## 3 Additive Manufacturing of Pla-Metal Biodegradable Composites  
For the manufacture of the PLA-Metal biodegradable composites, the FDM technique was the most commonly used method. The FDM technique works on the principle of building a solid object through layer-by-layer deposition of the melt filament fed via a nozzle on a platform heated to a certain temperature to enhance the solidification rate of the 3D printed part. This method could handle PLA-based filaments with reinforcements in fibrous (long and short), and particulate forms. Figure 8 depicts the schematic of the FDM technique. Researchers prepared PLA-Mg filaments for various biomedical applications and manufactured the films using the AM technique. After preparing them as films, the extruder chopped the PLA/Mg composites in varying concentrations into even-sized squares. In this case, the most cutting-edge filament extruder was a Filabot EX2 system. The system employed melt-integrating extrusion, operating at an average temperature of 175 \({}^{\circ}\)C, to push the filaments through a 0.2 mm nozzle. The filament that had been extruded was subsequently ground into tiny, even pieces and put back into the extruder to confirm that the Mg particles had been consistently distributed. Subsequently, the filaments were utilized with different amounts of magnesium for additional research and 3D printing [46]. Few studies have used PLA-Zn-based composites and used AM techniques to manufacture composites. The process maintained a 100% infill density and a concentric infill pattern. The first layer thickness is 0.3 mm, whereas the subsequent layer thickness is maintained  
Figure 8: Schematic of FDM technique [67]. as 0.2 mm. The first layer is printed with a 30 mm/s speed, whereas the layer print speed is maintained at 80 mm/s. The nozzle temperature is set at 230 \({}^{\circ}\)C, while the bed temperature is maintained at 60 \({}^{\circ}\)C. We set the build orientation along the x-y plane in a flat configuration. The nozzle diameter was set to 0.4 mm for seamless printing [68]. It was stated in various studies that the AM techniques could process complicated parts with accurate dimensions at the lowest feasible cost; FDM has seen extensive use in additive manufacturing. Materials used in FDM, like PLA, have low melting points because of the technology's limited working temperature range. The problem with FDM-printed thermoplastics is that they do not have the mechanical strength or properties needed to print functional parts, like thermal and electrical conductivity. These problems have led to the development of a novel composite material for the FDM technique. Investigation performed on the flexural properties of polymer-matrix composites (PMCs) with varying amounts of copper reinforcement (25 wt. % and 80 wt. %) using various infill designs. The study focuses on examining the differences in input velocity variables between PLA and PLA/Cu composite filaments. The study introduces a numerical model of a nozzle and uses finite element analysis to examine the behavior of the melted filament fluid. The study thoroughly examined the flow characteristics, including pressure, melting temperature range, and velocity. Next, tests were conducted to determine the optimal printing velocities for the two filaments [69]. Changing the filament feed velocity causes a corresponding change in the flow parameters, according to the results. Lastly, the ideal input velocity for PLA is from 2 to 3.5 mm/s, while for PLA/Cu, it is less than 5 mm/s, as determined by the assessment of printed specimens' dimensional accuracy [70]. A readily accessible PLA/Cu filament was 3D printed employing the FDM technique. The tensile properties of this filament were the primary focus of this investigation. Printing orientation and fill pattern, along with infill density, were among the many parameters for printing tweaked to achieve this goal [71]. Usually, 3D-printed samples are tested for strength to see how the printing settings affect the strength of the printed parts.