This work introduced additively manufactured non-assembly, miniaturized pin-joints for pantographic metamaterials as perfect pivots. The titanium alloy Ti6Al4V was utilized with laser powder bed fusion technology. The pin-joints were produced using optimized process parameters required for manufacturing miniaturized joints, and they were printed at a particular angle to the build platform. Additionally, this process optimization will eliminate the requirement to geometrically compensate the computer-aided design model, allowing for even further miniaturization. In this work, pin-joint lattice structures known as pantographic metamaterials were taken into consideration. The mechanical behavior of the metamaterial was characterized by bias extension tests and cyclic fatigue experiments, showing superior levels of performance (no sign of fatigue for 100 cycles of an elongation of approximately 20%) in comparison to classic pantographic metamaterials made with rigid pivots. The individual pin-joints, with a pin diameter of 350 to 670 µm, were analyzed using computed tomography scans, indicating that the mechanism of the rotational joint functions well even though the clearance of 115 to 132 µm between the moving parts is comparable to the nominal spatial resolution of the printing process. Our findings emphasize new possibilities to develop novel mechanical metamaterials with actual moving joints on a small scale. The results will also support stiffness-optimized metamaterials with variable-resistance torque for non-assembly pin-joints in the future.

The Design for Additive Manufacturing of final products needs to target many design objectives, e.g., function, low lead-time, costs, ecological footprint and possibly more. In balancing the latter, results of design changes are frequently counterintuitive, and this happens especially when it comes to sustainability-related qualities. The latter are commonly modeled by a Life-Cycle Assessment (LCA) of the fabrication and use-phase. However, it is likely that related data is not yet available before most design decisions have been fixed. Even though Additive Manufacturing can enable more design freedom than conventional technologies, the process-specific parameters need strong consideration. The earlier this happens in the design process, improvements might have the biggest impact. Topology optimization can be an efficient method for conceptual design and design automation. However, the respective models often need to be simplified, e.g., regarding nonlinear material properties or intricate manufacturing constraints. For this reason, it is typically not possible in topology optimization to deal with all previously mentioned criteria. A Sustainability-oriented Topology Optimization method is proposed within a generative engineering framework. Multimodal analyses of intermediate topology results should enable the computation of intricate measures. For example, regarding Laser Powder Bed Fusion-based Additive Manufacturing expedient build directions and an estimation of support structures are calculated. A predictive LCA model is included that calculates the ecological footprint measures on basis of the intermediate topology results. For that purpose, a simplified product system with representative processes is modeled. The presented approach enables a more holistic Design for Additive Manufacturing that can deal with a multitude of multidisciplinary criteria in a coherent way. Keywords Generative Engineering Topology Optimization Sustainability Sustainable Design Lightweight Design Metal Additive Manufacturing Design Automation Life-Cycle Assessment Design for Additive Manufacturing

This work presents an approach to introduce significant strain rate sensitivity into metallic metamaterials that are manufactured via additive manufacturing, where the base material employed will typically have a weak strain rate sensitivity. Here, we employ friction between the rough surfaces as the strain-rate dependent mechanism, whose magnitude is tunable by optimizing the geometry. The design along with the preliminary simulation results of the friction unit cell is presented. This work will quantify the effects of geometrical parameters on the dissipated energy.