Achieving Triply Periodic Minimal Surface Thin-Walled Structures by Micro Laser Powder Bed Fusion Process.

Junhao Ding,Shuo Qu,Xu Song

doi:10.3390/mi12060705

Junhao Ding, Shuo Qu + Show 1 more

Open Access

https://doi.org/10.3390/mi12060705

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Journal: Micromachines	Publication Date: Jun 16, 2021
Citations: 20	License type: CC BY 4.0

Affiliation: Chinese University of Hong Kong

Abstract

Recently, triply periodic minimal surface (TPMS) lattice structures have been increasingly employed in many applications, such as lightweighting and heat transfer, and they are enabled by the maturation of additive manufacturing technology, i.e., laser powder bed fusion (LPBF). When the shell-based TPMS structure’s thickness decreases, higher porosity and a larger surface-to-volume ratio can be achieved, which results in an improvement in the properties of the lattice structures. Micro LPBF, which combines finer laser beam, smaller powder, and thinner powder layer, is employed in this work to fabricate the thin-walled structures (TWS) of TPMS lattice by stainless steel 316 L (SS316L). Utilizing this system, the optimal parameters for printing TPMS-TWS are explored in terms of densification, smoothness, limitation of thickness, and dimensional accuracy. Cube samples with 99.7% relative density and a roughness value of 2.1 μm are printed by using the energy density of 100 J/mm3. Moreover, a thin (100 μm thickness) wall structure can be fabricated through optimizing parameters. Finally, the TWS samples with various TPMS structures are manufactured to compare their heat dissipation capability. As a result, TWS sample of TPMS lattice exhibits a larger temperature gradient in the vertical direction compared to the benchmark sample. The steady-state temperature of the sample base presents a 7 K decrease via introducing TWS.

Highlights

Cellular structures have shown attractive multifunctionalities due to the complicated geometries and scale effect [1]
thin-walled structure (TWS) sample of triply periodic minimal surface (TPMS) lattice exhibits a larger temperature gradient in the vertical direction compared to the benchmark sample
The emergence of additive manufacturing (AM), or commonly known as 3D printing, is proven to be a feasible approach to fabricate complex models like TPMS [3], which accelerates the research on thin-walled TPMS applications

Summary

Introduction

Cellular structures have shown attractive multifunctionalities due to the complicated geometries and scale effect [1]. As a group of mathematically defined cellular structures, the triply periodic minimal surface (TPMS) lattice structure has fascinating properties which possess smooth surfaces without sharp corners or joints and a large surface area to volume ratio. It has been demonstrated that TPMS architecture holds great potential in revolutionizing many engineering applications such as tissue engineering, catalytic substrates, and heat exchangers [2]. The fine features and sophisticated surfaces of TPMS pose a great challenge to conventional manufacturing techniques. In terms of convective heat transfer, the heat dissipation of TPMS structure is typically proportional to the surface area, meaning that thinner walls are more beneficial under convection [6]. As to the heat exchangers applications, the TPMS structure necessitates a leak-free design, and thin walls minimize resistive-thermal losses [7]. Gradient thickness [8] and cell size [9] have been

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