Читать книгу Metal Additive Manufacturing - Ehsan Toyserkani - Страница 28

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 AM systems providers are proposing ways to integrate their systems into complete end‐to‐end workflows. While AM is the core part of digital production, integration and automation of the end‐to‐end workflow are a different entity and beyond AM. However, any integration/automation must be well thought in harmony with AM limitations and features. The lack of digital infrastructure at the moment is a major obstacle to move with effective automated workflows for the AM industry. Automation basically begins with an effective streamline of part design and optimization through Design for AM (DfAM) tools, driven by digital warehouses and digital twins. Automated material supply lines for feedstock (e.g. powders) through manufacturing execution software should be developed to coordinate AM systems and workflow stations. Machine learning and artificial intelligence, as well as simulation, inline process monitoring software, and nondestructive testing (NDT), should work hand by hand to oversee the AM process to correct errors via when robots will remove and depowder parts from AM machines, followed by powder recycling and reuse. Automated post‐processing heat treatment, polishing, etc. should be fully integrated into the aforementioned workflow. Automated AM is a part of the factory of tomorrow, a forefront of the ongoing industrial revolution within the industry 4.0 approach.

 Software limitations: The commercially available software packages for the design of AM parts, support structure development, and interfacing with AM machines have limitations in assessing the feasibility of prints and identifying process constraints. In many cases, the ideas that are conceived and created in 3D modeling software exhibit major challenges to be printed mainly due to the issues with process constraints that are not included in the design. In addition, the current workflow software has limitations when it comes to AM to track individual items through each stage of the process to manage resources and delivery timelines. Another issue is associated with inter‐ and intra‐communication and collaboration that depends on the quality of information and transmission methods. The current software and hardware still need more improvements to facilitate timely communication in AM.

 Initial financial investments: One of the major barriers for metal AM adoption is a substantial investment needed to AM capital and ecosystem to deploy it to production. The AM ecosystem covers software, materials, experts, post‐processing equipment, certification as well as training for employees. This investment could be enormous hindering companies from embracing this technology effectively. One solution to this challenge is to rely mainly on AM service companies to integrate into the supply chain to derisk the AM adoption in the early stage. University and R&D centers can play an important role in providing fundamental R&D required as well as training platforms for companies that are trying to adopt AM but cannot invest in it significantly.

 Security: AM is fully integrated into the digital world; thus, its cyber–physical nature has raised major concerns. When AM has promoted globally distributed manufacturing, the existence of hackers is a reality. They can tweak the AM designs to create intentional defects that are not simply detectable but have catastrophic consequences while being used in actual systems. The vulnerabilities and large‐scale jobs conducted by commercial AM services may inherently be difficult to substantiate the quality of printed parts. The process and supply chains must firewall to address these security concerns. These measures could be the same as other manufacturing industries such as electronic printing; however, due to typical applications of AM‐made parts in critical applications such as jet engines, special validation procedures need to be developed to give assurance that the parts are not affected by the malicious attack in terms of intentional undetectable design alterations.

 Skillsets gap: AM experts' shortage is one of the main challenges in industry. Lack of understanding and expertise in AM is a critical factor in the AM adoption. There are a very limited workforce and highly qualified personnel to work and develop an entry strategy for new companies that want to embrace AM. A thorough understanding of AM capabilities prevents major misconceptions while introducing challenges correctly to decision‐makers. The knowledge gap at the moment is significant as companies have difficulties in developing effective and meaningful business cases for metal AM. Since AM needs a new design platform, mechanical engineers who have been trained to design for traditional manufacturing cannot effectively undertake design for AM. They will require a steep learning curve to master it. Their mindset must be changed through training and education. Overall, learning about the capabilities and limitations of metal AM will aid companies in developing meaningful and successful applications for the technology.

A few measures to address the current gap are to develop a degree level program at different universities and colleges. The program should include a holistic curriculum that covers a vast range of areas. Designing such curriculums is of great challenge. In addition, industry certification programs should be developed when each module of the programs is taught by experts from around the world. Promoting AM consultancies is another great way to foster knowledge transfer. In addition, AM conferences and webinars are playing critical roles to fill the skillsets gap.