Novel post-processing procedure to enhance casting molds manufactured by binder jetting AM

Abstract

The significant improvements made in additive manufacturing (AM) techniques since their beginnings, coupled with its intrinsic advantages, have resulted in a technology that stands out as most suitable for applications in leading sectors today. In addition to some of the properties of the parts, there are also some inherent aspects of AM techniques that hinder their applicability. In this respect, the application of calcium sulfate parts manufactured by binder jetting (BJ), as expendable casting elements, is limited by both the high quantity of volatile substances, due to the BJ process, and their low compression resistance. In this work, a novel part post-processing procedure is presented. This procedure consists of applying various heat treatments, in combination with a vacuum infiltration process using an Epsom salt solution. The procedure reduces the volatile content of BJ AM parts and enhances the compression strength with little modification to the part geometry. This post-processing substantially improves the applicability of BJ AM parts as expendable casting elements. After presenting this novel procedure and analyzing the significant enhancement of the properties of the AM calcium sulfate parts (i.e. permeability, the reduction of volatile content and reduction of compressive strength), a case study is presented with an expendable mold for aluminum casting. This procedure allows for a safer casting process, improves the part’s surface quality and reduces the internal porosity of the cast parts.