Study of Composites Materials from Waste for Large-Scale Additive Manufacturing ^†

With the development of large-scale additive manufacturing (LSAM), parts can be created with higher deposition rates and bigger build volumes. Thus, it is important to develop alternative feed-stock that can be made with waste fillers to sustainably expand the raw materials that can guarantee the production of parts with similar accuracy and properties. The purpose of this study is to evaluate the processability of non-conventional and chemically treated composite materials for their use in the LSAM process. Polypropylene blends were prepared with starch, sawdust and calcium carbonate fillers. The fillers surfaces were pre-treated in acidic and basic chemical medium. The incidence of particle diameter, chemical pre-treatment and amount of plasticizer on the mechanical response of injected specimens was evaluated. The incidence of process variables in large scale additive manufacturing using an extruder mounted on a robotic arm was evaluated through the quantification of geometric deviation and warping of parts printed with the different composite mixtures. An improvement in mechanical properties was evident for those fillers that were chemically treated in a basic medium over those in an acid medium. Wood waste composites had the closest mechanical properties to those of the matrix alone. Calcium carbonate composites showed the widest range of processability as well as the best thermal stability, which was evidenced by the lowest geometrical deviation and warping. It was determined that the print bed temperature is the factor that has the greatest incidence during the first 6–7 layers of the printing. From this point on, the temperature of the environment has the greatest impact on the performance of the process.