Mechanical Reclamation of Waste Sand Produced by Additive Manufacturing Processes

Abstract

Metal casting manufacturers are increasingly adopting three-dimensional printing in their workflows as a way to remain competitive. Despite all the innovative development, strict environmental regulations and the intrinsic value of sand still make the recycling of waste sand an essential matter to consider when implementing the rapid sand-casting process. During the printing of the furan-bonded sand cores using binder jetting processes, waste sand is produced. This paper investigates the possibility of mechanically reclaiming the waste sand generated during the printing of sand cores. In this study, waste furan-bonded sand that was generated by three-dimensional printing using the Voxeljet VX 1000 printer was collected from the Vaal University of Technology. The collected waste sand was first characterised before being mechanically reclaimed using dry attrition, followed by dry screening and wet attrition, which involved washing the waste sand in a liquid solution of water and isopropyl alcohol. The results showed that mechanical reclamation using wet attrition is more effective in removing the residual binder in the sand than mechanical reclamation using dry attrition.

Thermal reclamation of used sand produced by binder jetting processes

“…A previous study was conducted to characterise the waste sand generated during threedimensional printing (3DP) on a Voxeljet printer, which included properties such as size distribution, grain shape, loss on ignition (LOI), and pH [12]. The pH results confirmed the presence of residual sulphonic acid and furfuryl alcohol resin in the used sand obtained from the 3DP process after printing.…”

“…Figure 11 and Figure 12 for all three sands reclamation were over the minimum requirement of 200 N/cm 2 therefore all three reclamation methods can be considered effective. According to the study conducted by Motlhabane et al (2022) [18] results showed that mechanical reclamation by dry attrition the tensile strength could achieve the minimum requirement of 220 N/cm 2 . Used sand 2 was above the minimum tensile strength requirement for all the reclamation methods.…”

Effects of used sand recycling on the foundry properties of three-dimensional printed sand moulds and cores

“…The binder jet printing is best explained by Figure 1 below. [4] After printing the sand moulds and cores, any loose sand is carefully removed and disposed of or could be recycled and reclaimed [5]. The reclamation processes are normally mechanical and thermal reclamation.…”

“…The degree to which the sand has been heated directly correlates with the efficiency of the sand reclamation process and up to 90% of reclaimed sand may be used. Motlhabane et al [5] have studied the mechanical reclamation of the wasted sand generated by the 3D Printing. It was found that it could produce renewed sand complying with the specification of the Original Equipment Manufacturer, which is the Voxeljet VX1000.…”

“…On the other hand, thermal reclamation involves heating the waste sand to about 800 o C in the oxidizing atmosphere in order to burn off the binder present on the sand particles. This method is capable of reclaiming 100% of the bonded sand [5][6] [7]. However, during three-dimensional printing, the sand particles barely come in contact with the binder.…”