Procedia CIRP最新文献

Due to the long-life span of railway vehicles, spare part availability is a major challenge for railway companies. To avoid downtime, high procurement costs, and shortages, railway companies often stock large and costly inventories. However, additive manufacturing (AM) makes it possible to cost-effectively produce spare parts in small quantities to reduce inventory. To assess the suitability of a spare part and choose the optimal supply strategy, economic and technical data must be available in good quality. The lack of centralised information and poor data quality is one of the biggest challenges for AM potential assessment.

A workflow was designed, in which system data from various databases was mapped and enhanced with technical information. In addition, the potential for additive manufacturability was evaluated based on costs and savings affected by transportation, design, manufacturing, storage compared to other supply strategies. The resulting database was then used to classify the spare parts based on specific characteristics. The defined classes provide information about the timeline for implementing the part and the type of application. A similarity check based on identified AM spare parts is used to search the entire database to identify additional potential AM parts. The result is a data-driven framework to conduct a holistic potential assessment for additive manufacturable spare parts.

To establish a circular manufacturing system, continuous management of the resource flow and the condition of individual items including products, components, and the materials in the system is indispensable. This study proposes a life cycle simulation (LCS) based management method to support optimal decision-making under conditions that include various uncertainties, such as consumer behavior and market trends. LCS is a simulation method that simulates dynamic material flow in the entire life cycle system and enables the evaluation of environmental and economic efficiencies. Since the simulation model consists of many parameters, exhaustive simulations with all parameter combinations are impossible in a practical timeframe. Therefore, the method extracts parameters that have a significant impact on eco-efficiency through sensitivity analysis using LCS. Then, a response surface of multi-level resolution is created in a multidimensional space composed of the parameters. The response surface is used to quickly identify optimal parameter values under uncertain conditions for effective management. As a case study, the proposed method is applied to the management of a circular manufacturing system for lithium-ion batteries of automotive to verify the effectiveness of the management on eco-efficiency.

Digital battery passports are a potentially helpful tool to facilitate the recycling of lithium-ion batteries. This is due to the information asymmetry between battery producers and end-of-life (EoL) actors. Tailoring a battery passport to EoL offers the opportunity to go beyond the current state of the art of battery passport legislation and add further details that are important for the recycling process. Therefore, this research looks at a suitable way to set up a battery passport to support the EoL of lithium-ion batteries. First, the data needs of the EoL phase were analyzed based on use cases described by eight experts through interviews. The results show a need for material related- and dynamic data, such as the state of health. The same expert interviews were then used to answer how these needed data could be provided. The results confirm the availability of most data but with gaps regarding dynamic data and use-phase information. Both the data needs and provision are then categorized and summarized into a data model. The discussion also provides an overview of the challenges and estimates the impact, depending on the scale of implementation. The results were used to set up a prototype platform for a battery passport.

Material recycling is an essential lever for improving the sustainability of production processes. One way of reusing metal chips that occur as waste in machining or other subtractive manufacturing processes is to mechanically pretreat and remelt them. In mechanical pretreatment, the chips are separated from the cutting fluid by a centrifuge and then briquetted directly on site. This simplifies the handling and makes the transport and subsequent remelting more efficient than in thermal processing alone. The main objective of this work is to quantitatively assess the environmental impacts of the described recycling process, focusing on the global warming potential. Furthermore, recycling by means of mechanical chip processing is compared with alternatives such as thermal drying and primary material extraction. A parametric life cycle assessment (LCA) model has been developed for this purpose. The model considers equipment, material, throughput and location variations to analyze different use cases. The results of the LCA of an exemplary use case show that environmental benefits result from a higher bulk density during transport and a lower energy input during remelting due to a lower liquid content.

Laser Metal Deposition (LMD) allows the fabrication of complex shapes onto non-planar surfaces. This manuscript presents a 3D-scanning strategy for the dimensional inspection of LMD-manufactured gear teeth onto cylindrical substrates. The standard registration (alignment) methods are ineffective in the context of LMD because they minimize the global distance between the reference model and the 3D-scanning point cloud. This global minimization wrongfully biases the alignment. In response to this limitation, this manuscript discusses a registration procedure that avoids global distance minimization by sequentially aligning the datums (gear root cylinder and planar faces) of both datasets. This datum-alignment procedure fixes 5 out of 6 Degrees of Freedom (DOF). The final DOF is determined by finding the optimal rotation angle that minimizes the distance between the gear teeth of both datasets. The strategy is validated with actual LMD-manufactured spur and helical gear teeth onto cylindrical substrates. This strategy would also save time during the grinding process.

Beam shaping of lasers is a topic that has received relatively less attention in the context of metal additive manufacturing (MAM) processes. This technique allows for modulation or spatial alternation of the intensity profile of the laser. As the bulk of the work within MAM primarily revolves around Gaussian beam profiles, the precise impact and potential of other beam shapes is still an unanswered question. In this work a multiphysics numerical model of the laser powder bed fusion (LPBF) process of Ti6Al4V without powder is developed and the model can predict thermo-fluid-microstructural conditions. The model predictions are compared with experimental data from single-track specimens, and the comparison shows a very good agreement. It is shown that the ring spot beam profile (RSBP) results in substantially wider melt pools as compared to the ones forming using the Gaussian beam profile (GBP). The microstructural predictions show that for GBP the grains converge to the center line of the melt pool, while for ring beam profile (RBP), the grains tend to converge to a single point. Finally, the impact of different ring radii for RBP is studied and the results show that at larger ring radii, a noticeable bulge of liquid metal forms right beneath the laser beam.

Welding of high-alloy steels results in spatter formation addressing high welding speeds above 8 m/min, i.e., the seam quality is significantly reduced due to material losses and adhering spatter. A reduction of spatter can be addressed by using concentric intensity distributions consisting of core and ring, by affecting melt and metal vapor flow. In this paper, the understanding of spatter formation on sheet top and bottom side is significantly enhanced for full penetration welds of AISI 304. Therefore, different concentric intensities and tophat distributions were systematically studied and compared. Fundamental interactions between concentric intensity distributions and spatter formation during full penetration welding were determined and summarized in model concepts. In particular, spatter formation can be reduced on both sheet sides using a concentric intensity distribution due to a smaller keyhole geometry with a smaller angle of inclination of the keyhole front.

Laser-based powder bed (PBF-LB) fusion of polymers has emerged as a versatile technique for additive manufacturing (AM), offering laynew processing freedom through promising beam-shaping techniques. This study explores a novel approach to overcome the NIR absorption limitations of the market-dominant standard material polyamide 12 (PA12) by increasing the sensitivity for effective diode laser processing through surface modification with NIR-absorbing nanoparticles (NPs). The investigation encompasses nano sensitization strategies and theoretical analysis of energy input to the polymer, alongside comparisons with volume-modified polymer feedstocks, demonstrating that diode laser printing of surface-modified (s-mod) PA12 is possible with a macroscopic quality comparable to a commercially available volume-modified (v-mod) feedstock.

Today, complex structural components for lightweight applications are frequently manufactured by laser powder bed fusion (PBF-LB), often using aluminum alloys such as AlSi10Mg. However, the application of cyclic load cases can be challenging as PBF-LB produced AlSi10Mg parts typically have low ductility and corresponding brittle failure behavior in the as-built condition.

Therefore, this paper presents investigations on the feasibility of a laser heat treatment of PBF-LB produced AlSi10Mg parts to locally increase the ductility and decrease the hardness in critical areas. Potential heat treatment process parameters were derived theoretically based on the temperature fields in the material calculated assuming three-dimensional heat conduction and a moving heat source. PBF-LB produced specimens were then laser heat treated at varying laser power and scan speed. Hardness measurements on metallographic cross sections showed hardness reductions of over 35 % without inducing hydrogen pore growth.

In laser-based powder bed fusion of metals (PBF-LB/M), the atmospheric residual oxygen plays a key role, particularly for highly reactive materials like Ti-6Al-4V. Oxygen concentrations present in commercial machines are still too high to effectively prevent oxidation of the powder and oxygen take-up into built parts deteriorating the part quality and mechanical properties. In this work, to reduce the residual oxygen content to a range adequate to an extreme high vacuum (XHV) while maintaining normal pressure, a silane-doped argon atmosphere (< 0.001 vol.-% silane in argon) is introduced. Ti-6Al-4V powder was processed both under a conventional argon atmosphere (< 0.01 vol.-% oxygen) and argon-silane atmosphere (< 10^-20 vol.-% oxygen). The influence on the resulting porosity was investigated using a central composite design. Additionally, the tensile properties were analyzed. High tensile strengths > 1290 MPa and low porosities < 0.02 %, but no significant influence of the atmosphere was found.