Additive manufacturing for the automotive industry: on the life-cycle environmental implications of material substitution and lightweighting through re-design

The automotive sector has recently been taking measures to reduce fuel consumption and greenhouse gas emissions for the mobility of ground vehicles. Light-weighting, via material substitution, and the re-designing of components or even a combination of the two, have been identified as a crucial solution. Additive manufacturing (AM) can be used to technologically complement or even replace conventional manufacturing in several industrial fields. The enabling of complexity-for-free (re) designs is inherent in additive manufacturing. It is expected that certain benefits can be achieved from the adoption of re-design techniques, via AM, that rely on topological optimisation, e.g., a reduced use of resources in both the material production and use phases. However, the consequent higher specific energy consumption and the higher embodied impact of feedstock materials could result in unsustainable environmental costs. This paper investigates the case of the light-weighting of an automobile component to quantify the outcomes of the systematic integration of re-designing and material substitution. A bracket, originally cast in iron, has been manufactured by means of a powder bed-based AM technique in AlSi10Mg through an optimized topology. Both manufacturing routes have been evaluated through a comparative Life Cycle Assessment (LCA) within cradle-to-grave boundaries. A 69%-lightweighting has been achieved, and the carbon dioxide emissions and energy demands of both scenarios have been compared. Besides the use-phase-related savings in terms of both energy and carbon footprint due to the lightweighting, the results highlight the environmental trade-offs and prompt the consideration of such a manufacturing process as an integral part of sustainable product development

A comparative LCA method for environmentally friendly manufacturing: Additive manufacturing versus Machining case

Additive Manufacturing (AM) technologies revolutionized the common understanding of manufacturing with their layer-by-layer building principle. However, the literature has documented their high energy requirements, which is not in-line with the current policies of energy and emission reduction. This ambivalence of AM opens the question for the research community about the wise choice of the manufacturing process to be adopted. This paper proposes a comparative LCA method to select the best manufacturing technology between Conventional Manufacturing (CM) and EBM plus Finish Machining (EBM+FM). The Life Cycle Assessment (LCA) is conducted under cradle-to-gate boundaries. Three metrics, namely the Cumulative Energy Demand (CED), cost and CO2 emissions are considered. Characterization of unit processes is done by using the recent findings in the literature which are included in the model for both process technologies. The Specific Energy Consumption (SEC) is connected to the Material Removal Rate (MRR) and to the average Deposition Rate (DRa), respectively for machining and EBM. The main finding of this research is the description of breakeven surfaces, which separate the regions of validity between machining and EBM, as function of the Solid-to-Cavity Ratio (SCR) and the DRa. Moreover, the presented methodology gives the possibility to compare the goodness of the different sets of design rules that can be chosen for EBM, thanks to the proper evaluation of the SEC parameter. Finally, a sensitivity analysis is conducted to assess the effect of the remaining key variables

diamond drilling of carbon fiber reinforced polymers influence of tool grit size and process parameters on workpiece delamination

Abstract The physical and mechanical properties of advanced composite materials promote their application in structural components for the aerospace and automotive sectors. However, limitations in their machinability are due to anisotropy/inhomogeneity, poor plastic deformation, and abrasive behavior. For CFRP drilling, the process efficiency is heavily influenced by cutting conditions and tool geometry. This paper reports the outcomes of experimental diamond drilling tests. A 4-mm thick carbon-epoxy composite laminate was machined. The plate was made of ten layers, in which the carbon fibers were intertwined at 90°. 6-mm diameter core drills were used. Core drills were characterized by an electroplated bond type and an AC32-H diamond grain type. Four different tool grit size ranges were tested: (1) 63/53 μm, (2) 125/106 μm, (3) 212/180 μm, and (4) 212/180 plus 63/53 μm. The results are reported in terms of workpiece delamination, thrust force, torque, and chip morphology. Overall, the results allow identifying the cutting conditions for the minimum drilling-induced delamination while retaining a satisfactory process productivity

laser powder bed fusion l pbf additive manufacturing on the correlation between design choices and process sustainability

Abstract The specific energy consumption of Additive Manufacturing (AM) unit processes for the production of metal parts could be much higher than that of more traditional manufacturing routes, such as machining. However, AM, due to its intrinsic process peculiarities, including the flexible realization of (almost) any kind of complex shape, has a great potential for improving the material use efficiency, with positive environmental impact benefits from the material production to the product use and disposal at the end of first life. Aim of this paper is to assess the role of the design choices on the environmental AM process sustainability. An integrated design methodology (accounting for the product re-design via topological optimization, the design of support structures, and the design of allowances and features for post-AM finishing operations) for components produced by means of laser powder bed fusion processes is considered. One resource (the cumulated energy demand) and one emission (carbon dioxide) are assumed as metrics for the impact assessment across the product life cycle. The results demonstrate the importance of a proper design for AM to improve the overall energy and emission saving potential

Milling and Turning of Titanium Aluminides by Using Minimum Quantity Lubrication

AbstractWhen machining difficult-to-cut materials, the high temperature in the cutting area is one of the dominating phenomena affecting tool wear and process capability. Hence, cutting fluids are profusely used for cooling and lubrication purposes, in order to obtain satisfactorily process performances. The use of conventional fluids creates several problems, such as the environmental pollution due to chemical disassociation at high cutting temperatures, water pollution, soil contamination during disposal, and biological problems to operators. The implementation of green machining strategies to accomplish the increasing pressures for sustainability is therefore an open challenge for manufacturers and researchers. Aim of this paper is to evaluate the influence of the lubrication strategy on tool wear, surface quality and environmental impact when milling and turning Ti-48Al-2Cr-2Nb (at. %) intermetallic alloys. The workpieces were obtained by means of two production processes: vacuum arc remelting and electron beam melting (EBM). Coated carbide tools were used in cutting tests under different lubrication conditions. The results of dry cutting are compared to that of wet and minimum quantity lubrication (MQL) conditions. Overall, the experimental tests show that dry machining requires a sensible reduction of process parameters to preserve a stable process, although limiting the energy consumption and reducing to zero the lubricant consumption. Under the chosen cutting conditions, MQL appears to be an advantageous solution for milling, whilst in turning wet cutting is the best choice for reducing the tool wear, since the higher process temperatures require the higher cooling effect of the emulsion

A Contribution on the Modelling of Wire Electrical Discharge Machining of a γ-TiAl Alloy

AbstractWire electrical discharge machining (WEDM) is a manufacturing process suitable for high-precision cutting of complex and irregular shapes through difficult-to-machine electrically conductive components. In recent years, wire EDM has become a key non-traditional machining process, widely used in the aerospace and automotive industry. Although this technology has been broadly investigated, literature is still limited on the use of wire EDM for intermetallic alloys, and the applications on gamma titanium aluminides are rather unexplored. Such materials are attracting considerable interest due to the outstanding combination of properties, and they have proved to be eligible for thermo-mechanically stressed parts of aeroengines. Nevertheless, the poor machinability of gamma titanium aluminides has been reported in conventional (i.e. turning, milling, and drilling) and non-conventional machining, such as ECM. Further, machinability results strictly depend on the chemical composition of the specific alloy. This paper investigates the interactions between common process parameters of WEDM and final quality of the generated surface, through analysis of variance (ANOVA) and regression models based on experimental results. In particular, the paper is focused on the effects of pulse on time, pulse off time, servo-reference voltage, and wire tension on the surface finish during the WEDM of a Ti-48Al-2Cr-2Nb (at. %) γ-TiAl alloy. Results are discussed and compared with reference to the models available in literature

An appraisal on the sustainability payback of additively manufactured molds with conformal cooling

The use of Additive Manufacturing (AM) in the production of tooling for injection molding has led to the introduction of conformal cooling as an effective way to lower the cycle time of the process. As the cooling cycle is responsible for a large portion of the energy consumed during the injection molding process, conformal cooling allows increasing the energy efficiency. However, AM could create a large upfront cost of energy for the manufacturing phase. This paper investigates a case study where a cradle-to-grave life-cycle assessment is used to evaluate the cumulative energy demand of conventional or conformal cooling molds

A structured comparison of decentralized additive manufacturing centers based on quality and sustainability

Companies are increasingly adopting decentralized manufacturing strategies to manage multiple, geographically scattered manufacturing centers that are characterized not only by similar types of equipment, working methods, and productions, but also by variable mixes and volumes. This trend also applies to additive manufacturing, a well-established technology that allows the flexibility and customization of production to be increased, without significantly increasing the per unit cost. Thus, the need arises to monitor the performance of individual centers in a structured way, and to make practical comparisons of such centers. However, achieving this task is not so straightforward, given the inevitable differences in the characteristics of manufacturing centers and their productions. This paper presents a methodology that can be used to analyze and com-pare the production performance of a plurality of manufacturing centers from two different viewpoints: (i) quality, through a multivariate statistical analysis of product data concerning conformity with geometrical specifications, and (ii) process sustainability, with the aim of achieving a reduction in energy consumption, carbon dioxide emissions, and manufactur-ing time, through regression models pertaining to the selected metrics. The proposed methodology can be adopted during regular production operations, without requiring any ad hoc experimental tests. The description of the method is supported by an industrial case study

Additive manufacturing for an urban vehicle prototype: re-design and sustainability implications

Additive Manufacturing (AM), allowing the layer-by-layer fabrication of products characterized by a shape complexity unobtainable with conventional manufacturing routes, has been widely recognized as a disruptive technology enabling the transition to the Industry 4.0. In this context, the design of a Portable Assisted Mobile Device (PAMD) prototype was considered as a case study. The best practices of the re-design for AM were applied to three of the main structural components, and the most sustainable manufacturing approach between AM processes and the conventional ones was identified with respect to cumulative energy demand, carbon dioxide emissions and costs. The paper aims to promote the debate concerning the correlation between design choices, process selection and sustainable product development

Multi-criteria environmental and economic impact assessment of wire arc additive manufacturing

Wire arc additive manufacturing (WAAM) is a fusion- and wire-based additive manufacturing technology which has gained industrial interest for the production of medium-to-large components with high material deposition rates. However, in-depth studies on performance indicators that incorporate economic and environmental sustainability still have to be carried out. The first aim of the paper has been to quantify the performance metrics of WAAM based manufacturing approaches, while varying the size and the deposited material of the component. The second aim has been to propose a multi-criteria decision-analysis mapping to compare the combined impacts of products manufactured by means of the WAAM-based approach and machinin