Gear Production

SEP 2016

Gear Production

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September 2016—7 tools enable operators to cut at higher strokes per minute and to run modified programs to minimize cycles. The cutting tools hold an edge much longer than they once did thanks to stronger materials and newly developed coatings. Still, shaping is a slower process than hobbing, requiring creative ways of getting as many gears as possible across the machine. The solution, due to the limits of the process technology, involves training an operator to run multiple machines. With a total of eight shapers on hand in South Bend, Schafer has worked to train a single operator to oversee five or six running machines. The slightly slower cycle times are what make it possible for one operator to load and unload so many machines at once. Shaving—Whereas shaping is a roughing operation, gear shaving is a finishing process that corrects errors in index, helical angle, tooth profile and eccentricity. It can remove the majority of the errors often found in hobbed or shaped gears. As its name implies, in shaving, the cutting tool rides across a gear's surface and between its teeth to continuously remove tiny shavings of metal, providing a smooth surface finish and therefore quieter gear sets. The process also increases a gear's load-carrying capacity as well as its service life, since a smooth surface protects the gear from spalling, and wear between mated parts is minimized. The cutting tool used in rotary gear shaving operations is made of high-speed steels, hardened and ground. Factors affecting tool life include the condition of the parts coming off the hobber. Some shaving cutters can process as many as 4,000 gears between sharpenings, and they are generally resharpened about 10 times. Remembering a time not that long ago when shavers were relatively rudimentary, Mr. Fussell says new CNC shavers show improvements both in their ease of use and their machining capabilities. Progressive diagonal cutting is another helpful process, which takes the approach of moving the cutter across the gear tooth, providing the operator with more versatility to make profile adjustments. Continued Improvement After a season of heavy investments, both in terms of capital equipment and business acquisitions, Schafer Gear Works plans to continue streamlining operations and learning about the latest technologies that will enable them to continue to prosper, add capabilities and enter new markets. According to Mr. Blenke, the company is generally making its strategic plans quite a few years in advance so they'll be prepared for upcoming changes. Many of them have to do with investing in connectivity—a few of their Gleason machine tools are connected to the OEM's service technicians at present, and Schafer's impression of the technology is highly favorable—improving quality control, as it recently did by purchasing a Gleason 300GMS P gear inspection system; and cross-training employees for a flexible and agile workforce. The large gear in this helical assembly is made of ductile iron, and the small gear is made of hardened 8620 steel. The finished small gear is pressed into a large gear blank, and then large gear teeth are cut by hobbing and then finished by shaving.

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