Energy efficiency and circular economy implications of additive manufacturing

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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

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

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

Sustainability Assessment of Additive Manufacturing Processes

Additive Manufacturing (AM) processes were developed in the 1980s to reduce the time for the realization of prototypes. Nowadays, AM processes are considered as real manufacturing techniques suitable to build end-use products. As for any new technology, research efforts aiming to process planning and optimization within a sustainable development framework are needed. In particular, the application of the sustainable manufacturing principles requires the creation of products that use processes that minimize negative environmental impacts, conserve energy and natural resources, are safe for employees, communities, and consumers, and are economically sound. In this work, the three aspects of sustainability, namely environmental, economic and social sustainability are critically analyzed for AM. For each topic, an analysis of models that can evaluate the consumption of energy and CO2 emissions, costs and the impact on workers' health is carried on. The functional redesign of a mechanical object, with the aim of reducing its mass and trying to keep unchanged the constraint conditions imposed is accounted for. A critical analysis of the impacts on workers' health focusing on the hazardous aspects related to the animal and human exposure to metal powders is presented. Considerations on body weight, cancer, cardiovascular, dermal, endocrine, gastrointestinal, hematological, hepatic, musculoskeletal, neurological, ocular, rheumatologic, renal, reproductive, respiratory effects are reported for different elements as Cobalt, Chrome, Nickel, Titanium and for each kind of exposure (inhalation, oral, dermal). Methods for the comparison and evaluation of an inventory s dissimilar pollution loads have been proposed and are critically analyzed. Considerations on the possible workplace maintenance techniques to be followed for handling metal powders (such as those according to ASTM, NFPA and OSHA standards) are also evaluated. Whatsoever, it is possible to consolidate a new technology in the industrial scenario only if it is economically sustainable and profitable. A critical study of the evolution of the main economic models is reported. In addition, approaches that can take into account also the pre-process and post-process phases as well as the production of different objects in the same built are presented. Moreover, in this work, several examples and comparisons of the sustainable performance of different AM techniques are discussed. A critical study of models that can evaluate the amount of CO2 emissions during the production of part via AM techniques is studied. A model for the calculation of CO2 emissions from the consumption of electricity is also detailed. The above mentioned models have been applied to selected case studies before and after the redesign phase. NX and ANSYS software were used to perform the geometrical optimization. An experimental study was then conducted to validate the results

The Role of re-design for Additive Manufacturing on the Process Environmental Performance

At present, economic and technological design criteria for products and processes should be matched with the minimization of environmental impact objectives. Manufacturing, material production, and product design are strictly connected stages. The choice of a production system over another could result in significant material and energy/resource savings, particularly if the component has been properly designed for manufacturing. In this scenario, Additive Manufacturing, which has been identified as a potential disruptive technology, gained an increasing interest for the creation of complex metal parts. The paper focuses on the tools, based on the holistic modelling of additive and subtractive approaches, which could be used to identify the production route allowing the lowest energy demand or CO2emissions. The models account for the main process variables as well as the impacts due to the re-design for AM for the creation of components made of Ti-6Al-4 V

Methodology for Commodity Cost Estimation Through Production Line Analysis and Simulation

In a growing competitive environment, it is essential to have a clear idea of a product’s total expenditure by estimating the component costs and correctly allocate cost drivers. Assigning exact commodity consumption costs is one of the most complicated aspects of cost engineering activities, which should be performed during the product design stage using Product Lifecycle Management (PLM). However, during the design stage, information is not complete, and it is not sufficient to guarantee the cost estimate’s adequacy and reliability. Therefore, it is necessary to monitor the production process to identify each cost variable carefully. This article aims to propose a methodology to evaluate the proper commodity consumption during manufacturing activities for the assessment of the total part cost. Moreover, it helps to generate validated data useful for decision support systems. The proposed approach is studied by analyzing a machining production line of an Italian manufacturer of components for the automotive industry. It consists of three main parts: (i) description of the production line, (ii) definition of IT architecture, and (iii) asynchronous digital twin design. Thus, after the model’s validation, the simulated data allows to analyze and estimate production expenditure accurately by the exact allocation of commodity consumption

Sustainability in the manufacturing of composite materials: A literature review and directions for future research

Composite materials showed great potential in replacing metal components in several applications allowing adequate component strength with reduced weight. From a sustainability point of view, a significant number of studies demonstrated that a component made of composite materials is one of the best responses to the recent global legislation for the reduction of energy consumption and CO2 emissions. The sustainability of the production of composite components should be assessed by structured approaches that consider the whole life cycle of the component from the raw material production, the manufacturing process and post processes to the end-of-life (EoL). The purpose of this paper is to present the state-of-the-art life cycle inventory (LCI) data available in the literature for a composite product. Works evaluating the embodied energy of the most common fibres and polymeric matrixes are collected. Each manufacturing technique is reviewed regarding energy efficiency by considering the specific energy consumption (SEC). Among the potentialities which characterise the EoL of a composite product, a focus is given to the recycling techniques. Future research challenges are proposed and discussed. The outcomes revealed a considerable dispersion in embodied energies and SEC values for both the reviewed materials and technologies. The SEC is the only descriptor for process efficiency. However, there is a lack of investigation into the relationship between the process parameters, processed materials, component size and energy consumption. In particular, for additive manufacturing processes, no data were found. In addition, the literature on using natural fibres as a sustainable alternative and recycling methods and their impact is extremely limited