Process capability investigation on the 3D printing technique for hybrid silica-based sands cores

Sand Binder Jetting is one of the most important innovations that foundry field experienced in recent years. One of the main challenges of Binder Jetting consists in the handling of the large machine volumes and in the consequent tendency to show building box inhomogeneity, in terms of performance and quality of the printed pieces. This paper presents a process capability study of an industrial sand printer, used in the field of cores for the cast iron foundry of hydraulic valves, with a focus on the part dimensional accuracy and mechanical resistance (bending strength). Printing orientation of the parts, as well as their positioning inside the building box, are considered as factors of the investigations. Results show that the printing direction is the most impactful parameters, whereas the Z oriented parts show less dimensional accuracy and the weakest mechanical resistance. XY location in the layer is also seen to vary the parts resistance, more than the parts accuracy. Part density varies by about 20% while their bending resistance of about 30% in the building box. Expressions of an existing correlation between parts resistance and part density are observed, but these are not strong enough to justify all of the observed results.