Design and Thermal Comparison of Random Structures Realized by Indirect Additive Manufacturing

Abstract

Additive manufacturing (AM) processes are used to fabricate three-dimensional complex geometries. There are several technologies that use laser or electron beam over metal powder beds. However, the direct AM processes have inconveniences such as specific set of materials, high thermal stress traced, high local energy absorbed, poor surface finish, anisotropic properties, high cost of material powder, and manufacturing with high-power beams. In this paper, an alternative process was developed. An indirect additive manufacturing (I-AM) combining a 3D print of castable resin and metal casting in order to obtain a cellular structure similar in shape to commercial metal foams but completely definable as design features was developed. Design of the cellular structure was made by the graphical algorithm editor Grasshopper®. Designed structures were realized by a lost-wax casting process and compared with commercial foam specimens by a system designed for this work. The designed metal foams showed a performance superior to that of commercial metal foam; in particular, the heat thermal coefficient of designed metal foams in the better case was 870 W/m2·K, almost doubled in comparison with the commercial foam tested in this work.

Design and Mechanical Characterization of Voronoi Structures Manufactured by Indirect Additive Manufacturing

“…The foam structure was realized using a method developed in a previous work [23]. The value that defines the distribution of porosities within a metal matrix is defined as pores per inch (PPI).…”

“…Materials 2018, 11, x FOR PEER REVIEW 3 of 12 Figure 1. Process to achieve random structure in a space region by Voronoi tessellation [23].…”

“…However, expensive machineries, as well as low surface finishing and demanding process settings, limit the application of these methodologies in industrial environments [7]. Metal foams are composed of biphasic and cellular materials, which combine good mechanical resistance with excellent thermal and acoustic properties [8].In particular, high specific strength [9][10][11][12][13] and strain [14][15][16], excellent energy absorption [17,18], acoustic insulation [19], and heat dissipation media [20][21][22][23][24] make this class of materials increasingly useful for several multifunctional applications. The main problem afflicting metal foams regards the manufacturing process, and specifically the porosity distribution [25,26], as well as the connection with other components.…”

Evaluation of the effects of the metal foams geometrical features on thermal and fluid-dynamical behavior in forced convection

“…The samples produced were characterized by different PPI values and branches thickness (r) as showed in Table 1; also, two different kinds of edges (smooth/regular) were considered. The structure of the samples was designed with the ad hoc method described in references [41,42]. A Spatial Voronoi Tessellation with the Rhinoceros plug-in GrassHopper was used to design the structure.…”

“…Almonti et al produced a foam structure made of a foundry resin using a 3D stereolithography laser printer. Following, this model was reproduced with a casting process to achieve a metal foam with the designed structure [41,42].…”