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Automated pouring at Signicast Corp., Hartford, WI.

The Secrets of Investment Casting

Oct. 26, 2011
One segment of the metalcasting industry is setting a high-tech, high-value example for the rest, but learning how and why is a challenge.
IBC Engineered Materials relocated its investment casting foundry earlier this year, and is producing a series of aerospace components and commercial products in beryllium-aluminum alloys — about which details are well guarded.
Signicast’s Module 4 was completed in 2006, and produces investment castings in low-alloy carbon steel, tool steel, and 300 and 400 series stainless steels. It is the most highly automated installation at the Hartford, WI, plant, though a new module planned for a 2013 start may exceed its capabilities.
Signicast’s Module 5 at Hartford, WI, is a self-contained machining, assembly, vibratory tumbling, and painting operation. Investment castings are delivered there by an automated system for finishing, according to the requirements of the order. The current expansion at the Hartford, WI, ferrous foundry will include a new secondary processing operation.

Metalcasters understand each other. The industry brings together individuals for what often is a lifetime vocation. They know each other through their work, and they know the problems and challenges of the work that their colleagues do. There aren’t too many secrets among them. There is an exception though in the field of investment casting, where even simple questions are met with long pauses and stock replies: “I can’t really get into that,” or, “That’s proprietary information.”

It’s no secret that investment casting is thriving. For an industry with ancient roots, it is a window to the future. And while the technique is not new, advances in process control and material science have elevated investment casting to the high-value realm — making investment casters the frequent object of investment experts. Private-equity acquisitions of Triumph Precision Castings and Consolidated Precision Products Corp. are recent examples of this, both firms being manufacturers of aerospace components.

The importance of such capabilities makes the secrets of investment casting even more valuable, valuable enough to drive new capital investments. Chromalloy Corp., the producer of aircraft engine components, started a new, $30-million foundry in Tampa late last year on the impetus of rising demand from the commercial aircraft market, and with its sights set on the industrial gas turbine market, too. Soon, an adjacent ceramic core plant will be added.

Generally, investment casting is a simple process: Working from a master pattern, a mold is made from which a series of wax or ceramic patterns are produced. These patterns are arranged into one complex assemblage, and this cluster is given a refractory ceramic coating. Once the requisite coating thickness is achieved and the ceramic is hardened, the wax is burnt out from the shell molds and the latter are preheated in preparation for filling with molten metal. Pouring may be done in various ways, and solidification may require special production or handling steps, such as vacuum processing. Finished castings are removed from the shell by vibration, blasting, chemical treatment, or other methods.

Obviously, investment casting allows for lots of variables in technique, and the specifics of metallurgy or ceramic formulation, or the vacuum or pouring processes, are among the secrets to success.

High-Tech Potential

A more recent example than Chromalloy is IBC Engineered Materials, a company that focuses on beryllium: investment casting offers particular opportunities to design and manufacture parts in those lightweight alloys. Early last year the Vancouver- based IBC Advanced Alloys bought Beralcast Corp., which had a series of manifestations over recent decades, but its primary value lay in the techniques it had developed for producing beryllium-aluminum investment castings.

Beryllium is light, but rigid, and thermally stable, which makes it a valuable material for advanced aircraft designs, weapons systems, and communication satellites.

IBC recruited Ray White to lead its acquisition, which is known as IBC Engineered Materials now. At that time, White was an executive with L3 Communications, a large defense contractor supplying electronic control and communication systems. But, his previous experience had been with the Beralcast organization; he’s an inventor and patent-holder for the technology that makes it possible to produce investment castings in beryllium-aluminum.

The alloy in discussion is normally 65% beryllium by weight, as White explained, with the balance being aluminum and some small additions of other elements that help it to achieve castability.

“It means we have an alloy that is very lightweight and that is also very stiff — its specific stiffness is phenomenal,” White offered, “and so it finds its way into a lot of aerospace and defense applications, including optic systems, gimbals, night sights, forward-looking infrared systems, anything where you need something that is light, with higher stiffness.”

Some applications are not in aerospace at all. IBC EM supplies a linkage fixture for wire-ball binding machines used to ‘print’ semiconductors.

“In layman’s terms, (Al-Be) is 22% lighter than aluminum, and it has the stiffness of steel,” he continued, but cautiously. “It’s a very unique, impressive alloy. And to be able to investment cast that, if you’d look at a phase diagram anyone in the metallurgical world would tell you that it couldn’t be done. But, we found a way to do it. There is no one else in the U.S. that has yet been able to investment-cast Al-Be alloys.”

Beralcast had been operating at what White described as an overdeveloped pilot plant in Concord, MA, a very large installation with scattered operations, as well as some environmental hazards that were the result of some nuclear materials processing performed by one of the previous proprietors. IBC EM needed a new plant, so last January it began relocating to a site in Wilmington, MA.

“We actually took three warehouses and turned them into roughly 70,000-ft2 of manufacturing space,” White said. “It was six months of work: we moved all the equipment from the old facility, and bought some new equipment and installed that. And we were up and operational in June.”

But, White is circumspect about detailing the operations. “We’ve got all the standard investment casting equipment,” he allowed. IBC produces its own casting shells, and the plant has a complete wax injection system. A flash-firing de-waxing unit is on order for delivery soon. “Our foundry is really the special area,” according to White. “Because we are melting beryllium it’s kind of contained, if you will. It’s a state-of-the-art facility with all the ventilation systems that are required for working with beryllium safely, and we have a very large (or, what we consider large) vacuum induction melting furnace.”

All of IBC’s alloys are produced in the VIM, and while White indicated some interest in alternative melting technologies that would not involve a vacuum and still be capable of pouring into an investment mold, he could not elaborate.

Because beryllium is so light it makes no sense to measure tonnage. “We’re capable of casting a beryllium-aluminum component that is 1 m3, which is pretty large considering the density of the alloy,” he explained, Between aerospace and commercial products White estimated the new plant is producing 300-400 finished products weekly — or about 20% of its potential.

The effort to relocate and recertify with customers has been rather smooth, and the growth strategy involves scaling up the production volume for current customers as well as qualifying new ones. “We are working hard at that, but it will take some time, particularly with the aerospace customers,” he observed. “They’re starting to come in now, and I’m very optimistic about that.”

Aerospace customers have a significant demand for light, rigid investment castings, he said, and IBC has been “fielding lots of phone calls, attending lots of shows, and visiting lots of people” to tell the market about its castings.

“The alternative to what we’re making as an investment casting is a hog-out of beryllium-aluminum,” White pointed out, “and there’s no comparison. You can take an 80-lb block of berylliumaluminum and machine it out, and end up with a 5-lb part. We can investment cast that part at 5.2 lb and do very little machining.”

Efficiency in product design and production cost is the advantage IBC Engineered Materials is offering to aerospace customers, domestically and globally, confident that no one else can match its proprietary achievements.

What is it about IBC’s investment casting that makes its Al-Be products so different? Is it process controls? Casting techniques? “Yes, but I don’t think I can tell you, unfortunately,” White said. “It involves just about every aspect of the investment casing process, including the up-front engineering, meaning tailoring designs, metallurgy, moldmaking, gating designs, the formulations of the shell coating, the casting process, … all of it is specifically designed for Al-Be alloys. Process controls are critical.”

Strictly Commercial

Another example of successful investment casting is Signicast Investment Castings, in Hartford, WI, one of the largestvolume producers in the market segment. However, its strategy is not linked to aerospace or difficult-to-handle alloys. Its customers build agricultural equipment, pumps and valves, for example. “We are strictly a commercial investment casting foundry, and we believe that we can continue to grow that way. It’s a market that we have been very successful in,” v.p. of sales Todd Mc- Donald affirmed. Signicast’s $50-million capacity expansion now underway is proof of that.

One factor in Signicast’s success is its organizational model, which is based on six manufacturing modules at two locations, in Milwaukee and Hartford. The modules resulted from a series of expansions since 1997, and each module is a self-contained production process. Each expansion added to the production capabilities and the levels of automation. In Hartford, four modules produce investment castings and a fifth handles secondary processes, like finish machining, product assembly, or powder coating. The Milwaukee plant produces investment castings plus wax and ceramic cores, with heat-treating, NDT, and rapid prototyping capability, too.

Investment casting aligns well with the concept of work cells, and each of Signicast’s investment casting modules may be understood as a high-volume, multifunction work cell with a specific range of alloys and product sizes. By effective management and organization Signicast is able to produce castings in a very wide range of carbon, stainless, and specialty steel alloys, from pocket-sized components to parts weighing hundreds of pounds.

“We’ve built Signicast, through all the expansions, to create a wide scope, as wide as possible, everything from part size and weight and configuration to alloys,” McDonald explained. “It’s because we have 470 active customers and across that customer base we have to be able to do it all. We cannot do somebody’s high-volume work without doing the low-volume work, too. And we cannot tell a customer that we can do some alloys but not their alloy. So, it’s forced us to be very flexible.”

Signicast is flexible, but every process step is reliable, too. At Hartford, an automatic storage and retrieval system (ASRS) delivers materials and products from station to station. Robots are used extensively for the numerous stages of investment casting (dipping, pouring, cleaning), and automated sampling and data storage ensures quality control. The scope of automation has increased with each module expansion, which have taken place at intervals of four years or so, as McDonald noted. Module 4, debuting in 2006, is the largest and most innovative installation to date – and likely to be surpassed with the current expansion.

Signicast broke ground this year on a large site adjacent to the Hartford plant, and long-term plans foresee a total of five more modules there. Construction is underway now for the first of two modules, a new secondary processing cell that will be complete by mid 2012. Following that will be the company’s sixth investment casting cell, Module 7, in operation by the summer of 2013.

McDonald predicted Module 7 would be Signicast’s “next big leap” in performance and capabilities, though he declined to be specific “for proprietary reasons.”

“We’ve taken what everyone knows as traditional investment casting processes,” he said, “and we’ve improved in every one of those areas. So, the same general processes will be used but with technology enhancements and processing improvements.”

The point seems to be that investment casting is Signicast’s business, but executing the process efficiently is its market niche. Because it’s not producing specialty products, Signicast must compete with both domestic and offshore foundries — meaning it must be as design-conscious and qualityfocused as its North American competitors, and as affordable as any foreign supplier.

Investment casting gives Signicast a chance to avoid commoditization of its products. “We try to avoid that by designing a better part,” McDonald said, “but really by working with our customers to make it more manufacture-able, meaning finding out their assembly requirements, adding features, reducing their labor content, and making it easier for them to produce their fnished products. And we can do that very easily with investment castings.”

If Signicast’s customers can reduce assembly or manufacturing time, and have improved performance from the castings they buy, they won’t be inclined to settle for another, lower-cost product.

“At the same time there are parts out there that are simple,” McDonald maintained, “and perform the function that they need to perform very well.” Signicast knows it must maintain a competitive price on its castings to keep those buyers from sourcing elsewhere. Signicast understands that the secret to its success making all the critical factors — process technology, automation, customer service — work toward that goal.