Fused filament fabrication (FFF), also known by the Stratasys trademark fused deposition modeling (FDM), is one of the most popular additive manufacturing techniques for the production of polymeric components. The production of metallic and ceramic components by FFF is also possible and offers great advantages such as the wide range of materials available, as well as a low cost of the equipment as compared to other techniques. The FFF of metals and ceramics is conducted in a three-step process known as shaping-debinding-sintering (SDS). In the SDS process, polymer compounds (known as binders) are highly filled with powder of a ceramic or metallic material (obtaining the feedstock). The function of the binder is to act as a carrier, enabling the shaping of the powder by FFF. Once the parts are shaped, the polymers are removed in the debinding stage first by leaching with a solvent of the major binder fraction and thermal decomposition of the rest using the existing pores. Finally the parts are sintered at temperatures lower than the melting point of the material. A large shrinkage occurs, which must be considered in the design of the parts.
In the project CerAMfacturing, the production of new multi material parts by FFF is being developed [1]. An infrared heater has being chosen as demonstrator, requiring electrical conductivity and insulating functionalities by the combination of metallic and ceramic materials. New binder formulations have been developed (considering the requirements for FFF and SDS [2]) and tested for the production of such components. For feedstocks containing powders with small size, such as those of the zirconium oxide used as insulating material, large defects were observed after the immersion in cyclohexane. In addition, the debinding rate is considerably smaller than those of other powders with larger size such as stainless steel or titanium [3]. In order to facilitate the debinding process, stearic acid (SA) has been incorporated as a surfactant [4]. The improvement of the dispersion of the powder and the smaller swelling of the SA during its dissolution facilitates the process and increases the debinding rate while reducing the defects observed in the parts. Nevertheless, these defects can be still observed, and further optimization is required in both the formulation and the process.