2023 Annual International Solid Freeform Fabrication Symposium (SFF Symp 2023): Applications: Lattices and Cellular I
Program Organizers: Joseph Beaman, University of Texas at Austin
Monday 1:30 PM
August 14, 2023
Room: Salon B
Location: Hilton Austin
Session Chair: Denis Cormier, Rochester Institute of Technology
1:30 PM
Directional Dependence of IN718 Gyroid TPMS Lattices Fabricated by Selective Laser Melting: Bharath Ravichander1; Shweta Hanmant Jagdale1; Golden Kumar1; 1University of Texas at Dallas
Inconel 718, a nickel-based superalloy that has impressive mechanical properties such as tensile and impact resistance, as well as resistance to corrosion at high temperatures. One commonly used cellular structure is the gyroid lattice, which is a type of triply periodic minimal surface that can be customized to create lightweight materials with adequate strength and low stiffness. Selective laser melting (SLM) process has made it possible to manufacture these complex structures, and the properties can be controlled by adjusting various process parameters such as scan strategy, laser power, and build direction. However, the impact of build orientation on the properties of the lattices has not been extensively studied. This work focused on fabricating gyroid lattice structures at different build orientations, and the microstructural and mechanical properties of the structures were studied through Scanning electron microscopy and quasi-static compression tests.
1:50 PM
Towards the Limits in Copper Lattice Production via Fiber Laser Powder Bed Fusion: Michel Smet1; Louca Goossens1; Sam Buls1; Brecht Van Hooreweder1; 1KUleuven
Laser Powder Bed Fusion of copper paves the way for innovation in thermal systems and heat transfer devices. Recent simulations have shown that by interchanging typical fin designs with more complex structures an overall improvement in pressure drop and weight can be obtained while offering the same thermal performance. Small-scale lattice structures are especially of interest for AM as they form a reliable, periodic infill. However, until now, their study has been mainly theoretical. To analyse these structures, an in-house built LPBF machine at KU Leuven has been successfully used to manufacture pure copper parts. Measurements showed a conductivity exceeding 100%IACS, which is the result of low contamination and low porosity in the as-built material. In this work, the parameter optimisation for thin-walled lattices is discussed in combination with an in-depth review of the thermal properties of the resulting structures.
2:10 PM
Additive Manufacturing of Hybrid Sandwich Sheets by Laser Powder Bed Fusion of Metals: Sebastian Platt1; Norman Schnell1; Gerd Witt1; Stefan Kleszczynski1; 1Universität Duisburg-Essen
Within lightweight applications, powder bed fusion of metals using a laser beam (PBF-LB/M) allows the realization of filigree structures at minimal use of material. A traditional element of lightweight construction are sandwich sheets. These lightweight elements contain both geometrically simple (cover sheets) and geometrically complex (core structure) elements. Conventional Manufacturing of core structures is limited in terms of complexity. Additive Manufacturing of sheets has disadvantages in terms of economic efficiency. A combination of additive and conventional manufacturing processes is proposed to eliminate both disadvantages. Therefore, this publication presents a fabrication route to produce hybrid sandwich sheets. The hybrid sandwich sheets are manufactured using a rolled cover sheet (<1 mm) as base plate and additive manufactured core structures including an upper cover sheet. A developed mounting system for implementation in the PBF-LB/M process is presented and evaluated concerning manufacturing criteria such as process stability and dimensional accuracy of the built-up components.
2:30 PM
Fabrication of Supportless Lattice Structures Using Burst Mode Drop-on-Demand Liquid Metal Jetting: Paarth Mehta1; Usama Rifat1; Denis Cormier1; 1Rochester Institute of Technology
The properties of topology optimized metallic additively manufactured (AM) lattice structures have been extensively studied to date. One challenge with using powder bed or vat AM processes, however, is that lattice structures that are enclosed by solid skin surfaces cannot be produced, as it would be impossible to remove trapped powder or liquid. This talk will present advances in support-free fabrication of engineered lattice structures using drop-on-demand liquid metal jetting (LMJ). This approach enables fabrication of completely enclosed lightweight lattice structures. A burst-mode jetting strategy is introduced in which multiple droplets are ejected at high frequency followed by a brief delay to allow the droplet cluster to partially solidify. By varying the drops/burst, frequency, stepover distance, and pause time, struts can be produced with a range of diameters and inclination angles without supports. Experimental results, including characterization of density, microstructure, and mechanical properties will be presented.
2:50 PM
Towards Experimental Process Parameter Development for Ti-6Al-4V TPMS Lattice Structures with Application to Small Scale Dental Implants using Micrographs: Anne Jahn1; Hui Li1; Nicole Emminghaus1; Tatjana Melnyk1; Jörg Hermsdorf1; Stefan Kaierle1; 1Laser Zentrum Hannover e.V.
Ti-6Al-4V is a widely used alloy in implant engineering and lattice structures are applied to locally align the stiffness of the implant to the one of bone. Triply periodic minimal surface (TPMS) structures are popular due to their curved surface and good manufacturability. Tests with different TPMS structures showed a strong interaction between design factors and manufacturing parameters resulting in the need for individual parameter development. However, to the best of our knowledge, the most work in the current literature focusses on mechanical and biological examinations of TPMS structures manufactured with standard parameters. As process parameters influence the structural properties, the optimum values for further analysis may not have been investigated (e.g., their influence on microstructure and mechanical properties). In this work, a design of experiments approach is used to develop process parameters. As computer tomography scans are resource intensive for large scale parameter development, a sparser approach using micrographs for porosity analysis is introduced. Small structures with unit cell size as small as 1.0 mm are fabricated on an industrial machine. Our initial studies show that the design factor pore size is negligible in comparison to wall thickness when optimizing internal porosity.
3:10 PM Break
3:40 PM
Bio-inspired AM Structure using Co-extruded Continuous Carbon Fibre Reinforcement: Piyapat Jameekornkul1; Ajit Panesar1; 1Imperial College London
The bio-inspired cellular structure has been recognised as an innovative approach in Additive Manufacturing (AM) for lightweight and energy absorption applications. In this study, the objective is to investigate the use of continuous carbon fibre AM (C-FRAM) co-extrusion technology to manufacture the lattice structures inspired by the helicoidal structure and Kersling folding mechanism. The corresponding mechanical properties of the bio-inspired reinforced honeycomb and squared-grid 2D structure will be reported under quasi-static compression test. The interlayer pitch angle of reinforced path will be varied from 0 to 90° which the adhesive area will be observed. The Kersling pattern is introduced to further the understanding of the continuity of reinforcement stacking. This work aims to demonstrate the applicability of C-FRAM to enhance the potential design for high-strength and light-weighting infills.
4:00 PM
Development of Artificially Tuned Microstructure using Interpenetrating Lattices Fabricated by Laser Powder Bed Fusion: Shweta Hanmant Jagdale1; Bharath Ravichander1; Golden Kumar1; 1University of Texas at Dallas
The continuous demand of better performance of product has led designers to design parts innovatively. Laser powder bed fusion (LPBF), a well-adapted additive manufacturing processes which fabricates near net shaped fully dense complex metal parts with accuracy. Quality of the printed parts depends on the laser process parameters such as, laser power, hatch distance, scan speed, scan strategy and layer thickness. Mechanical properties have strong dependence on the laser process parameters and direction of the build. LPBF part exhibits anisotropic microstructure and mechanical properties. In this work, LPBF is used to fabricate interpenetrating lattices with enhanced mechanical and functional properties than the non-reinforced metallic alloys by using innovative interpenetrating TPMS lattices. Interpenetrating lattices are fabricated with LPBF process by selecting two different sets of laser process parameters which shows different microstructural and mechanical properties. Relative density analysis, micrographic analysis and Vickers microhardness analysis is carried out in the printed composites.
4:20 PM
Additively Manufactured Molds for Large Gyroid Structures Cast from Concrete: Joseph Bartolai1; Simon Miller1; Michael Yukish1; 1Pennsylvania State University
This work presents the design of additively manufactured molds use to cast large gyroid patterns from concrete. Key contributions are the method of segmentation of the continuous gyroid structure into castable subsections that tile the space in 3D via “rods” with hexagonal symmetry, and the design of the separable multi-section molds that accommodate the gyroid’s complex geometry. These mold sections are additively manufactured using Thermoplastic Polyurethane (TPU) so that when combined they form all of the complex features of the gyroid shape. Upwards of 60 segments make up the more complex molds, with the TPU’s flexibility critical to mold release. The TPU has proven surprisingly robust, with over 60 casts from the same sections. The paper presents the design history for the molds, the current final design, and recommendations for expanding to other Equation-Based Lattice shapes.