Gear Production

SEP 2013

Gear Production

Issue link: http://gear.epubxp.com/i/155418

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Transmission subassembly line at ITP II. "On an external gear, almost without fail, hobbing is the chosen process because it is clearly the most economical, and it is very accurate. Even for one of the transmissions Rick is responsible for, the gear train is fnished with hobbing. There are aerospace gears fnished with hobbing." And yes, they both acknowledge that hobbing is generally a roughing process. Seems like technology has come a long way since 1889. But typically there is rolling, shaving or grinding used. Wade says that what they do comes down to a few simple questions: "What is the product going to be used for? How much money are you going to spend on it? How are you equipped?" He adds, "With time and money you can do anything you want to do. But we have operating constraints as a business. If you violate the basics, that's where you get into trouble." Among those basics, he explains, is the understanding of what happens when a blank goes through the processes to become a gear. Wade says, "There is a term that is widely abused when people talk about 'heat-treat distortion.'" In point of fact, he explains, the steel blank begins in one phase, and through cutting and heat treating, there are phase changes. So far as he is concerned, "Heat-treat changes are part of the fnal geometry." This ties in with the issue of determining the purpose of the gear and the size of the purse that's available for processing and equipment. Wade explains, "If you want the ultimate in accuracy, fnish the treat after heat treating." Grind them. But that's expensive. So an alternative, he says, is to determine the effects of heat treating on the gear as machined, and then design the "green," or non-heat-treated gear so that heat-treat changes are intentional. Warns reveals what he calls "the big secret" about gears: You have to have design and manufacturing working together. Why? September 2013—11

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