Automotive Gear Manufacturing
engine will have four cylinders and the average automatic transmission—the most popular choice of consumers—will have eight (or more) gears. To illustrate the current demand for gears, Hyundai sub- sidiary Powertech America (West Point, GA) is set to produce approximately 650,000 automatic transmissions this year. It will do so with fewer than 500 employees, including adminis- trators, and a high level of automation.
sion of each gear component is directly linked to the subse- quent fuel economy of the vehicle. Plus the transmission has not become any larger, requiring more precise components to do the job. We definitely see a tightening of the specs and tolerances in gear manufacturing in the US following a trend we have been seeing in Europe for quite some time.” There are other ramifications of the downsizing, accord-
ing to Walter Friedrich, president of German Machine Tools of America (GMTA; Ann Arbor, MI), and Scott Knoy, GMTA vice president of sales.
Size Matters
Scudding, as shown here on a Profilator, is an operation similar to hobbing, but which uses sharper cutter style tools.
With such demand, the need to produce transmission gears quickly and efficiently is great. And because these transmission designs will need to fit more gears in a case no bigger than the cases currently used, the gears will be smaller.
Quality is Even More Important Now
“This means,” said Karl Schaeferling, Director Product Management—Honing, Shaving & Chamfering Solutions of Gleason Corp. (Rochester, NY), “that the torque density for the gearboxes will be higher compared to the past. This implies a higher quality of … gearboxes in general and, of course, for the gears, too. The use of fine finishing processes will increase, specific gear flank modifications will be increas- ing and finally the surface quality has to be higher. “In general, the need for gear grinding and gear honing will increase to fulfill these tasks.” Peter Loetzner, president and CEO of EMAG LLC (Farming- ton Hills, MI), agreed that there is a need to increase preci- sion: “The higher fuel economy requirements drive the need for more gears or gear combinations. The quality and preci-
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”If indeed gears and gearboxes get smaller, tools and fixtures will get smaller, too,” said Friedrich. That likely would mean smaller machines and possibly reduced costs. “Conversely,” Knoy, said, “the smaller gearboxes have to be robust and perform at higher levels than the older, larger boxes as far as durability, noise and length of service, so advanced steels will be used for these new gearboxes and the development of the metal products will result in increased tool costs to ma- chine the exotic metal. New cutting tool steels will be required, which drives R&D cost as well as the increased cost of these new tool steels. Additionally, the new cutting processes will require stiffer and more rigid machinery that can handle the high torque and vibration associated with machining these new varieties of metal. These changes will also be necessary on the fixtures and tooling used to hold and handle these new smaller gears.” The levels of precision and accuracy are not something with which gear machining manufacturers are unfamiliar. “For a long while,” said David Goodfellow, president of Star SU LLC (Hoffman Estates, IL), “gears ground for accuracy have been prevalent in aerospace, turbine, and with marine propul- sion gears. With the onset of eight and nine-speed transmissions running at much higher rpm, power density and sound issues have the automotive manufacturers calling for hard finishing.” Goodfellow sees other trends in automotive gear produc- tion such as “carbide hobbing, higher speed machining and honing.” He added that the new generation of gears “will be more challenging to workholding fixtures because the smaller gears will be more difficult to clamp and maintain stiffness while maintaining high accuracy and productivity.”
An Emphasis on Throughput
Productivity is a topic that comes up often in discussing automotive gears.
Photo courtesy GMTA
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