Effect of hollow core on cooling temperature in 3D printing

3D printing is a very promising method for sand mold manufacturing with a shorter design time and simpler manufacturing process compared with conventional technology in the casting industry. The heat preservation and feeding effect of the riser can effectively reduce the occurrence of shrinkage cavity and porosity in the casting. Therefore, the insulation effect of the riser is an important index to evaluate sand mold design. In this study, a hollow sand core was designed and used for casting a cylindrical thin-walled part by the binder jetting 3D printing method. The temperature change curve of the hollow core during the No. 35 steel pouring process and the riser site during the A356 aluminum alloy solidification process in this sand mold was tested to explore the effect of the hollow core on the cooling process. The A356 pouring results showed that the concretion time of the riser with a hollow core was prolonged by over 20%; the cooling rate of casting was accelerated by over 20% by applying this hollow core before sand shakeout. The No. 35 steel pouring facts reflected that the temperature rise rate of the solid core was more visible than that of the hollow core in the early process of casting solidification. The work in this paper indicated that a sand core with a hollow structure could not only accelerate casting cooling but also draw out the concretion duration of the riser to improve its supplying function and can reduce the thermal expansion of the sand core. This study provides a new and effective design idea for 3D printed sand core, which can be used as a reference for the design of 3D sand core molds and the research of casting solidification and cooling.