Avoiding loose powders and resins, material extrusion additive manufacturing is a powerful technique to produce near-net shape parts, being a cheap and safe alternative for developing complex industrial-grade products. Filaments embedded with a high packing density of metallic or ceramic granules are being increasingly used, resulting in almost fully dense parts, whereby geometries are shaped, debinded and sintered sequentially until the completion of the part. Traditionally, “brown” debinded geometries are transported to conventional furnaces to densify the powder compacts, requiring careful tailoring of the heating profiles and sintering environment. This approach is decoupled and often involves time-consuming post-processing, whereby after the completion of the shaping and debinding steps, the parts need to be transported to a sintering furnace. Here, it is shown that sintering via indirect induction heating of a highly filled commercially available filament embedded with stainless steel 316L powder can be an effective route to densify Fused Filament Fabricated (FFF) parts. The results show that densities of 99.8% can be reached with very short soaking times, representing a significant improvement compared to prior methods. A hybrid machine is proposed, whereby a custom-built machine is integrated with an induction heater to combine FFF with local indirect induction sintering. Sintering in situ, without the need for part transportation, simplifies the processing of metal parts produced through material extrusion additive manufacturing.

In-space manufacturing of polymer feedstocks has already been shown using the widely investigated filament extrusion additive manufacturing (AM) technology. Yet, polymers are only a small piece of the puzzle, and there is a growing demand to locally source metal and ceramic parts. In this manuscript, we propose a cost-effective method for in-orbit manufacturing of metal and ceramic multi-material components using highly packed powdered filaments, which need to be shaped, debinded, and sintered in sequential steps. Traditional debinding and sintering of material extrusion (MEX) AM parts are known to be time-consuming and require complex post-processing, often involving toxic debinding agents. To overcome this, a low-intensity infrared diode laser and an induction heater are coupled to a hybrid MEX system to allow full processing in situ, within the same volume. The results show that the main binder matrix can be removed across the 3D volume of the part via laser ablation of the polymeric mass, even for multi-material metal–ceramic composites. The sintered geometries further densify efficiently within the bulk due to the high-energy concentration of the induction sintering treatment, providing short processing times. Debinding and sintering locally, in the same machine, offer a simple and effective way to produce space hardware in situ, avoiding the use of consumables or part transportation to bulky equipment.

The traditional sintering of metallic components shaped via Material Extrusion Additive Manufacturing (MEAM) is a time-consuming process that involves sophisticated energy-intensive heating systems. This work describes a novel induction heater capable of efficiently tailoring temperature profiles to densify MEAM powder compacts. In situ sintering within the same device is achieved indirectly by heating a graphite crucible, whereby the heater is based on an inverter with a half-bridge topology using the Zero-Voltage Switching (ZVS) technique. The system comprises a bank of capacitors that, in conjunction with a work coil, form a parallel-topology resonant circuit. This design allows the inverter to be used as a current amplifier, thereby increasing its efficiency to deliver an output power of up to 5 kW. The device operates at a 62.86 kHz resonant frequency, achieving a 2.01 mm penetration depth and a 1365.7 °C crucible temperature with only 1.313 kW of consumption, providing an increase in efficiency compared to other low-cost systems. Equipped with a feedback circuit, it offers five distinct control techniques that enable the self-tuning of the crucible temperature. The results indicate that the Cohen–Coon tuning method is more robust compared to the Ziegler–Nichols, damped, no overshoot, and mixed techniques. Sintering with this novel induction heater provides an alternative method for reducing the processing times for MEAM geometries, paving the way for increased efficiency and reduced energy consumption. Circuit diagrams, simulations, and experimental data on the temperature, time, and output voltage are provided in this article.