Fused deposition modeling (FDM) is one of the leading emerging technologies of Industry 4.0, which has been employed to develop sustainable engineering products, customized implants and sophisticated biomedical devices. However, the mechanical strength and durability of 3D printed parts is still lower than its conventional counterparts, which restrict its widespread use. In this regard, the use of short fibres (i.e. natural or artificial) and advanced nanomaterials to reinforce the existing polymer matrix has been drastically increased to improve the load bearing capacity of FDM printed parts. Hence, this article aims to provide a systematic review on thermoplastic composite structure prepared through FDM technology and summarizes the current knowledge about the use of various additives to improve the overall quality FDM parts. Moreover, the common defects associated with FDM printed composite structures and the methods required to improve the quality of FDM composite parts are discussed in this article.

Hailed since the fourth industrial revolution, three-dimensional (3D) printing or additive manufacturing (AM) has been extensively implemented in various manufacturing sectors. This process is popular for generating regular products and incorporating innovative designs into the components like auxetic structures, such as fabrication of engineering products, customized implants and sophisticated biomedical devices. Over the years, one of the interesting outputs of this emerging technology is the reuse of waste thermoplastic materials to produce competent products through the fused deposition modeling (FDM) technique. The strength of FDM components produced from thermoplastic waste is lower than that of virgin plastic FDM counterparts. So, there is a need to understand the significant changes in the recycled thermoplastic material during subsequent extrusions, which are chain scission, change in viscosity and breaking strength. The use of additives has been a promising solution to improve the performance of recycled material for 3D printing applications. Hence, this study aims to provide an overview of reusing plastic waste through FDM-based 3D printing. This review summarizes the current knowledge about the effect of processing on thermo-mechanical properties of recycled plastic FDM parts and the use of various additives to improve the overall quality. In addition, two case studies from open literature have been demonstrated to explain the use of FDM and associated technology for plastic recycling.

Waste plastic exposed to the environment creates problems and is of significant concern for all life forms. To reuse the waste plastic in a well-organized manner and make it more productive, extrusion-based additive manufacturing, specially fused deposition modeling technique, can be an effective way. Hence, the primary objective of this work is to reuse ABS waste for developing sustainable three-dimensional printing filaments. A mixed feedstock processing approach is used to develop filaments, in which recycled ABS is blended with virgin ABS in weight ratio of 10%-50%. The rheological and thermomechanical properties of the extruded filaments were examined. Results indicated that increasing extrusion temperature from 190 C to 195 C produced significant physical changes in ABS blends. There is a breakdown of styrene acrylonitrile and butadiene component in ABS which causes strain hardening and material stiffening. The Young's modulus, yield strength and ultimate tensile strength of 80% RABS/20% VABS filament were found to be 2329, 34.814 and 40.82 MPa, respectively, which is close to VABS filament. The novel filament produced from recycled/virgin ABS blends has the capability to replace commercially available ABS filaments for fabricating high-quality plastic parts through an additive manufacturing routine.

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Glass-filled polyamide (GF/PA) is an important engineering material for automotive industry because of its excellent physical, thermal and mechanical properties. But it is challenging to produce high quality functional parts through additive manufacturing technology like selective laser sintering (SLS). It is due to fact that SLS made parts exhibit high dependence on the sintering conditions. Thus, it becomes essential to adjust these sintering conditions accurately to improve physical properties like density and hardness to enhance the widespread use of this technology. Therefore, this study presents a statistical analysis of the SLS process parameters led by a design of experiment to extract information about their influence on hardness and density of the PA 3200 GF composite. GF/PA with a refresh rate of 60:40 was used for the part fabrication and the effect of five key sintering parameters has been considered for analysis. Experiments revealed that poor material integrity and weak interaction between the particles at lower energy density were the main reason for the lower hardness and density of fabricated parts.