Magnesium investment casting is notoriously challenging due to the metal’s reactivity, pour sensitivity, and tight process controls. As a result, few foundries in North America are willing to work with it. 

One Michigan foundry, AFS Corporate Member Aristo-Cast Inc., not only accepts the challenge—but thrives on it. With more than two decades of experience producing magnesium castings, the company has developed a reputation for precision, consistency, and production-grade repeatability.

That expertise helped earn the company an Outstanding Achievement recognition in the 2025 AFS Casting Competition for the Atlas Aft, Main, and Front Housings created for Steiner eOptics. These components house electrical and optical elements for a laser-aiming device mounted to a rifle.

Traditionally, housings of this type would have been machined from aluminum billets. However, Steiner wanted its Atlas line to be lighter and more ergonomic than the traditional housing. Magnesium quickly emerged as a promising alternative, leading Steiner to contact Aristo-Cast through the company’s website. 

“Magnesium was very attractive because it provides them excellent lightweighting characteristics and absorbs vibration well—an important consideration when you’re mounting a device on the barrel of a rifle,” said Phillip Messing, an investment casting engineer at Aristo-Cast. “They needed our expertise precisely because they had no prior experience with magnesium.”

Designing for Lightweight Strength

Steiner’s engineering team came in with ambitious goals: complex geometry, ergonomic contours, and the lightest structure possible. Aristo-Cast provided a detailed set of investment casting design guidelines covering minimum wall thickness, draft allowances, and other key parameters. 

“We would provide the key characteristics required for investment casting,” Messing said. “They designed a finished part for us to review, and we worked backward to ensure it was fully castable.”

Once the designs were approved, Aristo-Cast produced an initial run of 25 prototype castings for each detail. The company employs both traditional metal casting processes and newer additive manufacturing tools and techniques—also known as 3D printing—to create its products.

The team printed the Atlas patterns on 3D Systems 2500 IC wax printers, using both standard and soluble wax. The soluble wax was then dissolved with isopropyl alcohol to reveal the intricate internal geometries—features that would have been difficult, if not impossible, to achieve using only traditional processes.

Following pattern production, the project moved into Aristo-Cast’s magnesium investment casting workflow.

Casting Magnesium

Because magnesium is highly reactive and has a high pour temperature, it requires specialized handling, including a multilayer ceramic shell system and tightly controlled environmental conditions––which Aristo-Cast has significant experience managing. 

Even so, these housings pushed the limits of the process. The parts included wall sections as thin as 0.040 in., and early prototype pours revealed intermittent non-fill and pockets of porosity that were not attributable to gating or shell issues. These inconsistencies prompted further investigation into alloy handling and atmospheric conditions. 

“We discovered that the cover gas we were using was not dry gas,” Messing said. “Moisture in the cover gas can introduce hydrogen porosity and oxide formation in magnesium. Switching to a verified dry gas supply significantly stabilized metal quality.” 

Aristo-Cast also implemented reusable steel filters that were added to clean the metal stream and reduce inclusions. Vent holes were drilled into the three-bar wax tree to improve gas evacuation during the fill. Together these changes—cleaner metal, improved venting, and a more controlled pour environment—significantly improved the fill consistency and reduced the unpredictable porosity. 

Secondary Operations

Producing the castings was only the start, however, as the housings also required several secondary operations, including heat treat, machining, conversion coating, double impregnation, and a final Cerakote finish. Once complete, the components were sent over to Steiner for validation testing. 

“They identified most issues during assembly, based largely on how the parts were processed,” Messing said. 

Steiner conducted nitrogen-pressure and vacuum-leak tests to ensure each component was fully sealed. Any leak or structural weakness in the housing could compromise the sensitive electronic and optical equipment inside. In addition, tests were conducted to make sure the product could withstand the real-world conditions to which it would be subjected in use, such as recoil, vibration, and temperature fluctuations. 

“There are still adjustments here and there, but most of the quality-related issues have been resolved,” Messing said. “At this point, we’re mainly addressing occasional unforeseen issues that arise during production.”

Leaning into R&D

The project with Steiner showcased Aristo-Cast’s production capabilities, but it also highlighted one of the company’s core strengths: research and development. 

“I’d say that was well in line with what we do every day,” Messing said. “We basically live and breathe R&D.”

Over the years, Aristo-Cast has completed numerous complex geometry projects involving computer-generated topography that allowed Messing to leverage his 15 years of technical CAD experience. 

Aristo-Cast is also always looking for ways to expand their capabilities and integrate new technologies alongside traditional foundry practices. 

When it was founded in 1994, Aristo-Cast operated out of a rented warehouse in Romeo, Michigan. “It was only 8,000 sq. ft. with 10-ft. ceilings,” Messing said. “Not really ideal for foundry operations at all.” Aristo-Cast moved into its purpose-built foundry in 1998 in Almont.  Additional expansion followed in 2003 with the construction of a dedicated facility for additive manufacturing, patterns, tool making, and magnesium pouring. Today, the company operates in approximately 35,000 sq. ft.—enough space to balance growth in both the R&D work and production programs. 

Steiner’s Atlas Aft, Main, and Front Housings align squarely with that growth strategy. With projected demand of up to 15,000 sets per year, the partnership represents a long-term opportunity for both Aristo-Cast and Steiner.

Winners’ Circle

For Aristo-Cast, the decision to submit this housing to the AFS Casting Competition was an easy decision. 

“It was magnesium with extremely complex features that you really can’t make any other way than investment casting,” Messing said.

The judges agreed, awarding the highly detailed castings the third highest score overall and second place in the Conversion category. 

Messing also noted that the recognition is just one benefit of being a part of the American Foundry Society. The larger benefit is the ability to use it as a communication platform and a forum to exchange ideas with others in the industry.

“What it really comes down to is we wanted to help revolutionize this 6,000-plus year-old industry as a whole,” he said. CS

Portions of this information were adapted with permission from materials prepared by the International Magnesium Association and the North American Die Casting Association.

A Closer Look at the Benefits 
of Casting with Magnesium

Magnesium remains one of the most challenging alloys to cast, yet it offers a compelling list of advantages for engineers seeking lightweight strength and complex geometry. When paired with tightly controlled processes, it can unlock design opportunities that are difficult—or even impossible—to achieve with machined billet components.

Magnesium’s appeal lies in its exceptional strength-to-weight ratio. At roughly two-thirds the density of aluminum, it enables significant mass reduction without compromising structural integrity. For weapon-mounted electronics, like the Atlas Aft Housing, this translates directly into improved ergonomics, reduced operator fatigue, and better balance on the rifle. 

Its strength and ability to absorb vibration, like those from a machine or a rifle’s recoil, leads to reduced wear and provides significant protection for expensive electronic components.

Properties Worth Considering

Because of their properties, magnesium alloys can provide a casting designer with several advantages over other lightweight alloys:

Weight—The lightest of all structural metals, magnesium preserves the light weight of a design without sacrificing strength and rigidity. This benefit is important when portability is a key element of the product design, such as with chainsaws, pneumatic nailers, circular saws, luggage, laptop computers, and cellular phones. Automobiles and other transportation equipment continue to take advantage of magnesium’s low density in expanding application areas ranging from under-hood and driveline uses found in engine brackets and transfer cases to numerous interior parts, such as steering column components, pedal brackets, instrument panel supports and seating.

Damping Capacity—Magnesium is unique among metals because of its ability to absorb energy. Increased vibration absorption capacity provides for quieter operation of equipment when magnesium castings are used for housings and enclosures.

Dimensional Stability—Annealing, artificial-aging or stress-relieving treatments normally are not necessary to achieve stable final dimensions. Metallurgical changes in the structure of some metals can affect dimensions after prolonged exposure to elevated temperatures, but this is not the case with magnesium alloys. As a result, there have been few problems associated with the dimensional change of castings in assemblies. Shrinkage rates are more consistent and predictable in magnesium than in other nonferrous metals. Components release from the die (in the die casting process) with minimal force and distortion; hence they have minimal residual casting stress.

Impact and Dent Resistance—The elastic energy absorption characteristics of magnesium result in good impact and dent resistance and energy management, which is one reason magnesium castings can be used for automotive safety-related applications, such as air bag systems. Portable tools and handheld electronics also benefit from this combination of properties, offering mechanical shock resistance.

Anti-Galling—Magnesium alloys possess a low galling tendency and can be used as a bearing surface in conjunction with a shaft hardness above 400 Brinell.

Design Considerations

When evaluating the various alloys and processes for a magnesium casting, the end-use application, post-casting operations, and tooling costs should be considered to obtain a quality, low-cost component.

Specifically, keep in mind the following attributes of magnesium:

High Stiffness-to-Weight Ratio—This characteristic is important where resistance to deflection is desired in a lightweight component.

Improved Die Life—Unlike molten aluminum, molten magnesium does not react with tool steels, resulting in longer die life and increased productivity. Because of low erosion and heat input, which reduce the propensity for thermal fatigue (heat checking of the die), casting magnesium can achieve three to four times the die life than can be achieved with aluminum.

Machining—Magnesium is recognized as the easiest of structural metals to machine and is the standard of the cutting tool industry when comparing machinability of metals. The low power requirements for machining magnesium alloys permit the use of deeper cuts and higher feed rates, thus permitting fast and efficient machining when compared to other metals. Magnesium alloys also normally produce well-broken chips, which are easy to handle.