Lightweight Metal Cellular Structures Fabricated via 3D Printing of Sand Cast Molds

Abstract

Cellular structures offer high specific strength and can offer high specific stiffness, good impact absorption, and thermal and acoustic insulation. A major challenge in fabricating cellular structures is joining various components. It is well known that joints, either welded or bolted or bonded with an adhesive, serve as stress concentrators. Here, we overcome this shortcoming by the use of metal casting into 3D printed sand molds for fabricating cellular structures and sandwich panels. Furthermore, the use of 3D printing allows for the fabrication of sand molds without the need for a pattern, and thus enables the creation of cellular structures with designed mesostructure from a bevy of metal alloys. We use the finite element method to numerically analyze the energy absorption capabilities of an octet truss cellular structure created with the proposed manufacturing process and that of a solid block of the same material and area density as the cellular structure. In the numerical simulations, mechanical properties collected through experimental quasi-static compression testing are employed. It is found that indeed the cellular structure absorbs considerably more impact energy over that absorbed by a solid structure of the same weight.

Investigation of process parameter effect on anisotropic properties of 3D printed sand molds

“…A minimum nominal strength is required for an easy manipulation of the mold and good dimensional accuracy of the casting. This rigidity should be obtained with a minimum 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 binder resolution (XR = 140 µm), that means small Loss-On-Ignition values, to reduce the off-gassing that hinders the filling of the sand mold cavity [5,13,14,29].…”

“…Among the various existing binders, foundries commonly use the organic furan binder in 3D printing machines for the mold manufacturing to cast light alloys [5,11,14,16,17,31]. A 3D printer manufactures molds by successive layers of deposited sand with the addition of a controlled amount of resin at the future mold positions.…”

“…While some studies investigated the process parameter effects on mold properties [12,26] [11], only one [11] quantified the heterogeneous properties of sand molds within the same job-box. Moreover, few published on the properties of furan sand molds printed by ExOne 3D printer [5,14].…”

The role and impact of 3D printing technologies in casting

“…And, the voids provide cooling channels in the sand mould. 3D printing can be used to cast complicated structures, not just regular castings, for example, a mesostructure (a lattice truss structure) [76] . However, the current CAD tools are limited by the feature-based solid model construction method.…”

3D Printed Smart Molds for Sand Casting

“…More generally, substantial research has been focused on 3D printed sand molds including the material systems (e.g., binders and silica), 7,18,21 properties such as surface finish and porosity, 2,15,22 complex multi-material structures, 16,17 modeling of the process 12 and even sensing in smart sand molds 8 in which temperature sensors were inserted into 3D printed sand molds, and the survival and utility of the sensors were evaluated. An entire community has researched ink jetting, the foundational process of binder jetting, and the process is well understood and modeled.…”