Christian Bay

The surge in global population growth and the escalating demand for social and economic prosperity present formidable challenges in the 21st century. However, asserting the sustainability of some ecological impact reduction initiatives, such as recycling, requires a comprehensive evaluation within various domains, including performance, ecology, and economics, and contemporary advancements in integrating quantitative assessments of material and manufacturing properties, coupled with mathematical decision-making approaches, contribute to mitigating subjectivity in determining the efficiency of recycling. This paper implements a robust multi-criteria decision-making (MCDM) approach to address the complexities of recycling, validating its implementation and effectiveness through a case study. The focus is set on the application of bio-based polylactic acid (PLA) and petroleum-based polypropylene (PP) additively manufactured (AM) parts produced through Fused Filament Fabrication (an approach to ecology/performance domains). The work introduces a cost analysis focusing on calculating thermomechanical recycling within the economic domain. The well-known Analytical Hierarchical Process (AHP) provides a structured framework for decision-making (the ecological impact domain) with the focus being on application. The assessment or recycling viability, encompassing AHP calculations, preprocessing, and supplementary tools, is provided by developing an open-source software tool for practitioners in the field of material science and manufacturing. The results indicate a preference for industrial-scaled recycling over virgin or lab-recycled manufacturing, particularly for petroleum-based polypropylene. The versatility and simple utilization of the software tool allow seamless integration for diverse use cases involving different materials and processes.

Polymers have a reputation for several advantageous characteristics like chemical resistance, weight reduction, and simple form-giving processes. The rise of additive manufacturing technologies such as Fused Filament Fabrication (FFF) has introduced an even more versatile production process that supported new product design and material concepts. This led to new investigations and innovations driven by the individualization of customized products. The other side of the coin contains an increasing resource and energy consumption satisfying the growing demand for polymer products. This turns into a magnitude of waste accumulation and increased resource consumption. Therefore, appropriate product and material design, taking into account end-of-life scenarios, is essential to limit or even close the loop of economically driven product systems. In this paper, a comparison of virgin and recycled biodegradable (polylactic acid (PLA)) and petroleum-based (polypropylene (PP) & support) filaments for extrusion-based Additive Manufacturing is presented. For the first time, the thermo-mechanical recycling setup contained a service-life simulation, shredding, and extrusion. Specimens and complex geometries with support materials were manufactured with both, virgin and recycled materials. An empirical assessment was executed through mechanical (ISO 527), rheological (ISO 1133), morphological, and dimensional testing. Furthermore, the surface properties of the PLA and PP printed parts were analyzed. In summary, PP parts and parts from its support structure showed, in consideration of all parameters, suitable recyclability with a marginal parameter variance in comparison to the virgin material. The PLA components showed an acceptable decline in the mechanical values but through thermo-mechanical degradation processes, rheological and dimensional properties of the filament dropped decently. This results in significantly identifiable artifacts of the product optics, based on an increase in surface roughness.

Additive Manufacturing (AM) as much as sustainability aspects gained increasing attention in the last couple of years. The vision of resource-efficient manufacturing at batch size one is often claimed as an outstanding property of AM. Fused Filament Fabrication, as one of the most used AM technologies, satisfies this statement only in a restricted sense, through simple handling for non-experts and low-cost materials and machines. Next to performance-driven and process-influencing attributes, the question of a general ecological improvement through thermo-mechanical recycling rises. Therefore, recycling options of the thermoplastics are mandatory to explore. Based on the ISO 14040/44 Life Cycle Assessment (LCA) methodology two different geometries were environmentally assessed during a primary process cycle, using, and recycling. Each geometry was manufactured by a bio-based polymer and internationally produced (PLA) and petroleum-based locally produced polymer (PP) with a corresponding support filament. The methodological approach demonstrates an option how to evaluate the field of AM and recycling regarding environmental aspects. Furthermore, an adaption of the sensitivity towards industrial parameters (material/energy efficiency) showed an ecological benefit concerning recycling.

In this paper, the influence of the surface roughness of build plates as well as the process parameters laser power, scan speed and exposure curing time on the bonding of additively manufactured components made of TiAl₆V₄ to the build plates is analyzed. These analyses are carried out with build plates made of Titanium Grade 2 and AlMgSi0.5. The analyses show that higher surface roughness leads to lower bending strength and thus poorer bonding of components on the build plate. In addition, it is shown that the bending strength normalized to the bonding surface decreases at high laser power, especially at high scanning speeds. Furthermore, multiple exposure results in lower flexural strength.

Der hohe lokale Energieeintrag beim pulverbettbasierten Schmelzen mittels Laserstrahl (laser powder bed fusion, LPBF) bewirkt hohe Temperaturgradienten. Dies führt zu thermisch induzierten Eigenspannungen und Verzug in den gefertigten Bauteilen, wodurch deren Form- und Maßhaltigkeit negativ beeinträchtigt wird. In diesem Beitrag wird der Einfluss der Bauteilgeometrie und einer der Fertigung nachgelagerten Wärmebehandlung auf den Verzug von mittels LPBF gefertigten Bauteilen aus dem Werkstoff TiAl6V4 untersucht. A high local energy input during laser powder bed fusion (LPBF) creates high temperature gradients. This leads to thermally induced residual stresses and distortion, which negatively affect the dimensional accuracy of components. This paperinvestigates the influence of component geometry and heat treatment after the manufacturing process on the distortion of components made by LPBF of TiAl6V4.