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.

In 2021, sales of electric bicycles in Germany increased compared to the previous year, leading to a 43% share of electric bicycles in the total German bicycle market. The German Bicycle Industry Association (ZIV) expects this growth to continue and that by 2025 every second bicycle sold in Germany will have an electric motor. Therefore, due to the increasing number of sales, both the built-in resources and the possible treatments after the use phase need to be considered regarding sustainable market development. In this context, remanufacturing is one promising end-of-life strategy that enables a new life cycle of products and components, thus reducing the consumption of natural resources and minimizing waste production. The used products are restored to their original conditions by disassembling, cleaning, sorting, reworking, and reassembling. Disassembly is a decisive process step as it creates the prerequisites for all further steps in the process chain and significantly determines the economic feasibility of a remanufacturing process. Therefore, this paper aims to evaluate the ease of disassembly of electric bicycle motors and thus determine their suitability for remanufacturing. To evaluate the disassemblability, the ease of Disassembly Metric (eDiM), a quantitative assessment method for evaluating disassembly effort, was adapted to the needs of the electric bicycle motors. The method was finally applied to five electric bicycle motors from established manufacturers and assessed their ease of disassembly. The results show that the electric bicycle motors can be disassembled without significant damage and classified as suitable for remanufacturing.

Remanufacturing is one key element of a circular economy by closing the loop on the product level and thus maintaining or restoring the product design and the associated product properties. The remanufacturing process chain involves disassembly of used products, cleaning of parts, inspection and sorting of parts, reconditioning or replenishment by new parts, and product reassembly into as-new products. If new parts are required, additive manufacturing is a promising alternative to conventional manufacturing or the purchase of spare parts. Additive manufacturing is characterized by the layered or element-based construction of parts and does not require product-specific tools, enabling a cost-efficient production of individual pieces or small series. The use of specific design rules in product and process development to meet the requirements of the intended process enables and simplifies additive manufacturing or remanufacturing. Despite the design rules for additive manufacturing and remanufacturing, there are no design rules for implementing additive manufacturing technology in the remanufacturing process. In this paper, existing design rules on Design for Additive Manufacturing and Design for Remanufacturing will first be identified and compared, and possible synergies and conflicts of objectives will be analyzed. Based on this, a guideline for a Design for Additive Remanufacturing is developed to facilitate and promote the implementation of additive manufacturing in remanufacturing. The developed design rules enable the evaluation of a part aimed to be produced by additive manufacturing within the remanufacturing process and give advice on how to optimize the design of the part. This paper aims to derive general design rules for a “Design for Additive Remanufacturing” that specifically address the additive remanufacturing process.

Lithium-ion batteries are major drivers to decarbonize road traffic and electric power systems. With the rising number of electric vehicles comes an increasing number of lithium-ion batteries reaching their end of use. After their usage, several strategies, e.g., reuse, repurposing, remanufacturing, or material recycling can be applied. In this context, remanufacturing is the favored end-of-use strategy to enable a new use cycle of lithium-ion batteries and their components. The process of remanufacturing itself is the restoration of a used product to at least its original performance by disassembling, cleaning, sorting, reconditioning, and reassembling. Thereby, disassembly as the first step is a decisive process step, as it creates the foundation for all further steps in the process chain and significantly determines the economic feasibility of the remanufacturing process. The aim of the disassembly depth is the replacement of individual cells to replace the smallest possible deficient unit and not, as is currently the case, the entire battery module or even the entire battery system. Consequently, disassembly sequences are derived from a priority matrix, a disassembly graph is generated, and the obstacles to non-destructive cell replacement are analyzed for two lithium-ion traction battery systems, to analyze the distinctions between battery electric vehicle (BEV) and plug-in hybrid electric vehicle (PHEV) battery systems and identify the necessary tools and fundamental procedures required for the effective management of battery systems within the circular economy.

Laser Sintering (LS) was the first Powder Bed Fusion (PBF) method for polymers and it is now quite an established process for rapid prototyping and even for the production of functional parts. High Speed Sintering (HSS) is a variant of PBF which was later developed and it has the potential to be more scalable than LS. Most of the work for HSS and LS has been conducted with polyamide-12 (PA 12). This work reports the first effort to use polyethylene terephthalate (PET) in HSS. Well defined, simple and complex parts could be printed without any build failures. However, limitations were induced by current HSS machines which led to some curvature (warpage) in tensile bars after manufacturing. The reason for this was that all currently available machines for HSS are built for polymers such as polyamide 12, which means their maximum bed temperature is limited to 190 °C. This corresponds to the lower limit of processability of PET in PBF processes. The slightly curved tensile bars were straightened by heating them to 230 °C with a weight on top, and afterwards the mechanical properties were measured. The tensile modulus was similar to what was obtained with PET via LS but the strength and elongation-at-break (EAB) was lower. Microscopy showed that the reason for the lower strength and EAB was the incomplete melting of particles. This arose from the temperature limitation of the current generation of HSS machines. The porosity was established as 2.23% by helium pycnometry which is the same as for LS. The results of the thermal analysis indicated that the PET parts manufactured with HSS were semi-crystalline like the PET parts manufactured via LS.

High Speed Sintering (HSS) is an additive manufacturing process with great potential to produce complex, high-quality polymer parts on an industrial scale. However, little information is currently available on the characteristics of the powder materials used and the part properties that can be achieved. This is also the case for the standard material polyamide 12 (PA 12) and the first commercially available HSS machine, the VX200 HSS. The aim of this study is, therefore, to provide the first comprehensive overview of the properties of PA 12 parts manufactured with the VX200 HSS and the characteristics of the PA 12 powder. This includes the analysis of the influence of part orientation and part position in the build job. To characterize the powder, particle size distribution, particle shape, thermal properties and powder flowability were analyzed. To characterize the parts, density and various thermal, mechanical and geometrical properties were analyzed. In summary, the powder material and part properties are largely similar to those of other Powder Bed Fusion of Polymer (PBF/P) processes. However, there are also significant differences for some part properties. It was also determined that the anisotropy of parts is very low compared to that of many other additive manufacturing processes.