###### Abstract  
The emergence of additive manufacturing is renovating the landscape of available production technologies. In this paper, we describe the fabrication of a closed vane pump impeller (\(\Phi\) 206 mm, height 68 mm, weight 4 kg) by binder jetting 3D printing of a sand mould followed by casting using stainless steel 316 to create an identical copy of a part in service in a chemical plant in Tarragona, Spain. The original part was reverse engineered and used to create a sand mould by binder jetting 3D printing on which new impellers were fabricated by casting. Metallographic studies showed an austenitic matrix with 6.3% of erritic phase and 40 \(\upmu\)m \(\times\) 8 \(\upmu\) ferrite grains without precipitated carbides. The impeller was put into operation in a centrifugal pump at a polyol/polyglycol plant belonging to Dow Chemical Iberica SL from October 2020 to April 2021. Process variables related to the pump behaviour were compared with the same variables obtained in previous cycles with the original impeller for three different product viscosities (30, 180, and 500 cSt). At 500 cSt, the average current consumption was 9.34 A as compared with the 9.41 A measured with the original impeller. Similarly, the pump pressure remained essentially constant during process operation with both impellers (3.97 bar with the new impeller vs. 3.99 bar with the old). Other monitored parameters (product flow, tank level) were similar in both cases, validating the fabrication strategy from an operational point of view. This work further demonstrated that the implementation of additive manufacturing technologies in chemical process engineering is a useful solution to fabricate spare parts that are difficult to replicate with other technologies, providing consequent economic benefits. additive manufacturing; 3D printing; binder jetting; sand mould; impeller +
Footnote †: journal: Applied Sciences  
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Fabrication of a Stainless-Steel Pump Impeller by Integrated 3D Sand Printing and Casting Mechanical Planting and Cast  
Chemical engineering has also recently benefitted from the emergence of AM technologies, which are expected to transform process and reaction engineering and impact many chemical industries [5; 6; 7]. Advantages of their application include energy saving, increased reaction [8] and separation efficiency [9], novel (photo)catalysts [10], etc., and further development can be expected in the future. Several examples of microfluidic devices [11], mixers [12], and reactors [13], among many others, can be found in the literature [5; 6]. Most of these printed devices have been made on polymeric materials such as fluorinated polyethers [14], but glass [15], ceramics [16], and, more recently, metallic precursors [17] have also been employed. While 3D printing is mostly amenable for prototyping and small-scale production of relatively small devices, large metallic components such as pump impellers are still challenging. Metallic parts can be 3D printed using powders or wires of a wide range of metals as starting materials by beam-based (mostly laser-based) or beamless techniques [18; 19]. Metal AM technologies enable the production of complex structures [20; 21] with low residual stress, avoid oxidation, and allow control over the microstructure of the final product but have some disadvantages, such as high costs and energy consumption, the need for expensive manufacturing machines, and, in many cases, the need for postfabrication processing steps to generate the finished part [22]. For this reason, hybrid manufacturing processes combining AM mould printing with metal casting constitute an alternative that increases design flexibility and reduces production times over traditional casting on sand moulds [23]. Binder jetting (BJ) 3D printing is the most popular technology for producing sand moulds for casting [24]. In BJ, a thin layer of powder particles (metal, acrylic, or sandstone) is first deposited on the building deck.