Superlative parts crowned at powder-metal competition

Members of the Metal Powder Industries Federation (MPIF), Princeton, N.J., once again prove inventive powder-metal (P/M) parts can outperform their machined, stamped, cast, and forged counterparts. Parts winning the organization's annual competition are made by conventional press-and-sinter technology, warm compaction, and metal injection molding. They perform in applications ranging from automotive and outdoor power equipment, sporting goods, and electrical devices, to dental products and lab equipment.

The 2005 International P/M Design Competition highlights outstanding examples of how powder metallurgy brings engineering benefits.

Grand prize winners

The Ferrous grand prize went to BorgWarner Powdered Metals Inc., Livonia, Mich., and its customer BorgWarner Transmission Systems, Auburn Hills, Mich., for input and third-position outer races used in GM's 4T65-E transmissions. The parts are selectively densified on the surface of the pocket to thwart wear. The races are heat treated to minimize part distortion and meet stringent strength and fatigue-life specs. Inside diameters of both parts have six pocket forms that hold locking pawl and spring elements. The parts sport an ultimate heat-treated tensile strength of 131 kpsi, an impact energy of 12 ft-lb, and a minimum 32 HRC hardness. P/M dropped part cost 20% compared to forged outer races.

A complex, 316 stainless-steel support cover used in a high-security military application captured the Stainless Steel grand prize. Webster-Hoff Corp., Glendale Heights, Ill., forms the cover as a net shape (except for deburring) with flatness and slot width tolerances of 0.005 in.

During compaction, technicians measure two level dimensions and part weight hourly for statistical process control. The levels maintain a CPK of 1.33 and weight is held to within 3% with a CPK of less than one. The cover has a density of 6.5 gm/cm ³ , a 59 HRB hardness, and ultimate tensile and yield strengths of 41 and 34 kpsi, respectively.

Advanced Materials Technologies Pte. Ltd., Singapore, garnered the Injection Molded grand prize for a highly complex copper connector used in an electrical appliance plug and adapter. Singapore-based Eubiq Pte. Ltd. designed the metal injection-molded connector to let existing three-pin plugs engage anywhere along a power track. The connector has a density of 8.8 gm/cm ³ , an elongation of 45%, and respective ultimate tensile and yield strengths 36 and 8.7 kpsi. MIM let Eubiq shave 20% off part cost compared to stamped, turned, machined, and press fit alternatives.

A camshaft sprocket used in a 4.0-liter V6 engine raced away with the Overseas grand prize. Sinterstahl Füssen GmbH, Füssen, Germany, devised innovative tooling with three lower and two upper punches to form the net shape sprocket from an iron carbon-molybdenum-chromium alloy. This is the first known application of a chromium-based sinter-hardened material for a camshaft drive. The sprocket features a density of 7.0 gm/cm ³ and a transverse rupture strength of 206 kpsi as well as 119 kpsi tensile and 99 kpsi yield strengths. P/M gave BorgWarner Engine Group Morse Tec Europe S.r.l., Milan, Italy a cost savings of more than 10%.

A 16-part assembly from Burgess-Norton Mfg Co., Geneva, Ill., blew away the Innovative Functional Assembly competition. The grand-prize-winning free-wheel steering-system axle assembly for a snowblower weighs in at 5.9 lb and consists of a stamped steel frame, bronze and plastic bearings, and a wrought steel axle. The assembly functions as an on-demand operator-controlled differential traction system. The P/M parts range from single-level to intricate multilevel designs. All parts are close to net shape and have a density range of 6.7 to 6.8 gm/cm ³ . Secondary operations are limited to vibratory deburring and honing. P/M halved part cost compared to machine castings and wrought materials.

MPIF Awards of distinction

A three-level range sleeve used in a differential in a Magna Powertrain NPG 226 transfer case took the Ferrous award of distinction. Keystone Powdered Metal Co., St. Marys, Pa., forms the 2-lb part via warm compaction to a density of 7.2 gm/cm ³ . Magna Powertrain USA Inc. (formerly Magna Drivetrain of America Inc.), East Syracuse, N.Y. , is the first to use P/M in a transfer-case differential for GMC Envoys and Chevrolet Blazers. The part links the transmission and the wheels, transferring power to the rear wheels when in two-wheel-drive mode and into all four wheels when in four-wheel drive. All three splines are net formed along with the pointed teeth. Properties include ultimate tensile and yield strengths of 18 kpsi and a typical 40 HRC hardness. P/M dropped part cost more than 30%.

A second ferrous award of distinction went to Pennsylvania-based, GKN Sinter Metals-Emporium, for a differential cap made for the Chrysler Group. Two caps go into the differential gear assembly in the rear axle of Jeep Grand Cherokees, Wranglers, Liberties, Dakotas, and Durangos. It's the first time that a proprietary machinable P/M material was used in a high-volume, automotive differential cap. GKN assembles the parts with cast iron housings and simultaneously bimetal machines inside diameter bores and threading. The part is made to a density of 6.7 gm/cm ³ in the arch. It has an ultimate tensile strength of 70 kpsi, an elongation of 3%, a fatigue endurance limit of 26 kpsi, and a 75 HRB apparent hardness.

GKN uses a patented Z-loc technology that reportedly improves subassembly alignment between the differential cap and the case. P/M let GKN eliminate five secondary operations previously needed on the casting it replaced.

Asco Sintering Co., Commerce, Calif., won the stainless steel award of distinction for a safety cam made for Buck Knives, Post Falls, Idaho. The cam operates in several knife models using Buck's new ASAP one-handed quick-release system for opening the knife blade; the blade cannot open until the safety cam has been released. Asco devised an innovative tool to form the complex net-shape part from 410 stainless steel. The cam sports a 6.5 gm/cm ³ density, a 23 HRC hardness, and ultimate tensile yield strengths of105 and 90 kpsi, respectively.

FloMet LLC, DeLand, Fla., and its customer SDS Ormco, Orange, Calif., garnered the first of two Injection Molding awards of distinction for a Damon 3 Molar Buccal Tube system used in orthodontic braces. The system consists of 32 MIM brackets and two MIM slides made from 17-4PH stainless steel. The parts are heat treated and have an ultimate tensile strength of 185 kpsi, yield strength of 160 kpsi, 7% elongation, and range in hardness from 38 to 42 HRC. The tube system was first introduced in the all-metal Damon self-ligating orthodontic appliance.

MIMflow Technologies LLC, Euclid, Ohio, and its customer, The Star Dental div. of DentalEZ Corp., Lancaster, Pa., earned the second Injection Molding award of distinction for a manifold used in a handheld fiber-optic swivel dental system that delivers air, water, and fiber-optic light simultaneously into a patient's mouth. The complex 17-4PH stainless-steel part has a density of 6.7 gm/cm ³ and features 19 critical dimension callouts that require tolerances be held to ±0.003 in. or less. The part has seven cores including a 0.023-in. core that must be drilled in the green state. That's because it features a compound plane to the centerline that could not be machined as a postsintering operation due to the small diameter of the drill. MIM replaced a machined part that had yielded a useable rate of only 60%.

A kinematic optical mount used in laboratory equipment won an Innovative Functional Assembly award of distinction. Precision Powdered Metal Parts Inc., Pomona, Calif., forms the 316L stainless-steel part that is fabricated to a density of 6.4 gm/cm ³ with a yield strength of 25 kpsi. The optical mount holds a mirror lens that

directs and deflects a laser beam with two 100 pitch-thread adjustments. The assembly replaces a machined aluminum part. Secondary operations include deburring, drilling, tapping, and blasting with glass beads to improve appearance.

Engineered Sinterings & Plastics Inc. (ESP), Watertown, Conn., won a second Innovative Functional Assembly award of distinction for a lower-arm assembly used in a proprietary application in the publishing and copying industry. The assembly consists of six complex P/M parts; plastic, laser cut, steel plate, and screw machined parts; and standard purchased components. The four P/M steel parts are made to a minimum density of 6.8 gm/cm ³ and are steam treated. The two 316 stainless-steel parts are made to a typical density of 6.6 gm/cm ³ . The assembly was originally designed with all of the components either machined or stamped. ESP designed and built the plastic and P/M molds, machining fixtures, and inspection and true-position fixtures.