Additive manufacturing techniques are no longer in their infancy. They are quickly emerging into serious options for the production of metallic parts. Forge shops should keep a watchful eye on this unfolding technology, both as a competitor and as an opportunity.
"Check six” is aviation slang for watching for an attack from one’s 6 o’clock position or aft quarter. In the dog-fighting world of manufacturing, forges are constantly pestered or even attacked outright by competitive forces – casting, high-speed machining and, now, additive manufacturing. This article is intended to illuminate the threat of additive manufacturing, which might be closing in on the forging industry.
Additive manufacturing is one of those technologies that impression die forges especially need to watch. It is not the intent of this article to go deeply into the various additive manufacturing processes but rather to alert the forging community that various processes are rapidly being developed and deployed, some of which are directly relevant to forge shops.
Additive manufacturing (AM) is a disruptive technology that has evolved during the past 30 years from the creation of plastic parts via myriad rapid prototyping technologies to metal part creation via several new and evolving metal-deposition technologies. AM is essentially the layer-by-layer fabrication of components without tooling or fixtures. Examples of AM processes include powder-flow methods or powder-bed methods.
In the case of powder flow, metal powder is deposited and simultaneously fused, typically with a laser. Optomec’s LENS system exemplifies this process (Figure 1). With powder-bed methods, particle fusion occurs by the rastering of a laser or electron beam across a flat bed of metal powder (Figure 2). Other processes are being developed and deployed in the marketplace with varying strengths and weaknesses. Common to all of these processes is the notion that a part is made incrementally, layer-by-layer with fusion of discrete metal particles to form a unique part. AM is an exciting technology that enables “one-off production,” prototyping or short-run production of metal-component manufacturing without the upfront cost of forging dies. Table 1 identifies some of the metallic AM technologies with respect to their origin, trade name, energy source, feedstock and alloys.
Benefits of Additive Manufacturing
Multiple benefits of AM have been identified within this growing industry. One-off or short-run parts are possible without tooling. Lead times are reduced drastically. Input alloy requirements and processing energy requirements are considerably lower than forging process requirements. These benefits equate to competitive advantages for AM over forging. Geometries heretofore not possible via conventional manufacturing technologies are now possible. This is not necessarily a threat to the forging industry.
Challenges of Additive Manufacturing
Like any evolving technology, developers of AM have to overcome many technical and financial challenges. Table 2 shows teh technical challenges and potential solutions.
There are multiple financial and economic challenges facing AM processes. Depending on one's perspective, costs are associated with capital equipment, powder processing, part processing or building costs, finishing costs, inspection costs, etc. North Carolina State University and presumably others are analyzing and modeling the costs of AM. Table 3 lists some of the financial challenges facing AM.
Despite the costs of AM, a compelling statement could be made that the cost of additive manufacturing a metallic part is quite small when compared to the cost of an aging system it could be used on, such as aging military systems that are critical to defense. For new systems, the cost is relatively low compared to the opportunity gained by rapid entry into a market with a new product. Time is money.
With worldwide enthusiasm for AM, these challenges are being addressed summarily. The American Society for Testing and Materials (ASTM) has created an International Committee for AM. The subcommittees are addressing issues of Test Methods, (F42.01), Processes (F42.02), Materials (F42.03), Design (F42.04) and Terminology (F42.90). Eventually, another major step in the maturation of this new industry is when specifications are created for AM, resulting in the ultimate development and tabulation of design allowables in Metallic Materials Properties Development and Standardization (MMPDS).
Additive Manufacturing Looks Forward
In 2009, a Roadmap for Additive Manufacturing was published by the University of Texas, Austin. The roadmap identified industries that would benefit from AM; listed technology goals and barriers; explored design and analysis; discussed processes and machines; identified materials and materials processing; discussed energy and sustainability; and offered recommendations.
Within this roadmpa, forging is cited five times. The first reference suggests that AM is sometimes economically competitive with aerospace forging and machining. The second reference suggested that: "Within the next 10-15 years, AM should become an integral component of available manufacturing processes for metallic parts, now represented primarily by forging, casting and machining." This reference identified the value of AM in reducing the buy-to-fly ratio of forgings primarily through the reduction of input weight to the component. The third reference addressed the limited number of powders available for AM. Although many powders are available, many forged alloys are not replicated with available comparable powders, ribbon or wire. In other words, one cannot simply replace a forged alloy with AM alloy since the same chemistry is not available in the feedstock forms required of different AM processes. The fourth reference explored the need for consistent quality feedstock for AM, not unlike the consistent quality produced by modern alloy suppliers. The fifth and last reference to AM an dforging again focused on aerospace forgings. In this reference, the roadmap suggested targeting secondary or noncritical structures as a first step. With a roadmap in hand, the Am industry has a plan to move forward.
Running parallel to the AM Roadmap, an Additive Manufacturing Consortium has been organized by the Edison Welding Institute in Columbus, Ohio. This group is comprised of industrial, government and academic partners to develop and deploy AM techniques inclusive from Manufacturing Readiness Level (MRL) 3 through Level 7. MRLs are used within federal development circles to assess the maturity of manufacturing technology. Low MRLs reflect basic research in the maturation phase. This leaves the basic research (MRLs 1-3) to research and development organizations such as Small Business Innovative Research firms and universities and the incremental improvements (MRLs 8-10) to implementing organizations such as OEMs. Other additive manufacturing consortia or collaborations are forming around the world with the same overarchign objective of developing and deploying AM technology. These organizations are potential partners for forges to explore opportunities between AM and the forging industry.
In the very near term, investment in AM will continue to increase. At the time this article was written, the U.S. government launched the National Networked Manufacturing Initiative. The first investment will be to focus on AM with a $45 million contract award, which is expected to occur before the November elections. Investments will continue by the U.S. Departments of Defense and Commerce, AM machine manufacturers, AM service bureaus and OEMs. Universities are involved with an array of AM machines and research topics. Research is active in Canada, Europe, South Africa and, presumably, India and China. Wherever modern manufacturing and prototyping is occurring, it is safe to assume that AM is present.
In light of this global excitement and investment in AM, I have formulated the following predictions:
- R&D funding will be channeled into AM, leaving less funding for conventional manufacturing-technology research. Perhaps some of the basic metallurgical research could be applied to conventional forming processes, especially in the area of microstructural modeling and component performance prediction.
- AM will evolve rapidly for three reasons. First, between the Internet, “professional vs. social networking” and the advent of “digital threads,” everything happens more quickly. Second, the people driving the development of these technologies are challenging the linear development paradigms of the past. They just think and operate differently, for better or for worse! Third, the market is pulling on rapid design and manufacture of short-run parts for prototypes, applications or outright small orders.
- AM will thrive in complex shapes, with expensive alloys, in relatively small part volumes and in noncritical applications.
- AM enables distributed manufacturing around the globe. A solid model could be e-mailed to an AM machine anywhere in the world to produce a part. This assumes the machine is ready and secondary finishing and inspection operations are available or perhaps even required.
- AM will not compete with large open die or ring rolling. Bulk processing of open-die forgings and ring rolling will be more economical than additive manufacturing.
- Ring rollers might exploit additive manufacturing to add discrete features on rings (Figure 4). Ring rollers and part designers are advised to monitor AM for advances to achieve this capability.
- AM will eventually compete with forgings in short-run production of both new parts and replacement parts for legacy systems. Program managers of new systems have always needed parts now with zero or minimal tooling costs. Supply-chain managers of legacy parts are reluctant to invest in tooling for short-run production, especially when tooling can be obviated by AM.
- AM will spawn other unpredicted innovations. Several years ago, our program invested in what became ProMetal. We did build the knowledge base of 3-D printing of forging dies, but that domain was not necessarily the optimal implementation route for that technology. Instead, ProMetal pursued 3-D printing of casting molds with vigor, wiping out the need for patterns. Additionally, ProMetal integrated metal flow and solidification models into its offering, which is ideal for the foundry and the ultimate customer.
- AM could serve in tool repair, hard facing and the introduction of new, functionally gradient surfaces. By applying select materials to tool surfaces, one could theoretically tailor a forging die with variable frictional surfaces. In other words, one could tailor the coefficient of friction, or “mu.” Where resistance to flow is required, high-mu surfaces could be applied. Where less resistance to flow is required, low-mu coatings could be applied.
- AM could serve as a link between a prototype part and a forging. OEMs, Tier-1 and Tier-2 suppliers and designers are advised to identify and evaluate ways to integrate AM into the design and acquisition process.
- Subtractive processes (“machining” in the new lexicon of AM) will dominate parts of aluminum and alloys designed for machinability.
- AM will require a skilled but limited work force – skilled because the technology is cutting edge; limited because the machines do most of the work. Job growth will be in the areas of design for AM; AM research; AM system manufacture, installation, service and repair; and AM part finishing operations. These will probably be technically oriented positions requiring high levels of training.
- Designers will learn to design with anisotropic metals not unlike composite designers. Metal part designers already invoke anisotropy of wrought bar stock and plate. Clever designers will even specify build directions for applications, creating tailored properties.
Additive Manufacturing is not something to be reckoned with in the future. It is here now. So, keep “checking your six” to avoid becoming “a bogey” to AM. Perhaps you might even “fly in formation” with AM. Time will tell. I should be around the next five years. So, let’s see how this dogfight plays out!
This article was prepared under the Forging Advanced Systems and Technologies (FAST) Program sponsored by the Defense Logistics Agency, both at DLA Headquarters in Fort Belvoir, Va., and DLA R&D Contracting in Philadelphia, Pa.
Author Jon D. Tirpak is a frequent contributor to FORGE magazine, having most recently delivered the keynote address at FORGExpo 2011: An International Virtual Event. He is the executive director of FDMC and FAST program manager. He may be reached at 843-760-4346 or firstname.lastname@example.org
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