this review with suggestions of areas of study. (C) 2018 The Society of Rheology.
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