Direct Metal on the Rise
Forget rapid prototyping, rapid tooling and rapid manufacturing, today's additive processes for metal alloys can do the impossible
By Todd Grimm
T.A. Grimm & Associates Inc.Edgewood, KY
Rapid prototyping, rapid tooling, and rapid manufacturing fall far short of describing the new breed of direct-metal technologies. While speed is inherent in the process and critical to the success, there is much more to the technologies that produce metal parts and tools through direct, additive processes.
Since the mid-1990s, companies have been working to advance rapid prototyping technologies for metal alloys, and their work is now paying off. Direct-metal technologies are no longer confined to R&D labs; they are viable and available today. Nearly a dozen companies offer direct-metal technologies, and progressive organizations are capitalizing on the benefits that result from doing what was previously impossible.
Yet the architects of these systems recognize that there are barriers to adoption, and most believe that it will be five years before technology becomes widely used. According to Adri Coppens, vice president of Accufusion Inc. (Ottawa, ON, Canada): “Our challenge is not in the technology, materials, or deliverables. It is finding early adopters and changing mindsets.”
Major corporations like Trumpf Group (Ditzingen, Germany), D-M-E (Madison Heights, MI), and MTS Systems (Eden Prairie, MN) have staked a claim in the market. These companies have invested in the development and commercialization of direct-metal systems. Interestingly, each has a different view of the primary application for direct metals. MTS’s subsidiary, AeroMet Corp. (Eden Prarie, MN) has focused on the production of complex parts in alloys that are difficult and costly to process. D-M-E’s MoldFusion division has targeted tooling inserts that reduce injection-molding cycle times. Trumpf-through its own systems, partnership with EOS, and a contract manufacturing agreement with POM-offers technologies for part manufacturing, short-run tooling, molds and dies for high volume, and mass production.
Tim Gornet, a CAE consultant at the University of Louisville (Louisville, KY), classifies direct-metal technologies in two categories, powder bed and powder deposition. With powder-bed technologies, a heat source or binding agent melts, sinters, or bonds powdered metal. Gornet states: “These technologies offer the advantage of self-supporting geometries and some offer fast build rates, but all of them are limited to processing a single alloy.” The powder-deposition technologies melt alloys and deposit them on a layer-by-layer basis. “The deposition systems have the unique capability to apply multiple materials to vary material performance characteristics,” Gornet says. “The limitation of these systems is that the deposition rate is somewhat slow, so most will use them to add material to a machined part or tool.”
One technology does not fit Gornet’s classification-Solidica Inc.’s (Ann Arbor, MI) ultrasonic consolidation (UC) combines additive and subtractive technologies in the same platform. Laying and welding (ultrasonically) alloy tape and machining excess material, UC is in a class of its own. Solidica may be a pioneer in what many believe will be the wave of hybrid machines that combine multiple processes.
Although there are many vendors and technologies, Dawn White, Solidica’s president, believes that each will find its place and over time, there will be many more companies and processes. “At IMTS, you can spend days and still not see all of the cutting, turning, and forming technologies,” White notes. “In the future, the same will be true of additive, direct-metal systems.” White believes that a success factor will be the collaboration of companies to discover and develop new applications and markets. The others agree. Each company stated that the direct-metal technologies will address specific, niche applications, and that most of these applications have not been discovered.
Direct manufacturing of parts, short-run tooling, and high-volume, mass-production tooling, are the applications that the vendors are addressing. Each seeks to provide a solution for what White calls “high-value proposition” applications. Today, this means that the companies are targeting aerospace and medical applications for direct-part production. The companies also target tooling for injection molding and die casting. But as Accufusion’s Coppens states: “This is just the tip of the iceberg. There are many more applications, many of which are unimaginable today.”
The speed of the additive, direct-metal technologies is secondary to the primary gains. As the industry discovered, there is not enough value in rapid tooling to motivate industry to change established manufacturing processes. Instead, direct-metal systems target applications that conventional manufacturing processes cannot achieve.
The most competitive application is the construction of titanium parts for aircraft and medical implants. Accufusion, AeroMet, Arcam AB (Mölndala, Sweden), and MCP Tooling Technologies Ltd. (Staffordshire, England) are all vying for a leadership position in this application. With its new M270 systems, EOS GmbH (Munich, Germany) also plans to enter the fray soon. According to Frank Arcella, chief technical officer of AeroMet: “Titanium is a high-value proposition, especially for aircraft. Consider, for example, a bulkhead that starts as a 3000-lb [1360-kg] billet and is machined to a 150-lb [68-kg] component. With laser-assisted manufacturing [LAM], the time and cost are slashed while the designers can incorporate previously impossible geometry to improve strength-to-weight ratios.” Magnus René, managing director of Arcam, says that direct metal for titanium overcomes the challenges of casting billets and welding parts.
AeroMet has production orders for both the F-15 and C-17 aircraft, and some F-15s are already in the skies with the company’s LAM-made parts. Boeing’s Phantom Works also believes in the potential. According to Arcam, the company has purchased an electron-beam-melting (EBM) system to produce Ti 64 aircraft components. Arcam envisions aircraft with advanced components that could not be cast or machined. To improve strength-to-weight ratios, parts will have an inner scaffold that is skinned with a layer of titanium. “This will lighten and strengthen structural components in a way that no one could have imagined a few years ago,” says René.
Bob Bennett, business development manager for MCP Europe, has focused selective laser melting on the production of complex metal parts. However, he does not plan to unseat high-speed machining or other material-removal processes. Instead, the technology will be an alternative for complex shapes that are challenging for conventional technology.
“No machine answers all the needs of industry,” Bennett states. “Each has its own niche or specialty.” Bennett believes that demand will grow as manufacturers replace established design rules with the potential of direct-metal technologies. Accufusion carries the concept one step further. According to Coppens, “the technology is not the end-all be-all. It will be used in combination with existing technology.” Applying the laser consolidation technology to part and tool construction, he believes that companies will start with a machined part and add material or features to it.
Repair opportunities. Capitalizing on the elimination of constraints and the unique metallurgical properties that are available, Solidica believes that there is a big opportunity in repair. White states: “There are a lot of aging aircraft out there. With direct-metal systems, the parts can be repaired in the field, which reduces downtime and cost.” Similarly, POM Group Inc. (Auburn Hills, MI) applies the direct-metal deposition (DMD) technology to tool repair and reconfiguration.
AeroMet’s Arcella also sees the potential in designing tailored structures. Rather than selecting an alloy and designing a part for the material’s properties, he believes that materials will be designed to deliver performance for a specified design. Brent Stucker of Utah State University (Logan, UT) and Tim Gornet both agree, but in the near term, they believe the primary application will be adding alloys to existing structures. In this application, Gornet and Stucker state that materials will be deposited in specific part regions to improve performance. Gornet calls this concept “blend on the fly alloying.” Stucker is using Optomec Inc.’s (Albuquerque, NM) laser-engineered net-shaping (LENS) system for research of deposition of wear-resistant alloys on the bearing surface of human joint replacement components.
Tailored structure will be simple in the near term, notes Arcella, a process metallurgist, who recognizes an entirely new field of study is needed to make nonmonolithic structures a reality. In agreement, Gornet also states that software tools are unavailable for the definition and analysis of the interaction of multiple alloys and the mathematical progression of one alloy to another.
Direct metal for molds. D-M-E sees the future of MoldFusion in mold components for high-volume production tooling. Partnered with Extrude Hone Corp. (Irwin, PA), D-M-E has worked with Extrude Hone’s ProMetal division for the past five years to develop conformal cooling. MoldFusion abandoned its original plan of offering rapid tooling. When it did, it shifted to an area of much bigger potential gains-reducing cycle time.
Over the past five years, D-M-E has worked on the optimal designs for conformal cooling. Although the concept is simple-convoluted channels that feed coolant to the hot spots in a tool-the science is complex. D-M-E has invested countless hours to devise the optimum configurations for cooling channels. To date, the company has reduced cycle times by upwards of 50%. As with tailored structures, conformal cooling is a new field of study of which there is no pre-existing data.
Rapid tooling’s advantages pale in comparison. Even a small reduction in cycle time will have tremendous benefits. In one study, a 3.5% reduction in cycle time offered a manufacturer more than $100,000 in annual savings.
Gornet also feels that cycle-time reduction is the future. Using DMD to deposit H13 on a copper substrate, his team has achieved 25% reduction in cycle time on a simple tool with an easy-to-mold resin. While POM also uses DMD to repair and reconfigure existing tooling, Gornet believes that the biggest application for metal deposition will be high-thermal-conductivity tooling.
Die casting is perhaps the most extreme of tooling applications for direct metals. In conjunction with the University of Louisville, Gibbs Die Casting (Henderson, KY) is testing and developing the DMD process for shot blocks. The shot block sees the full force of the molten alloy-2900 psi (20 MPa)and 1200°F (649°C). Due to the mass of material at the shot block, its cooling rate dictates the process cycle time. Using a machined copper substrate with DMD-deposited H13 tool steel, Gibbs has realized a 24% reduction in cycle time and a life of 40,000 shots. The company contends that, with additional research, the cycle times and tool life will continue to improve.
Solidica and EOS continue to view rapid tooling as viable, but not for the speed of tool delivery. The benefit is having a self-contained, push-button device to produce prototype or short-run tools. Direct-metal technologies are viable and available, but all of the experts agree that there are major hurdles to overcome. Surprisingly, the biggest barriers have nothing to do with further advancement of the technologies.
Nearly all of the companies cited risk aversion as the primary obstacle. The newness of the technology, its expense, and the lack of performance data justify status quo for manufacturing processes. “Our challenge is finding those companies that are open to new processes, and within those companies finding the visionaries that are will to accept risk for huge gains,” notes MCP’s Bennett. And Shellabear adds: “Inertia and conservatism are against us. We are entering a field where the fundamental processes are long established and where failure is not an option.”
The design freedom afforded by direct-metal systems is a huge advantage, but is currently a big barrier, according to EOS’ Shellabear. “To realize all of the potential of the technology, parts and tools need to be designed to capitalize on the freedom of design,” he says. If parts and tools are designed as they’ve always been, the advantages are minimized. One solution is a new field of university studies. Shellabear believes designers must be taught how to design parts for additive technologies. He also believes that having college texts with this field of study offers validation to all others in design and manufacturing. “If it’s taught in universities, the concept is validated.”
Shellabear and others acknowledge that there are newfound limitations to the direct-metal technologies. For further progression, it’s agreed that these will need to be addressed. However, the companies also contend that parts and tools can be designed such that the limitations are no longer an issue. He cites the issue of near-net shape. “Due to surface finish and accuracy, many parts need secondary machining. But consider the possibility of combining 10 parts into one, and only have a handful of easily machined surfaces instead of 30 tolerance-sensitive features,” says Shellabear.
Direct-metal systems will not replace machining, molding, and casting, but will be complementary tools that augment the processes used in today’s machine and molding shops.
Broad use in 3-5 years may be a challenge, but with industry’s support, it will not be much longer than that for direct metal to be a common production practice for parts and tools. For now, it seems to be the visionaries and risk-takers who are reaping the rewards.
This article was first published in the October 2004 edition of Manufacturing Engineering magazine.