Maximizing Energy Efficiency in Additive Manufacturing: A Review and Framework for Future Research

Abstract

Additive manufacturing (AM) offers unique capabilities in terms of design freedom and customization, contributing to sustainable manufacturing. However, energy efficiency remains a challenge in the widespread adoption of AM processes. In this paper, we present a comprehensive review of the current research on energy efficiency in AM, addressing challenges, opportunities, and future directions. Our analysis reveals a lack of standardization in the measurement and reporting of energy consumption, making it difficult to evaluate and compare the energy performance of various systems. We propose a holistic framework to address energy efficiency throughout the entire life cycle of the AM process, highlighting the importance of design optimization, material selection, advanced control systems, and energy management strategies. The paper also emphasizes the need for further research on the interactions between process parameters, along with the potential of integrating renewable energy sources into AM systems. This review offers valuable insights for both academics and industry professionals, calling for standardized methodologies and a focus on energy management to optimize energy efficiency in AM processes, ultimately enhancing competitiveness and sustainability in modern manufacturing.

1. Introduction

Broadly speaking, energy efficiency can be understood as the practice of utilizing a reduced quantity of energy to generate an equivalent amount of services or beneficial output [1]. Energy efficiency (EE) in manufacturing is the capacity of a system or process to consume less energy, while maintaining or enhancing performance [2,3]. Governments and organizations often prioritize energy efficiency as a means to achieve sustainability goals and reduce the environmental impact [4]. The utilization of energy during the additive process of fabricating three-dimensional objects is the subject of EE in additive manufacturing (AM) [5]. AM is a collection of techniques that create an object, often under the control of a computer, by adding material in a sequential manner. This can include layer-based processes, but also other methodologies, reflecting the broad spectrum of technologies within the AM field [6]. Three-dimensional printing and additive manufacturing terms are mostly used to describe the same technology. However, there is a slight distinction between the two terms [7]. Many procedures and technologies that construct an object layer by layer fall under the umbrella name of additive manufacturing (AM) [8]. Additive manufacturing encompasses a range of techniques, including 3D printing and other specific methods such as fused deposition modeling, among others. Basically, additive manufacturing is any manufacturing technique that involves adding material to produce a product rather than removing material through operations such as machining or molding [9]. AM offers several advantages compared to traditional manufacturing techniques, including the ability to produce complex, custom-designed shapes and structures with minimal waste [10,11,12,13,14]. Given that it can significantly affect the cost and environmental impact of the manufacturing process, the EE of this process is a crucial factor to consider [15,16,17]. There are several factors that can affect the EE of AM [18,19,20]. Among these, the type of machine employed significantly impacts energy efficiency. Energy efficiency in 3D printing is impacted by various factors, including the energy source, printer size and weight, and the materials processed. The design of the printed object also influences energy usage, but it is crucial to consider this in relation to the amount of material deposited, as larger or more complex designs naturally require more energy. However, the key measure of efficiency is the energy consumed per unit of material deposited. There are few ways that can be used to enhance the EE of AM [21], including to the improve printed product design, use more energy-efficient 3D printing equipment, and utilize energy-saving manufacturing techniques. Research is ongoing to develop new technologies and materials that can improve the EE of AM. Hence, improving the EE of AM is important for both economic and environmental reasons [22]. AM typically necessitates less energy per unit produced compared to traditional methods, given its ability to reduce waste and create complex geometries without additional machining. This energy efficiency, coupled with the wider accessibility of products, can result in lower overall manufacturing costs [23]. AM can also minimize the negative impacts on the environment by cutting greenhouse gas emissions [24].

At its core, additive manufacturing (AM) is recognized for its capacity to create customized parts from a variety of printing materials [25]. Traditional production processes often involve cutting and shaping materials, leading to substantial waste and potentially less energy efficiency compared to AM. However, energy consumption remains a critical factor in the development and management of AM systems [26]. Energy must be utilized during the AM process to heat and/or solidify the material being printed, and the amount of energy required will depend on the machine and the materials being used. The energy needed to run the computer-controlled printer and any other machinery, such as curing lamps or sintering ovens, must also be considered. As a result, the EE of AM systems is crucial to take into account, both from a financial and environmental point of view. Designers and manufacturers must take into account a variety of elements, including the type of machine being used, the materials being processed, and the design of the object being printed, in order to enhance the EE of these systems [27].

Energy efficiency in additive manufacturing (AM) plays a crucial role in meeting sustainable development and environmental protection goals [28]. As industries across the globe strive to reduce their environmental impact and minimize resource consumption, enhancing energy efficiency in AM processes becomes increasingly important [29]. By optimizing energy usage in AM, industries can reduce their carbon footprint, decrease operational costs, and contribute to a more sustainable future [30]. Previous literature has emphasized the significance of energy efficiency in manufacturing sectors, and our review aims to build on this foundation, specifically focusing on the AM domain.

Within the last decade, the AM sector has grown significantly. However, this development has led to an increase in energy consumption and greenhouse gas emissions. The manufacturing industry, including additive manufacturing, is responsible for 38 percent of the total world energy consumption and even a larger portion of the GHG emissions [31]. AM processes, particularly those using metal, may be energy-intensive, leading to significant GHG emissions. Given the increasing development of the AM industry, energy consumption and accompanying emissions might skyrocket if proper energy efficiency measures are not implemented. As a result, maximizing energy efficiency in AM is more than simply an issue of lowering operational expenses; it is also an important component of the worldwide effort to counteract climate change.

There are several further motivations for conducting a review of the state of research on the topic EE in AM. A review can help to spot patterns and developments in the literature, point out areas that may require more research, highlight knowledge gaps, and offer the best practices and guidelines for enhancing EE of AM processes. Overall, a review can offer insightful information and help direct future study and practice in this significant area. The type of energy used, the amount of energy consumed, the process efficiency, the waste generated, and the environmental impact are therefore some of the important factors that might affect the EE of AM processes, and they will all be covered in this article. We may better understand the EE of AM processes and find areas for development by taking into account these aspects.

The purpose of this research is to present a comprehensive framework for comprehending and optimizing energy efficiency in additive manufacturing. We identify the important AM process parameters that directly or indirectly affect energy efficiency, and we propose techniques for enhancing energy efficiency at each stage. To achieve optimal energy efficiency, we emphasize the necessity of examining the entire life cycle of the AM process, from design through to material selection, slicing, and post-processing.

In addition to the framework, we review the current state of research on energy efficiency in AM, identifying the gaps and limitations in recent studies. By providing a holistic approach to energy efficiency in additive manufacturing, we aim to pave the way for future research and practical applications, ultimately fostering a more energy-efficient and sustainable manufacturing industry.

The objectives of our review study are:

• To identify the trends and advancements relating the combined topic of AM and EE, including the most widely used methods and tools, the materials under investigation, and the main difficulties and opportunities in this area.
• To discover gaps in the existing body of knowledge, and highlight areas that require more research.
• To present a framework and guidelines for improving the EE of AM processes.
• To offer a thorough overview of the state-of-the-art in research on EE in AM, including the key findings and insights from existing studies and the implications for future research and practice.

The manuscript is structured as follows: after the introduction in Section 1, Section 2 compares the relevant reviews of EE in AM. The methodology for the review is presented in Section 3, while the results of the bibliographic analysis are presented in Section 4. Recurrent topics and gaps in the available research are identified in Section 5. In Section 6, we present a novel framework to classify topics in EE analysis for AM. Finally, in Section 7, conclusions are drawn and directions for future work are proposed.

2. A Comparison with Earlier Literature Reviews and the Driving Force behind This Study

Previous state-of-the-art analysis studies on the combined topic of additive manufacturing and energy efficiency have been limited to a few literature reviews. In this section, we present a comprehensive overview of these previous studies, including their content and contributions. We then proceed to highlight the differences and unique contributions of our review work in comparison to existing literature. This analysis serves to demonstrate the need and motivation for the present study, which provides a comprehensive and up-to-date examination of the field.

The field of additive processing technologies was the focus of Gutowski et al.’s (2017) study, which looked at the process rates and energy intensities of various technologies and highlighted recent advancements in these metrics [32]. The advancements in the processing of polymers and composites using filament and pellet extrusion, as well as laser-powder bed fusion of metals, are specifically highlighted by the authors. They point out that over the past ten years, there have been significant improvements in raw build rates, with polymer extrusion processes improving by more than two orders of magnitude, and laser metal processes by about one order of magnitude. The authors have also created straightforward heat transfer models that highlight rate limits, identify additional potential improvement strategies, and assist in explaining these advancements. They find that the development of laser metal technologies follows a pattern similar to that of machine tools, with faster rates requiring more power without a change in energy or rate efficiency. Overall, the authors’ contribution provides valuable insights into the current state and future directions of additive processing technologies.

The field of metal additive manufacturing and evaluations of environmentally friendly manufacturing has benefited greatly from the work of [15]. First, they have examined the energy usage of metal additive manufacturing over the course of a printed product’s life cycle. This analysis offers insightful information about this manufacturing process’s overall energy footprint. The authors have also covered the effects of eco-manufacturing metal products on society, the economy, and the environment. This investigation clarifies the advantages of using more environmentally friendly manufacturing techniques in the metal industry. The potential for energy consumption optimization and the future course of energy-saving in metal additive manufacturing have also been projected by the authors. For business professionals looking to cut their energy consumption, these projections offer useful information.

Through a thorough review of the available literature, [33] examined the field of metal additive manufacturing (MAM), with a focus on energy and material efficiency in the aerospace/aeronautic industry. Based on various MAM life cycle stages, including product design, material development and sourcing, process development and optimization, end-of-life extension, and circular economy, the authors have organized and discussed the pertinent literature. This classification offers insightful information into the essential elements needed to optimize MAM and evaluate its environmental impact in comparison to traditional manufacturing techniques. The review’s findings demonstrate the stark differences in material and energy efficiency among various MAM processes, which are influenced by both process-specific and supply chain variables such as the electricity mix. The authors propose that additional research could examine cutting-edge technological trends for circularity or multi-material MAM, which would improve the manufacturing process’s energy and material efficiency.

By outlining the limits of membrane production historically, Qian et al. (2022) investigated membrane technology [34]. After that, they discuss the most recent uses of additive manufacturing in this industry, giving a thorough overview of the most recent advancements and breakthroughs. The authors of this study also compare 3D printing to conventional methods in terms of important manufacturing metrics, and they offer a helpful analysis of the benefits and drawbacks of these various strategies. Alongside that, the authors provide future challenges and perspectives of 3D printing in membrane technology, offering insights into the future direction for this field. To sum up, the authors’ contribution provides a detailed literature review in this field and offers valuable insights into its future development.

Last, but not least, Alinejadian et al. (2022) looked at the processing of functional materials and energy conversion/storage systems using next-generation manufacturing techniques [35]. They focus on AM that provides new opportunities for experimentation with creative concepts and the production of sophisticated three-dimensional structures made of metals, ceramics, and composites. The authors investigate the application of a two-dimensional material with remarkable characteristics that makes it a possible choice for energy storage electrodes. They contrast modern AM techniques, especially laser-based powder bed fusion, with conventional processing techniques, and conclude that the latter can produce complex structures for various electrochemical applications. The authors’ contribution sheds light on the potential of additive manufacturing to provide energy-efficient, cost-effective, and eco-friendly solutions for processing functional materials with improved performance and functionality.

In several ways, our review of the literature on energy efficiency in additive manufacturing (AM) differs from previous reviews. The scope of the review is one significant difference. Previous review studies on the topic focused on specific aspects, such as energy consumption, during the printing process or the use of specific materials. Our review takes a more detailed approach, and covers several attributes related to EE in AM, such as energy consumption, energy management strategies, and the incorporation of renewable energy sources. Another distinction is the databases used for the literature searches. Previous reviews of the literature tended to rely on a single database, such as Scopus or Google Scholar. Our review, on the other hand, made use of three databases: Scopus, IEEE Explorer, and Engineering Village. Moreover, in our review, we used a more rigorous screening and paper selection process to guarantee the relevance and quality of the articles included in our review study. This included only using scientific articles from peer-reviewed journals that were complete, written in English, and related to manufacturing and energy efficiency. Review and generic articles were excluded from the final sample. Finally, our review provides a more up-to-date overview of the state of research on energy efficiency in AM, because it includes literature published up until 2023, whereas previous literature reviews may not be as recent.

3. Review Methodology

This study aimed to critically review the current state of research on energy efficiency in additive manufacturing processes. To gather the most relevant and high-quality literature, we utilized three databases: Scopus, IEEE Explorer, and Engineering Village. These databases were selected due to their extensive coverage of engineering and technology literature, as well as their focus on scholarly research and peer-reviewed publications.

We did a systematic literature review in this work, which is a type of research synthesis that employs a systematic strategy to collect secondary data, critically assess research papers, and qualitatively and/or quantitatively synthesize the findings [36,37]. This method is used because of its stringent research inclusion rules and methodical approach to reviewing and synthesizing the literature, which minimizes bias and allows for repeatability. We chose the systematic literature review process because it allows us to present a thorough and trustworthy overview of energy efficiency in additive manufacturing.

Our search query was carefully crafted to target the specific topic of energy efficiency in additive manufacturing processes, and was limited to the English-language peer-reviewed articles. We created our search query with the terms ‘additive manufacturing’ and ‘energy efficiency’ in the title, abstract, and keywords of the articles.

In our study, we used a specific keyword selection technique to ensure a thorough examination of the research in the field of additive manufacturing. We recognize that the terms “3D printing” and “additive manufacturing” are frequently used interchangeably in the literature. However, for the sake of this analysis, we picked “additive manufacturing” as our core term, since it incorporates processes other than 3D printing, such as selective laser sintering (SLS), fused deposition modeling (FDM), and stereolithography (SLA). While the word “3D printing” is widely used, it largely refers to a subset of additive manufacturing technologies; thus, we feel that the wider term “additive manufacturing” provides a more inclusive and accurate description of the existing literature in this topic. Additionally for our review, we only looked at journal publications, since they often go through a more rigorous peer-review process, which assures a greater degree of scientific rigor and depth. This decision was made to guarantee the accuracy and comprehensiveness of our review.

The search yielded a total of 173 results on Scopus, 166 publications on Engineering Village, and 10 articles in IEEE Explorer. To ensure the relevance and quality of the literature, a screening and paper selection procedure were applied. The authors meticulously examined each manuscript and eliminated the duplicates, resulting in 220 papers. Ultimately, 164 publications were included in our research, after a thorough and rigorous selection process. The method we used for screening articles is summarized in

Table 1. The method used for screening papers.

Databases	Article Type	Search Query	Screening and Paper Selection Procedure	Removal Criteria
Scopus, Engineering Village, IEEE Explorer	Publications in peer-reviewed journals	the terms ‘additive manufacturing’ and ‘energy efficiency’ in the title, abstract, and keywords of the articles	Publication in the manufacturing domain; English only; full paper is available; energy efficiency relevant	Review articles and generic articles removed

.

To reach the final sample of 164 papers for analysis, we employed a rigorous process to ensure the relevance and quality of our sources, leading to the following list [28,32,33,38,39,40,41,42,43,44,45,46,47,48,49,50,51,52,53,54,55,56,57,58,59,60,61,62,63,64,65,66,67,68,69,70,71,72,73,74,75,76,77,78,79,80,81,82,83,84,85,86,87,88,89,90,91,92,93,94,95,96,97,98,99,100,101,102,103,104,105,106,107,108,109,110,111,112,113,114,115,116,117,118,119,120,121,122,123,124,125,126,127,128,129,130,131,132,133,134,135,136,137,138,139,140,141,142,143,144,145,146,147,148,149,150,151,152,153,154,155,156,157,158,159,160,161,162,163,164,165,166,167,168,169,170,171,172,173,174,175,176,177,178,179,180,181,182,183,184,185,186,187,188,189,190,191,192,193,194,195,196,197,198]. Primarily, we ensured that each paper directly addressed the central focus of our review: energy efficiency in additive manufacturing. This provided a targeted pool of research that was most pertinent to our study. Secondly, we scrutinized the methodology employed within each paper. We prioritized papers that presented novel research, substantive data, or provided comprehensive reviews on the topic. This allowed us to focus on studies that offered significant insights and robust findings. This multifaceted selection process ensured the thoroughness and rigor of our literature review, and we believe it has bolstered the strength of our conclusions.

Together with the screening and selection process, we also conducted a more in-depth analysis of each publication in our literature sample using several important attributes as criteria. These attributes are:

• Distribution of articles by year.
• Purpose of the study.
• Type of additive manufacturing method (stereolithography (SLA); selective laser sintering (SLS); selective laser melting (SLM); fused deposition modeling (FDM); digital light process (DLP); multi-jet fusion (MJF); PolyJet; direct metal laser sintering (DMLS); electron beam melting (EBM); laser metal deposition (LMD); other; not stated).
• Industry applications: This includes the specific sectors where additive manufacturing is applied such as aerospace, automotive, healthcare, education, and more. The industry context can offer insights into specific energy efficiency challenges and opportunities.
• The scale AM is used (industrial, laboratory, prototyping, other, not stated).
• What material is used for AM?
• Quality inspection type (after printing, in-process, no quality inspection, not stated, other).
• Is energy consumption studied?
• Is energy optimization used? (Yes; No; Partially; Not stated). If yes, what methods are used? What are the results?
• Is the correlation between energy consumption and quality studied? If yes, what are the results?
• Is printing time optimization studied?
• Is sustainability considered? If yes, how?

The selected papers were also examined for information on additional factors, such as zero-defect manufacturing (ZDM) methods [199,200], the trade-off between energy consumption and traditional machining techniques, material reusability, consumables for additive manufacturing machines, and post-processing techniques, in addition to the main attributes analyzed. In order to direct future research in the area, the factors that led researchers and practitioners to choose additive manufacturing over conventional production processes were also evaluated.

By conducting this review, we increase knowledge in this area by providing an updated and comprehensive assessment of the current state of research on EE in AM. The findings of our study are significant for both researchers and industry professionals involved in additive manufacturing, as well as for decision-makers seeking to adopt energy-efficient procedures in the manufacturing business.

4. Results of Literature Analysis

4.1. Distribution of Articles by Year

We looked at the distribution of the selected articles by year to understand the temporal trend of research on energy efficiency in additive manufacturing. The number of publications per year is highlighted in Figure 1. The interest in the topic has grown over time, with 2022 recording the highest number of articles. This development shows how important and pertinent studying energy efficiency in additive manufacturing is becoming.

4.2. Distribution of Publications by the Purpose of the Study

By highlighting the most prevalent goals and their relative importance in the identified papers, we analyze various research focuses on the field of energy efficiency in additive manufacturing in this subsection. Hence, we looked at each study’s main goal. The printing process received the most attention, with 23.2% (38 papers) of the studies examining this topic. Sixteen papers (9.8%) focused on the investigation of printing materials, while 0.6% of the publications evaluated both printing materials and processes. Two publications (1.2%) were focused on parameter tuning. Twenty-six papers (15.9%) were devoted to the creation of energy consumption models. Three articles (1/8%) examined the optimization of the slicing process, whereas 12.8% (21 papers) examined the optimization of the printing process. One publication (0.6%) concentrated on printing monitoring and optimization, whereas two papers (1.2%) evaluated both the printing materials and processes. Seven articles (4.3%) examined the use of additive manufacturing to replace more conventional techniques. Design solutions for energy efficiency were looked in at 8.5% (14 articles) of the research articles, whereas 2.4% (four papers) of the studies focused on quality control. Nine papers (5.5%) were devoted to the development of prediction models, whereas 9.1% (15 articles) of the studies were devoted to printing analysis. Figure 2 summarizes the distribution of research objectives and sheds light on the numerous additive manufacturing applications that have been studied in the context of energy efficiency.

4.3. Overview of the Various Additive Manufacturing Methods

According to our study of the selected articles, many additive manufacturing techniques have been researched in relation to energy efficiency. The two technologies that were most commonly researched were selective laser melting (SLM), which received 18.9% of the total number of publications (31), and fused deposition modeling (FDM), which accounted for 17.1% of the total number of papers (28). (13 papers). Several publications (7.9%, 13 papers) did not specify a method. Ten papers (6,1%) were concerned with wire arc additive manufacturing and powder bed fusion additive manufacturing, respectively. Stereolithography (SLA) made up 4.9% of the research, while direct metal laser sintering (DMLS) made up 5.5% (nine publications). A lesser degree of coverage was also given to other techniques, such as fused filament fabrication (3.7%, six articles), electron beam melting (EBM) (3.0%, five papers), PolyJet (1.8%, three papers), and laser cladding (1.8%, three papers). The 18 publications that were left out (11.0%) looked into various additional techniques. Figure 3 summarizes the methods that were investigated and demonstrates the wide range of techniques investigated in the area of energy efficiency in additive manufacturing.

4.4. Industries Addressed in the Studies

The industries that were covered in each research paper were taken into account in our examination of the selected articles. Seventy publications (42.7%), a sizable chunk of the research, omitted the industry. The industries in the selected papers were the metal industry at 11.6% (19 papers), aerospace at 7.9% (13 papers), semiconductors at 5.5% (9 papers), automotive at 4.3% (7 papers), and machine tool industry at 3.7% (6 papers). A smaller percentage of the studies were focused on industries such as chemicals (2.4%, four articles), composites (1.2%, two papers), and several other fields (each represented in 1–2 publications). These results highlight how many different sectors are investigating energy efficiency in additive manufacturing. Figure 4 presents a summary of the distribution of publications according to the industries they addressed. Moreover, our analysis showed that a number of other industries, such as medical, nuclear, magnetic refrigeration, construction, electric motors, ceramics, jewelry, composite manufacturing, water collection and transportation, battery, foundry, optical, energy harvesting, power, precision irrigation, energy, robotics and automation, and hydraulic systems, were also mentioned in the literature. This demonstrates, even more, how widely used and relevant energy efficiency is in additive manufacturing across several industries.

4.5. Scale of AM Usage

In addition, we assessed the scale at which additive manufacturing (AM) was applied in each investigation in our analysis of the chosen papers. We discovered that 115 publications, or 70.1% of the studies, concentrated on AM utilization at the laboratory size. Prototyping was the subject of 14.6% (24 articles) of the studies, while industrial-scale applications made up 11.6% (19 papers) of the studies. Only four studies, or 2.4% of the total, omitted mentioning the frequency of AM usage. These results show that, despite the existing corpus of research being dominated by laboratory-scale investigations, interest in industrial and prototype uses of AM in the context of energy efficiency is expanding. Figure 5 presents a summary of the distribution of publications based on the degree of AM usage.

4.6. Materials Used

The most typical materials used in additive manufacturing were also evaluated in our analysis of the chosen articles. We discovered that 48 out of the study publications, or 29.3%, failed to list the materials utilized. Titanium was mentioned in 13.4% of the studies (22 papers), polymer in 12.2% of the studies (20 papers), stainless steel in 8.5% of the studies (14 papers), aluminum in 6.1% of the studies (10 papers), composites in 6.1% of the studies (10 papers), and steel in 5.5% of the studies, as the most frequently mentioned materials. A few less frequent materials were nickel-based alloys (2.4%, four studies), copper (1.8%, three papers), magnesium, Inconel, concrete, biodegradable polyesters, and ceramic (each represented in 1.2%, two publications). Twelve articles (7.3%) of our selected sample cited other materials. These findings highlight the many materials employed in additive manufacturing, as well as their different prevalence in current research. Figure 6 summarizes the distribution of publications based on the mostoften utilized materials.

4.7. Overview of the Timing of Quality Inspection in the Selected Publications

We examined the timing of each study’s inspection of quality in our analysis of the selected publications. We noticed that 59.8% (98 articles) of the research did not carry out quality inspection. In contrast, 29 articles, or 17.7% of the investigations, included quality checks that were done after printing. Sixteen articles (9.8%) studies did not include information on when the quality inspections should be conducted. Only 3.0% (five articles) of the research used in-process quality inspection. These results show that although quality inspection is an essential component of additive manufacturing, it is not consistently covered in the corpus of literature currently available. Figure 7 presents a summary of the distribution of publications based on the timing of quality inspection [201].

4.8. Whether Energy Consumption Is Studied

Our examination of the selected papers also looked into whether each one examined energy consumption. In our analysis, we discovered that 101 studies, or 61.6% of the total, explicitly addressed energy use, while 43 papers, or 26.2%, did not. Seventeen papers (10.4%) evaluated or analyzed energy use in some detail. Only 1.8% (3 papers) of the publications lacked a statement on whether or not energy usage was researched. These results highlight how crucial it is to focus on energy usage when discussing energy efficiency in additive manufacturing. Figure 8 summarizes the distribution of publications based on the investigation of energy use, and sheds light on the degree to which this issue is taken into account in the existing body of knowledge.

4.9. Whether Energy Optimization Methods Were Used

In addition, we evaluated each study’s use of energy optimization in our analysis of the chosen articles. We discovered that 45.7% of the studies (75 publications) did not use energy optimization, whereas 38.4% (63 papers) did. Twenty-four publications, or 14.6% of the studies, discussed or partially implemented energy optimization. These results indicate that although energy optimization is an important part of energy efficiency in additive manufacturing, there is still room for improvement and more focus in this field. Figure 9 illustrates the distribution of articles based on the use of energy optimization, and reveals the extent to which this subject is now covered in the body of knowledge.

4.10. Is the Correlation between Energy Consumption and Quality Studied?

An analysis of the selected articles reveals that 82.9% of the studies (136 in total) did not explore the connection between energy use and quality in AM. However, 13.4% of the studies (22 in total) did investigate this relationship, with a further 3.7% (6 studies) partially discussing it. Despite the majority of research not focusing on this link, the interest in understanding it within the context of energy efficiency in AM is significant, as demonstrated by the 17.1% of studies that did consider this relationship (Figure 10). Figure 10 provides a summary of the distribution of the publications based on the investigation of the relationship between energy use and quality.

4.11. Overview of the Extent to Which Printing Time Optimization Is Addressed in the Selected Publications

The investigation further reveals that 79.9% of the studies (131 in total) did not delve into printing time optimization. However, 15.2% of the studies (25 in total) did explore this area, with a further 4.9% (eight studies) partially discussing it. Even though most current research does not emphasize printing time optimization, there is a notable interest in understanding its correlation with energy efficiency in AM, as indicated by the 20.1% of studies that did consider this aspect (Figure 11). Figure 11 displays the distribution of publications based on whether printing time improvement was researched.

4.12. Sustainability Consideration

In our review of the selected papers, we also assessed whether each study addressed the aspect of sustainability. We found that a substantial 57.3% (94 publications) of the studies did not include discussions on sustainability. However, 23.2% of studies (38 in total) did touch upon or partially explore sustainability, while 19.5% (32 studies) did not state whether sustainability was considered. Despite most current research not placing a strong emphasis on sustainability, there is a significant interest in understanding its correlation with energy efficiency in AM, as indicated by the 42.7% of studies that did consider sustainability (Figure 12). Figure 12 summarizes the distribution of publications based on whether sustainability was taken into account.

5. Discussion

5.1. Approaches to Achieving Energy Efficiency in Additive Manufacturing

Our investigation identified several strategies for additive manufacturing energy efficiency. A few of these are:

• Using AM instead of conventional manufacturing techniques.
• Cutting cycle durations and maximizing laser power by using specialized materials or substitute materials for a greater energy absorption.
• Implementing topology optimization methods to achieve lightweight design and superior mechanical performance. This approach not only saves materials, but also enhances energy efficiency. Works, such as those [202] on the constant–force compliant finger, and [203] lightweight robotic gripper, underscore the relevance of topology optimization.
• Making use of a variety of modeling tools, including design of experiments, CFD simulations, Pareto surfaces, and mathematical models.
• Calculating the energy lost to powder particles beneath the laser using discrete event simulations.
• Conducting life cycle analyses.
• Adopting more effective AM techniques, such as wire + arc additive manufacturing (WAAM) and improved printing techniques.

There is still considerable space for improvement, since many studies fail to explicitly address the benefits of using AM over more conventional techniques or the requirement for post-processing.

5.2. Correlation between Energy Consumption and Quality

According to our study, several studies touched on the relationship between energy use and additive manufacturing quality. For instance, a research article noted that 31% of all energy is used for quality assurance, which is sometimes necessary and requires energy. Further studies indicate that, under certain conditions, higher power levels combined with minimal vibrations can improve part quality. This, when optimized, may reduce the overall process time and potentially the total energy consumption. Furthermore, the particle size used in AM processes can influence both energy consumption and the quality of the final product. Typically, smaller particles can allow for a higher resolution and an improved surface finish, but may require more energy for sintering or melting. Conversely, larger particles might reduce energy consumption, but could compromise the detail and finish of the produced parts. Thus, it highlights the need for further research to fully understand the complex relationship between energy use, particle size, and output quality in AM processes.

5.3. Justification for Using AM over Traditional Manufacturing Methods

Only a few studies, according to our research, explained why AM was chosen over conventional manufacturing techniques. In several investigations, hybrid manufacturing methods that integrated additive and subtractive manufacturing techniques were established. The benefits of employing AM over conventional approaches and the consequences for energy efficiency of such decisions require further study.

5.4. Material Reuse in Additive Manufacturing

The possibility for material reuse in additive manufacturing methods is another area that needs more study. According to our study, the present literature does not adequately cover this subject. Further research is necessary because the publications do not consistently claim that post-processing is required to finish the portions.

5.5. Sustainability Considerations

Surprisingly, our study showed that just a handful of the assessed studies studied or discussed sustainability in full, while none of them thoroughly explored it. This shows that there is a large research gap in understanding how energy efficiency and sustainability relate to additive manufacturing. Future studies have to concentrate on bridging this gap by looking into sustainable methods and incorporating them into AM procedures.

5.6. Scale of AM Usage

The use of AM in research ranged in scope, with a bulk of them concentrating on laboratory settings. This suggests that further investigation is required to assess the energy efficiency of AM techniques in commercial and prototype applications. Examining these various settings will help us gain a more complete knowledge of how much energy is used in additive manufacturing.

5.7. Quality Inspection in Additive Manufacturing

Our investigation revealed that there are several methods for quality inspection in additive manufacturing, although many studies omitted a procedure for quality inspection. This disregard for quality inspection prompts questions regarding the dependability and consistency of the components created for these research studies. The creation and incorporation of efficient quality inspection techniques into AM processes, as well as any possible effects they may have on energy usage, should be the main areas of future study. Investigating in-process quality inspection methods might be very helpful since they might make it possible to see problems and take action before they result in component failure or further energy loss [204].

5.8. Optimizing Printing Time in Additive Manufacturing

A lack of studies that addressed printing time optimization suggests that additional study is needed in this field. In AM processes, printing time optimization may have a direct impact on energy usage and overall effectiveness. Future research should look into several strategies for speeding up printing, such as streamlining the design process, putting in place cutting-edge algorithms, or employing more effective technology. For additive manufacturing processes to be more effective, it will be crucial to comprehend the connection between printing time optimization and energy usage.

5.9. Material Reusability in Additive Manufacturing

The studies that were assessed did not go into great detail on the subject of material reuse. Reusable materials are essential to sustainable production because they help reduce waste and the process’ overall environmental effect. Future studies should examine the possibility of material reuse in various AM techniques and how it can affect energy usage. Additionally, research should look at the creation of novel recycling strategies and material recovery systems that enable effective and sustainable material management in AM.

5.10. Post-Processing in Additive Manufacturing

Current literature does not uniformly highlight the significance of post-processing in attaining final product specifications in additive manufacturing, indicating the need for further investigation. Post-processing techniques such as support removal, heat treatment, and surface finishing can considerably impact the entire energy consumption and manufacturing process efficiency. A deeper understanding of the energy needs and optimization techniques for post-processing in AM is necessary. Future studies should evaluate the energy implications of various post-processing processes and develop strategies to reduce their energy usage while retaining the target part quality.

5.11. Machine Consumables and Maintenance

The entire energy consumption and effectiveness of AM processes are significantly influenced by machine consumables and maintenance [205]. However, the extant research does not go into great detail on these aspects. The energy implications of routine maintenance and calibration should also be investigated, as well as the energy usage of machine consumables such print heads, nozzles, and build plates. The reduction in energy consumption in AM might be considerably aided by the identification of energy-efficient consumables and maintenance techniques [205].

5.12. Industry-Specific Applications and Challenges

Although the examined literature covers a wide range of sectors, there is still a need for a deeper investigation of the applications and difficulties linked to energy efficiency in additive manufacturing that are industry-specific. Understanding the distinctive energy consumption patterns and optimization prospects in many industries, such as aerospace, automotive, and medical, should be the main objective of future study. Further investigation is also required to examine the possible advantages and restrictions of AM adoption in sectors that have not yet adopted this technology broadly, as well as the creation of specialized energy-efficient solutions for these industries.

5.13. Groundbreaking Research and Innovative Ideas in Additive Manufacturing

The current state of the literature at the moment does not comprehensively cover ground-breaking studies and cutting-edge concepts that could change energy efficiency in additive manufacturing. Future studies should concentrate on investigating cutting-edge techniques, products, and technologies that have the potential to dramatically increase energy efficiency and lessen the environmental effect of AM. Investigating the possibilities of cutting-edge machine learning algorithms for optimizing process parameters, looking into the utilization of renewable energy sources to power AM equipment, or creating novel materials with improved energy-absorbing qualities are a few examples of what this may entail.

5.14. Cross-Disciplinary Approaches and Collaborations

In the variety of research currently available, the potential for interdisciplinary methods and cooperation in additive manufacturing has not been fully analyzed. Bringing together knowledge and experience from several disciplines, such as material science, computer science, and engineering, may result in creative answers for enhancing AM energy efficiency. Future study should concentrate on encouraging partnerships between academics and business experts from diverse industries to collectively address issues with additive manufacturinga energy efficiency. This may result in the creation of innovative technologies and comprehensive optimization methodologies that take into account a variety of AM-related factors, including material qualities, process variables, and post-processing methods.

5.15. Exploring the Potential of Digital Twins in Additive Manufacturing

Digital Twins, as virtual replicas of physical systems, have the significant potential to enhance energy efficiency in additive manufacturing. They allow for the real-time simulation and analysis of the manufacturing process, enabling the identification and mitigation of potential inefficiencies prior to physical production. This capability reduces waste and errors, optimizes energy-consuming steps, and assists in designing parts in a more energy-efficient manner [206]. Despite being in the early stages of implementation, the integration of Digital Twins in additive manufacturing represents a promising path for improving energy efficiency and striving toward a zero-defect production process [207].

The existing body of research on energy efficiency in additive manufacturing has advanced significantly, but there are still a lot of areas that need more study. The future development of energy-efficient additive manufacturing will depend on gaining a deeper knowledge of the variables affecting energy consumption in AM processes, as well as investigating the possibility for sustainable practices and material reuse.

6. Framework for Energy Efficiency in Additive Manufacturing

Achieving energy efficiency in AM is a complex, multifaceted problem that is not well-depicted in the literature. Most research works focus on isolated solutions for specific cases, rather than studying energy efficiency holistically. This section identifies all factors involved in the AM process that directly or indirectly affect energy efficiency. To ensure energy-efficient and sustainable manufacturing using AM, a holistic approach is needed to study the entire life cycle of the AM process [208]. Furthermore, the correlation between energy efficiency and product quality is almost absent from the literature. In the contemporary manufacturing landscape where sustainability is the primary goal, achieving desired quality parts with an energy-efficient AM process is vital for competitiveness [199]. Additionally, most papers lack a clear explanation of why AM is used compared to conventional machine use, requiring proper justification to assure the most efficient manufacturing method is selected.

With these considerations in mind, we developed the holistic framework illustrated in Figure 13, presenting the AM stages that affect energy efficiency and sustainability. Our framework identifies key factors affecting energy efficiency in AM, including product design, material type and form, energy requirements for manufacturing AM materials, slicing, AM process, post-process treatment, and the reuse of AM materials [209]. To make AM more energy-efficient, strategies that lower the amount of energy used throughout the whole process must be employed, such as optimizing design, using energy-efficient machines, selecting energy-saving materials, and optimizing the printing process.

The primary factor affecting the energy efficiency of AM is the design of the product. Therefore, it is crucial to document all design aspects that could impact energy efficiency. The most energy-efficient design should be chosen considering other mechanical and functional requirements. The type and form of material constitute the second aspect affecting energy efficiency. Materials used in AM should be developed with a focus on energy efficiency, considering attributes such as high energy/heat absorption or other energy forms required for material transformation. A largely under-researched area is the energy required to manufacture the AM materials and shape them to their required form.

The slicing of the part indirectly affects energy efficiency, as it determines the paths that the AM nozzle will follow. However, besides energy efficiency, the chosen paths and their sequence also impact the mechanical properties of the part. Therefore, it is essential to address all these aspects simultaneously, as they might conflict with one another. For instance, improving energy efficiency could lead to a decrease in mechanical properties and vice versa. The subsequent step involves the actual AM process, where highly energy-efficient equipment is necessary to minimize energy consumption [210]. Moreover, enhancing the capabilities of AM machines can reduce the required printing time, thereby decreasing the energy needed for the entire process. AM is well known for the imperfection in terms of surface quality and high-precision dimensions. As such, a significant proportion of AM parts require post-processing treatment, and the energy expended during these stages should also be accounted for in the total energy calculation for the entire process. Additionally, the reuse of AM materials, particularly in powder-based AM methods, is crucial for the process’s sustainability. Consequently, the total energy required for AM is the aggregate of the energy consumed at each of these stages.

This holistic framework emphasizes the importance of considering all stages of the AM process and their interactions to achieve optimal energy efficiency. By addressing each factor and understanding their interconnected nature, it is possible to develop more effective strategies for reducing energy consumption in AM processes. For future research, it is crucial to explore the relationship between energy efficiency and product quality further. This would allow for manufacturers to strike a balance between creating high-quality products and using energy-efficient processes, ultimately contributing to a more competitive and sustainable manufacturing landscape. Moreover, there is a need for more in-depth studies to compare AM with conventional machining methods in terms of energy efficiency. By providing clear justifications for the selection of manufacturing methods, researchers and manufacturers can make informed decisions and contribute to the overall goal of sustainable manufacturing.

Additive manufacturing (AM) can be made more energy-efficient by employing strategies that reduce the amount of energy used throughout the entire process. Here are some ways that AM can consume less energy:

• Optimize the design: One of the best ways to reduce energy consumption in AM is by optimizing the design [210]. Minimizing material and energy usage during creation is essential. The optimization should consider the printing method, layer thickness, and the necessity of support structures.
• Use energy-efficient machines: Another way to save energy in AM is to utilize energy-efficient machines. Newer AM machines consume less energy than older models, so using them can significantly decrease energy usage.
• Use energy-saving materials: The materials used can have an impact on the energy efficiency of AM. Materials that need less energy to generate, such as bio-based polymers or recycled materials, can help minimize the amount of energy required to develop the materials.
• Improve the printing process: Improving the printing process can also result in lower energy use. This may be accomplished by slowing down the printing process, maintaining an appropriate temperature, and minimizing the need for support structures.

Our holistic framework for energy efficiency in additive manufacturing highlights the importance of considering all factors and their interactions throughout the AM process. This comprehensive approach paves the way for future research and practical applications, ultimately promoting a more energy-efficient and sustainable manufacturing industry. The framework we presented in this section holds significant value for both research and practical applications. For researchers, this framework can serve as a roadmap to identify the gaps and opportunities in the field of energy-efficient additive manufacturing, thus guiding future studies. Additionally, it can help in structuring and organizing research findings in a more coherent and comprehensive manner. For practitioners, this framework can provide a systematic approach to evaluate and improve energy efficiency in additive manufacturing processes. By following the framework, practitioners can pinpoint areas of inefficiency, develop strategies for optimization, and monitor the impact of these strategies over time. Furthermore, this framework can support decision-making processes, as it provides a holistic view of the factors influencing energy efficiency in additive manufacturing, aiding in the selection of the most energy-efficient methods and technologies.

7. Conclusions

Our comprehensive analysis of the literature on energy efficiency in additive manufacturing (AM) provides an extensive understanding of the current state of research, while simultaneously identifying the key areas requiring further investigation. One prominent gap highlighted in our review is the lack of standardization in the measurement and reporting of energy consumption in AM processes. This gap obstructs the effective evaluation and comparison of different AM systems, thereby hampering efforts to identify potential areas for improvement. The development of standardized methodologies to accurately measure and document energy usage in AM processes is, therefore, a pressing need in the field.

In addition to standardization, our review underscored the lack of comprehensive understanding concerning the complex interactions among various parameters influencing energy consumption in AM. This knowledge gap poses a significant challenge for optimizing energy efficiency in AM processes. Because of the complexities of these processes, more focused and systematic study is needed to untangle these connections and find ways for enhancing energy efficiency. Increasing our grasp of these intricacies will not only improve the efficiency of AM operations, but also provide a better platform for future innovation and growth.

Our analysis also provided further insights and light on the possibility of modern control systems to increase energy efficiency in AM. These sophisticated technologies have emerged as a possible option for energy optimization by providing real-time monitoring and change of process parameters. The potential of these systems highlights the need for increasing investment in their development and deployment, as well as thorough study, in order to realize their potential advantages.

The incorporation of renewable energy sources in AM systems is another aspect that our review highlighted. Renewable energy can not only reduce the overall energy consumption, but also enhance the sustainability of AM systems. Aligning with recent studies, our review demonstrates that renewable energy sources can significantly enhance energy efficiency, as opposed to fossil fuels, which have been shown to negatively impact energy efficiency [4].

Alongside renewable energy, our review emphasized the crucial role of robust energy management strategies within AM systems. Implementing measures such as turning off equipment when not in use and enforcing energy-efficient practices can significantly reduce energy consumption and costs. The strategic management of energy should be regarded as an integral part of optimizing AM processes.

Beyond these key findings, our review underscored the intricate relationship between energy consumption and the quality of AM products, an area requiring further research. Factors such as power levels, vibrations, and particle size simultaneously affect energy usage and the quality of the products, warranting more extensive exploration.

Several other areas requiring further investigation were also identified, including the justification for using AM over conventional manufacturing methods, the potential for material reuse in AM, sustainability considerations, the application of AM techniques in commercial settings, industry-specific applications and challenges, and the potential for interdisciplinary approaches and collaborations in AM. These areas have a lot of potential for improving our understanding of energy efficiency in AM, opening the path for more sustainable and efficient methods.

To summarize, while substantial progress has been achieved in the literature on energy efficiency in AM, there are still many areas that require further research and deeper investigation. The future development of energy-efficient AM will hinge heavily on gaining a deeper understanding of the variables affecting energy consumption in AM processes, and exploring the potential for sustainable practices and material reuse. By providing a comprehensive and current overview of the state of research on energy efficiency in AM, our review underscores the critical areas where standardization, research, and implementation are required to optimize energy efficiency in AM.