Metal Additive Manufacturing. Ehsan Toyserkani

to overhaul must be included in the analysis.

1.7 AM Trends, Challenges, and Opportunities

      With all the advantages that AM offers, even newcomers to the AM community appreciate the enormous potential and promise of technology that will transform the entire manufacturing enterprise in the next 10–15 years. Free complexity in designs, when industrial AM systems offer a platform to make them, is unfettered by the compromises of conventional manufacturing methods. With AM, designers do not design for manufacturing anymore; they design for end users. This is a paradigm shift.

      It is reported that AM would be able to lessen the capital needed to reach minimum low‐volume manufacturing [38]. This feature may lower hurdles for local manufacturing. In addition, the AM flexibility would facilitate the opportunity to produce a variety of products per unit of capital, reducing the changeovers and customization costs. To this extent, manufacturers are merging toward the understanding of different efficiencies AM can introduce throughout the supply chain, where there are four strategic paths to adopt AM for their businesses [38]:

      1 Value‐added proposition for existing products within traditional supply chains. In this case, companies would not radically change their products; however, they may explore AM technologies to help improve quality and reduce costs.

      2 Value‐added proposition by taking advantage of “economies of scale” offered by AM. In this case, companies would take the risk to transform the supply chain for their products.

      3 Value‐added proposition by taking advantage of “economies of scope” offered by AM. In this case, companies would be able to step into innovative personalized products and new levels of performance in their products.

      4 Value‐added proposition by pursuing new business models. In this case, companies will enjoy a new and effective supply chain for new business models with innovative workflow.

To follow any of the aforementioned strategies, companies need to put aside the traditional cost models and rubrics and adopt a holistic approach that will determine the impact of AM on their business. To critically assess the adoption of AM, Life Cycle Assessment (LCA) should be used. Such LCA sheds some light on the environmental and economic impact of a product or service to be offered to the market. The LCA evaluates all stages of the life cycle, from the extraction and development of raw materials, followed by AM processing, post‐processing, transportation, use, and end‐of‐life disposal. This is a major trend in the AM industry these days.

      In addition to new business models being developed by industry, there are several challenging factors that the AM community is addressing to overcome. In the following, these factors are discussed when emerging opportunities are elaborated.

       Qualified materials: One of the major challenges in the field of metals and metal alloys is the number of powders that have been qualified for use with metal AM systems, including laser, electron beam, and binder‐based AM processes. For example, there are currently more than 1000 steel alloys commercially available for conventional casting, but just a handful number has been verified for AM production by OEMs. In the case of aluminum alloys, the ratio is about 600:12. The shortage limits the number of parts that can be made and companies that can benefit from the technology. In addition, the relatively few qualified metal AM powders cost 5–10 times more than raw materials for casting, machining, and other traditional forms of manufacturing. Part of that problem is a lack of competition among suppliers. Another is low volume, with worldwide sales of metal AM materials totaling less than $400 million a year, a small fraction of the overall raw materials market. As the adoption of AM picks up steam, prices are expected to fall dramatically. As with most challenges, this one creates opportunities to improve powder production methods and, quite possibly, formulate entirely new powders to get the most out metal AM. For any material development, a holistic approach from material extraction to the end use and disposal must be considered.

       Speed and productivity: One of the challenges of AM processes is speed. In general, production throughput speed is low for mass production. Although AM makes it possible to consolidate parts, small working volume and post‐processing related to the surface enhancement add extra steps to the production time. Further process development is needed to enhance surface quality during AM processes to improve process productivity.

       To address these challenges and improve AM productivity, modular flexibility is being integrated into AM processes. The scalability and modularity supported by the proper selection of processes can help to achieve the quality and speed required. Companies are working on the development of a larger working envelope into which multiple heat sources (e.g. laser beams) are incorporated. Automation and intelligent software are being developed to coordinate all subsystems in harmony with a goal of productivity enhancement.

       Opportunities also exist in the field of computer modeling of AM processes to improve production via reliable and validated simulation rather than costly experimentation. Very few models have been developed to date, adding research and development costs to high material costs as deterrents for companies that might otherwise move into AM.

       Repeatability and quality assurance: Although the technology has already produced impressive results, it is also true that reliability and repeatability are still significant AM problems, particularly for mass production. Failure rates for many applications remain in a range where using the technology simply is not economically justifiable due to the number of failed parts and the need to post quality checking by an expensive setup such as CT. The underlying problem is that AM is so sensitive to both environmental and process disturbances, from fluctuating temperature and humidity levels to nonuniform powder sizes. Full control of the process and surrounding environment is virtually difficult, so the focus is on solutions that employ innovative sensors to monitor conditions and quality control algorithms to automatically adjust process parameters, such as laser power or process speed, to compensate for disturbances instead. Closed‐loop control is being incorporated into DED, and efforts are underway to add intermittent controllers to PBF processes due to their high speed. For PBF processes (e.g. LPBF), the major bottleneck to developing a closed‐loop control system is hardware speed and accuracy. The amount of data collected by sensors are high but still not at a high frequency of 200K Hz or more to be able to effectively tune process parameters. In summary, the more advanced hardware (sensors and computational systems), the closer to the closed‐loop control of PBF processes.

       Industry‐wide standards: Regardless of major advancements in AM over the last few years, the more nettlesome challenge is the lack of a comprehensive set of technical AM standards acceptable by industry. The absence of such standards may hinder the continued adoption of AM for industrial applications. Several main stakeholders have recognized the challenge and have started to take action. The American Society for Testing and Materials (ASTM), the American National Standards Institute (ANSI), International Standards Organization (ISO), and other standard organizations are working hard to develop standards platforms and procedures for AM. A road‐map assessment of the state of standards and standards gaps in AM has recently been published [39]. ASTM through its committee F42 is currently developing standards for metal AM processes, especially for LPBF. The developed standards have the potential to help industry to effectively assess the performance of AM systems as well as the quality of printed parts. Nevertheless, with all these efforts in place, many new and reliable standards are still required. This should also be noted that concrete standards should be published rather a partially developed standard that may include flaws. If the standards are retracted and revised due to flaws regularly, such retractions will undermine the industry thrust.

       End‐to‐end workflow, integration, and automation: In industry, anytime a new material/process/design or technology is used, a lengthy qualification process must take place. This testing is intended to prove (with lots of margin) that this new material/process/design or technology can meet all of the performance requirements. Many customers are reluctant to accept a new material/process/design or technology that does not have “heritage” in their applications. To minimize industry hesitation on the AM adoption, an effective end‐to‐end workflow must be developed that is simple but yet integrated and automated. All major industrial and nonindustrial