Analysis and Design of Lattice Structures for Rapid-Investment Casting

Abstract

This paper aims to design lattice structures for rapid-investment casting (RIC), and the goal of the design methodology is to minimize casting defects that are related to the lattice topology. RIC can take full advantage of the unprecedented design freedom provided by AM. Since design for RIC has multiple objectives, we limit our study to lattice structures that already have good printability, i.e., self-supported and open-celled, and improve their castability. To find the relationship between topological features and casting performance, various lattice topologies underwent mold flow simulation, finite element analysis, casting experiments, and grain structure analysis. From the results, the features established to affect casting performance in descending order of importance are relative strut size, joint number, joint valence, and strut angle distribution. The features deemed to have the most significant effect on tensile and shear mechanical performance are strut angle distribution, joint number, and joint valence. The practical application of these findings is the ability to optimize the lattice topology with the end goal of manufacturing complex lattice structures using RIC. These lattice structures can be used to create lightweight components with optimized functionality for various applications such as aerospace and medical.

Aluminum Auxetic Structures Produced Using Combined Stereolithography and Investment Casting

“…For the solid mold IC variation, a key factor to consider is the temperature the mold is kept at during pouring. This value varies between metals and Richard et al [26] mentions that for brass and aluminum alloys, the mold temperatures should be approximately 538°C and 315°C respectively. For stainless steel alloys, Bansode et al [27] held their mold temperature between 1050°C and 1100°C prior to pouring.…”

“…When solid mold IC is paired with rapid investment casting (RIC) -which is a process that benefits from AM as the wax pattern can be 3D printed -intricate lattices have been created. Through RIC, the costly process of injection molding of the initial wax pattern is substituted with a means of 3D printing to produce the pattern in a more cost effective way [26]. Richard et al [26] used a rapid solid mold investment casting process to produce a rhombic, kelvin cell, cubic and octet-truss lattice structures from both brass and aluminum.…”

“…Through RIC, the costly process of injection molding of the initial wax pattern is substituted with a means of 3D printing to produce the pattern in a more cost effective way [26]. Richard et al [26] used a rapid solid mold investment casting process to produce a rhombic, kelvin cell, cubic and octet-truss lattice structures from both brass and aluminum. The motive was simply to attempt to produce structures of high complexity using an RIC process in light of future applications in the aerospace and medical field [26].…”

Experimental investigation of mechanical properties and energy absorption capabilities of hybrid lattice structures manufactured using Fused Filament Fabrication

“…Despite the numerous advantages and applications of lattice structures, their manufacturing using conventional methods is complicated due to the intricate geometry of the parts. In one of the recent studies, it was found that vacuum-assisted rapid investment leads to multiple defects such as incomplete filling and premature solidification of several lattice topologies [14]. As a result, additive manufacturing (AM) remains the main method to produce lattice structures.…”

Microstructure and Properties of Hollow Octet Nickel Lattice Materials

“…Finally, the internal polymer skeleton is removed by sintering or chemical etching to obtain a metal or ceramic hollow lattice [ 12 , 13 , 14 , 15 ]. Compared with investment casting, wire weaving and selection laser melting (SLM) and electron beam melting (EBM), hollow lattices prepared by polymer backbone and plating process have the advantages of high precision, ultralight, thin wall thickness and high specific surface area [ 16 , 17 , 18 , 19 , 20 ]. Schaedler et al used self-propagating photopolymer waveguides (SPPW) and electroless plating processes to prepare a hollow octahedral NiP lattice with a wall thickness of 120 nm and a density of 0.9 mg/cm 3 .…”