Additive manufacturing (AM) has rapidly evolved since its inception, and investment in AM technology has flourished in both the public and private sectors. This article, the first of two parts, evaluates predictions made in FORGE in 2012 and illustrates some appropriate applications that could affect (or already have affected) forging processes and markets.
Drawing from the notion of time travel from the 1985 movie Back to the Future, this article explores the accuracy of predictions made in my article “Will Additive Manufacturing Threaten the Forging Industry?” from the August 2012 issue of FORGE. In 2020, Editor Dean Peters and I discussed the idea of revisiting the predictions of that article and offering some analysis of the results.
Without a flux capacitor, which enabled time travel in the DeLorean time machine used in Back to the Future, we selected five of the 13 original predictions most relevant to the forging industry. Table 1 captures the 2012 predictions and updates their status in 2020. The five Past Points selected for revisiting are underlined in the table. Reviewing these Past Points, we reflected primarily on the Present and, like any movie trilogy, foreshadow the future.
AM will not Compete with Large Rings or Open-Die Forgings
Bulk processing of open-die forgings and ring rolling will be more economical than AM. Simple economics dictate that AM will not compete with large, open-die forgings weighing tons. First, AM machines are limited by size and build rates. Their working envelopes are physically limited. Second, it does not make sense to build large-tonnage parts from relatively costly powder or wire feedstock. In other words, to invest in creating fine powder or wire (the time and energy for which add to processing costs) and then reconsolidate the same into a large part weighing tons does not make economic sense.
Innovations are rapidly unfolding, however, such as with Sciaky’s Electron Beam Additive Manufacturing (EBAM®) and DM3D’s bulk-powder laser-deposition processes, which are making inroads into large-part fabrication. Following the money, high-value alloys – titanium, nickel and highly alloyed steels – are the best candidate materials. “Large” depends on AM machine processing chamber size and, interestingly, AM chamber atmospheres that lead us to innovations in ring rolling, which we will touch on in a few paragraphs.
Chicago-based Sciaky has printed large parts within the envelope of 19 feet x 4 feet x 4 feet and circular parts measuring 8 feet in diameter. Consistent with the predictions of the past, Sciaky offers a variety of expensive alloys such as titanium, Inconel, tantalum, tungsten, niobium and stainless steel. If wire feedstock is available for an alloy, however, any part could theoretically be fabricated with build rates ranging from 7 to 20 pounds/hour.
Even more exciting is the concept of designing components with an “alloy gradient” to tailor part properties and performance through alloy selection, which varies from one end of a part to the other. Theoretically, with the combination of alloy gradients and higher build rates, Sciaky could make functionally graded forging dies via wire feedstock.
Despite the efficiencies of wire feedstock, rapid deposition rates such as DM3D’s Direct Metal Deposition approach keeps powder in the competitive large part, AM fray. Readers are reminded of FORGE’s February 2019 issue, which featured “DMD Additive Manufacturing on Forging Dies.” Following up that article, Dr. Bhaskar Dutta of DM3D indicated the company is focusing on printing large parts up to 10 feet.
To date, DM3D has printed 5-foot parts weighing up to 800 pounds, which is impressive for a powder-deposition process. Dr. Dutta indicated that these printed parts are replacements for castings and forgings, which suggests my 2012 prediction is partly false! AM is now competing with large forgings, but the questions now are: What is the definition of large either in terms of dimensions or weight? Are large AM parts pre-dispositioned by alloy and AM process? Is size an issue at all?
DM3D printed a half-scale nozzle liner for the RS25 engine for NASA’s Marshall Space Flight Center.
This part, measuring 45 inches in diameter at the base and 52 inches tall and weighing 400 pounds, illustrates the increasing capability of AM to produce large components (courtesy DM3D).
In the 2012 article, we cited AM rings with AM features negating the need to oversize the rolling of a ring before machining a feature by removing excess material to create a lug or attachment point. Now, with the large-scale open-atmosphere MELD process (formerly known as Additive Friction Stir, an additive variation of friction stir welding) in air, rings can be produced via another variant of AM.
Finished machined rings fabricated by the MELD process. The as-printed rings are of 6061 aluminum.
The small ring is 5 feet in diameter; the larger is 10 feet in diameter.
MELD machines employ a solid-state process technology to produce rings and other geometries.
MELD Manufacturing Corporation of Christiansburg, Va., has demonstrated their solid-state process technology to produce rings (and other geometries) of nearly unlimited size in many different materials, including steel, aluminum (2xxx, 5xxx, 6xxx, 7xxx), copper and titanium. Since MELD is a solid-state process, it yields dense products without porosity, hot cracking and little residual stress. Typical build rates for the MELD process (pounds per hour) are 1.5 for nickel alloys, 5.5 for titanium alloys, 10.7 for steel alloys and 20.0 for aluminum alloys. In certain applications, the deposition rate can exceed 30 pounds per hour. The MELD process utilizes bar feedstock, which offers significant cost savings over wire or powder-based AM processes.
While exploring AM in ring manufacturing, Schatz Bearing of Poughkeepsie, N.Y., surfaced. The company is embracing AM to address geometrical challenges presented through conventional manufacturing methods, namely machining. Complex geometries associated with the outside of a bearing are labor-intensive, which results in higher manufacturing costs. The company is applying AM to bearings with complex geometries and extending AM concepts to next-level parts and assemblies (e.g., gears, shafts, housings, etc.). This extension of AM to matched components multiplies the value of AM within a bearing system, further providing value to the customer.
Schatz Bearing leverages AM capabilities to provide enabling geometry not afforded by wrought and machined products. Immediate AM value is exploited in mounting features such as flanges with mounting holes; notches, tabs and grooves to orient and mount bearings; and integrated locking features or preloaded features. Other benefits are being accrued through layered alloys to manage thermal gradients, resist corrosion and resist fatigue, all of which contribute to superior performance. Ultimately Schatz’s customers will derive value from their exploitation of AM in its line of bearings for aerospace, medical and industrial applications.
Bearing rings produced by AM for Schatz Bearing.
Looking into the future toward the next issue of FORGE, we will examine the predictions regarding AM prototyping and forging, AM short-run production and forging, and die repair. We will explore how these industries will have to compete and complement each other by delivering value in the future. Until then, please travel through time safely.