The Design of 3D-Printed Lattice-Reinforced Thickness-Varying Shell Molds for Castings

Abstract

3D printing technologies have been used gradually for the fabrication of sand molds and cores for castings, even though these molds and cores are dense structures. In this paper, a generation method for lattice-reinforced thickness-varying shell molds is proposed and presented. The first step is the discretization of the STL (Stereo Lithography) model of a casting into finite difference meshes. After this, a shell is formed by surrounding the casting with varying thickness, which is roughly proportional to the surface temperature distribution of the casting that is acquired by virtually cooling it in the environment. A regular lattice is subsequently constructed to support the shell. The outside surface of the shell and lattice in the cubic mesh format is then converted to STL format to serve as the external surface of the new shell mold. The internal surface of the new mold is the casting’s surface with the normals of all of the triangles in STL format reversed. Experimental verification was performed on an Al alloy wheel hub casting. Its lattice-reinforced thickness-varying shell mold was generated by the proposed method and fabricated by the binder jetting 3D printing. The poured wheel hub casting was sound and of good surface smoothness. The cooling rate of the wheel hub casting was greatly increased due to the shell mold structure. This lattice-reinforced thickness-varying shell mold generation method is of great significance for mold design for castings to achieve cooling control.

Mechanical Analysis of Ceramic/Polymer Composite with Mesh-Type Lightweight Design Using Binder-Jet 3D Printing

“…In a study by Shangguan et al [ 18 ], they fabricated molds with a shell-truss structure using 3D printing, reducing the use of materials by two-thirds compared to conventionally-made molds. In addition, the cooling time of melting aluminum could be successfully controlled by the application of lightweight structures [ 19 ]. Deng et al [ 20 ].…”

Modeling and Simulation of the Casting Process with Skeletal Sand Mold

“…The mechanical behavior of the skeletal sand mold is very important in the thermomechanical coupled modeling and simulation. Its strength, measured by Shangguan et al [21], declines significantly with temperature, as shown in Figure 3. Usually, the sand mold is neglected or treated as an elastic model.…”

Casting of complex structures in aluminum using gypsum molds produced via binder jetting

“…The available research studies have been focused on the influence of the following process parameters (Hodder and Chalaturnyk, 2019): analysis of the cast dimensional accuracy pouring aluminum alloys (Le Néel et al , 2018b); measuring the influence of the part/wall thickness on the part cooling time (Walker et al , 2018); leverages binder jetting technology to design a smart molds with sensor integrated to study the thermodynamics and physics of the casting process (Szymański and Borowiak, 2019); testing the effect of different sand graininess and different binder on the casted part roughness. Furthermore, several studies have been conducted on the generation of complex molds via the use of 3D printing: cellular structures have been designed to obtain complex aluminum (Snelling et al , 2015; Kim et al , 2018) and iron casts (Wang et al , 2019; Druschitz et al , 2017) or lattice-reinforced thickness-varying shell molds (Shangguan et al , 2018; Shangguan et al , 2017).…”