###### Abstract
Then, adhesive drops of a liquid binding agent are ejected by an inkjet print header to selectively bond the powder particles and build a piece layer by layer [25]. Binder jetting of sand moulds for casting has a series of advantages, such as better resource utilization, increased production efficiency, and reduced carbon footprint [26]. Unlike classical thick moulds, the use of 3D printing offers great flexibility, allowing the fabrication of complex structures that would be difficult or even impossible to produce by conventional mould manufacturing processes. For example, lattice- or shell-type moulds with varying thickness have network-like structures that result in increased cooling rates and reduced sand consumption, mould weight, and production times [27; 28]. Another advantage is the possibility of using a multicomponent mould formed by the assembly of several parts to create the casting core and direct the molten metal in the desired filling direction. This was recently exemplified in the fabrication of a reduced-weight cellular structure made of an Al/Si alloy able to withstand several kN compressive and impact forces [29]. In BJ, several parameters affect the properties of the mould and, consequently, the final quality of the casted part. Among these, sand particle type and size, the sand/binder ratio, and layer thickness directly influence the printing resolution and surface roughness [30; 31]. Another important factor to control is the formation of entrapped gas defects during casting due to insufficient permeability of the porous network produced by BJ [32]. A high binder proportion results in a more rigid and resistant structure but produces a significant amount of gases during casting; hence, a balance between resistance and gas permeability should be reached. X-ray microcomputed tomography and numerical simulations were used to study the mass transport properties of sand moulds in different conditions. This permitted understanding and predicting gas permeability, among other factors, in order to optimize the casting process of 3D printed structures for foundry applications [33]. Some reports on the fabrication of aluminium [34; 35] and stainless steel [36; 37] parts exist in the literature and have highlighted the advantages of the hybrid AM/casting strategy in the manufacture of metallic elements. More recently, the application of artificial intelligence [38] and decision-making metrics [39] in the mould-manufacturing process has permitted addressing sustainability aspects that could, in the future, challenge traditional mass production technologies [40]. In this paper, we describe the fabrication of a closed vane pump impeller by BJ printing of a sand mould followed by casting. Impellers are rotating parts widely used in pumps around the world and are, in many cases, critical to guaranteeing production cycles in the chemical and many other industries. The impeller was fabricated on stainless steel 316 by reverse engineering of an original part made of the same material. We describe the scanning, drawing, and elaboration of constructive 3D plans, as well as the manufacturing of the sand mould by BJ. The mechanical and metallographic characterization of the manufactured impeller is also presented. More importantly, the produced part was put into operation in a centrifugal pump at a polyol/polyglycol plant belonging to Dow Chemical Iberica SL, in Tarragona, Spain. Process variables related to the pump behaviour, such as the pressure and flow of the final product, were measured continuously for several production cycles and compared with the same variables obtained in previous cycles with the original impeller.