New powder press is petite but powerful
Size does matter at Mii Technologies (West Lebanon, NH). This maker of powder metal components and materials has created a hydraulic press that packs more than twice the clamping force of conventional powder metal machinery into a fraction of the space.
Make that a tiny fraction. While a 220-ton powder metal press typically stands more than 20 feet high and has the girth of a garbage truck, the new 458-ton Mii press takes up less room than a kitchen refrigerator. "We traded brute force for a better design," says Glenn Beane, Mii's president and the machine's principle designer.
More than just an effort in downsizing, the press represents just one part of an modular approach to powder metal manufacturing. In contrast to the usual collection of stand-alone presses, Mii's manufacturing system uses a centralized hydraulic "power plant" to drive a plant of small, powerful presses. Individual machines tap into the central plant via a 450 psi feeder line-a procedure Beane likens to "plugging in an extension cord." And with the bulk of the hydraulics removed from the press, only a relatively small clamping mechanism remains.
Mii's manufacturing cells-or "docking stations," as Beane calls them-also employ unique material-handling capabilities to boost the uniformity that sometimes eludes metal powder processes. For part-to-part uniformity, Mii's cells have a gravimetric feeding system controls the amount of powder that enters the die. "It's accurate to within one-tenth of a gram," Beane notes. And to achieve a uniform density within a part, Mii developed a patented vacuum system to fluidize the powdered metal in the die, evenly distributing it.
The system compacts material differently than a traditional press, too. As Beane explains, traditional presses drive the punches in lockstep without regard for localized resistance in the die-which result from part geometry or uneven powder distribution. He says this condition can strain individual punches, ruining parts at best and breaking tooling at worst. Mii's system backs each punch with a hydraulic piston. Each one operates individually with closed loop control of pressure, distance, and time.
A PC-based controller runs the entire system-everything from the material handling systems to the punchpiston controls.
Aluminum takes a breath
Three new products have been added to the Metapor line of "breathable" porous aluminum. A new high-temperature version (BF210 AL) boosts the Metapor's continuous operating temperature to 410F from a previous maximum of 226F. A new high-density variety (HD100 AL) raises the material's density to 1.10 oz/inch3 from a previous maximum of 1.04 oz/inch3. And a new highly porous form of the material (Metapor Macro) offers ten times as much airflow as previous grades. Applications for porous aluminum include thermoforming tools, vacuum clamping systems, and air-cushion devices.
A casting comeback
Diecasting complex magnesium parts on hot chamber four-slide machines isn't exactly new. Dynacast Inc. has been doing it for years-mostly in Germany with just a handful of jobs here in North America. "Those projects came to their natural end, and we're not currently running our four-slide machines here," reports Mike Torti, the company's market development director. But based on a projected demand for small, precision magnesium parts for electronics, telecommunications, and even sporting goods applications, Dynacast will soon take the process out of its American mothballs.
According to Torti, the company will next year re-launch its four-slide capabilities in a new North American facility. Torti concedes that the market for small magnesium components "hasn't been huge," given that this metal shines best in applications that benefit from its high strength-to-weight ratio. Yet, he points to opportunities for precision-cast magnesium to replace plastics in parts such as connectors. "We increasingly compete against plastic parts that have failed," Torti says, noting the first four slide job here was an automotive electrical connector.
And four-slide diecasting may be well-positioned to take on injection molding when it comes to producing small components. According to Torti, the four-slide process uses precision single-cavity tools and can hold dimensional tolerances in the neighborhood of plus or minus 0.001 inch. And four slides, oriented in a 90-degree fashion, allow the process to produce a wide range of part features straight out of the die. "We can near net-shape parts with complex geometries without the need for secondary operations," Torti says.
Metal powders get wet
Hoeganaes Corp. now makes fine metal powders using a water atomization process that produces a particle size averaging under 20 microns. Intended as a less costly alternative to gas-atomized and carbonyl powders, the new metal powders occupy the middle ground between the 40-micron size of most water-atomized particles and 4 microns of the more expensive technologies. The process is currently producing two products, 316L stainless steel and 17-4 PH. Four other products are now under development. Applications for the new powders include injection molding and magneto-rheological fluids.
Alloy 7068 hits the mainstream
Good news for design engineers looking for small to medium size quantities of Tennalum's alloy 7068, a high-strength aluminum alloy (yield strength of 99 ksi; UTS of 104 ksi in the T6 temper) designed to compete with another high-performance material, alloy 7075. Castle Metals is now stocking 7068 as a standard product, which has been making its way into applications ranging from race cars to mountain bikes-anywhere, in fact where a high strength-to-weight ratio is sought-in a round condition ranging from 0.5 to 2 inches in diameter.
Chemistry was the key. Zinc is the primary alloying element, with magnesium and copper being the other two vital elements involved in obtaining higher strength, says Roy Coats, quality manager. "The strength to weight ratio of 7068 is on the order of 10 to 15% better than alloy 7075," says Coats. "The upshot? Design engineers need less material to achieve the same performance."
High-strength aluminum alloys (7000 series) with a standard T6 temper are not known for their corrosion resistance, so it was naturally a concern in the development of the new alloy, says Coats. But he notes that the stress corrosion cracking ratings of 7068 are comparable to 7075.