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ADVANCED MANUFACTURING NOW Scott Knoy


Hard Scudding Shapes New Horizons in Gear Production and Performance


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ust a few years ago, the concept of Scudding left the traditional skiving method in the dust, so to speak, for internal gear production used primarily in the powertrain buildup. This process, 5-10 times faster than gear shaping, formed the surface of the workpiece through several, small enveloping cuts, providing a surface fi nish and part quality level that was far superior to hobbing, shaping or broaching. Scudding is a continuous generating process, meaning


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no idle strokes on the machine tool, as when shaping gears. Ring gears, sliding sleeves and annulus gearing, whether internal helical or spur, external helical or spur or blind spline, synchronizer parts with block tooth features and synchronizer hubs remain among the popular products in the market, made with Scudding technology. Today, this continuous gear cutting process is widely


used in production environments for internal, external, helical and spur gears, as well as splines and other components in the powertrain world. The machining can be done without the need for an undercut or groove (clearance) and lead of the gear can be manipulated via axial motions (crown/taper). It is a demonstrably superior technology and automotive sup- pliers have embraced its advantages for many years now. Impressive a technology as it is, the industry took another step forward recently with a new process known as hard scudding. The conventional scudding process provides excellent results on green or soft gears, while this new ad- vancement enables the re-machining of hardened gears with a tooth-to-tooth composite error and total composite error in the AGMA 12, DIN 5 range and a surface fi nish better than 1.5 Ra.


The capital investment is minimal for shops and produc- tion departments already doing scudding, because the same gear can be run on the same CNC machine, using a solid carbide tool to do the work. Recent testing done on various internal automotive powertrain and agricultural machinery ring gears is showing extremely positive results.


18 AdvancedManufacturing.org | September 2015 Stock division calculations on the tooth position are


standard technology for GMTA and Profi lator, so re-cutting is quick and easy. Using the latest CNC technology to control the machine kinematics, users are able to transfer this technology to scudding machinery that is already deployed in the fi eld. Thus, the same part can be cut on different machines at different times, allowing for more fl exibility in scheduling.


An automotive ring gear that requires 40–50 seconds for scudding can be hard scudded in 25–30 seconds.


With today’s portable programming, onscreen or offl ine tool path and cutting condition simulation, plus the im- mediacy of call-up onscreen for all values and tolerances in real time, the busy machine shop or large production department stays fl exible and demand responsive, using this hard scudding technology. In some cases, this new technology is applicable on near net, pre-hardened gear blanks, allowing signifi cant step reductions in the manufac- turing process.


In operation, cutting 60-100 thousandths per fl ank on a tooth, the hard scudding process can be used on a carbu- rized or through-hardened parts; nitriding generally does not provide enough case depth to ensure suffi cient stock for “clean-up”. An automotive ring gear, for example, which requires 40-50 seconds for scudding can be hard scudded in 25-30 seconds. This process development stands as a viable and cost-


effective alternative to conventional grind-and-hone opera- tions, yielding a highly attractive cost per piece and extended tool life. The added benefi ts of reduced capital outlay and a signifi cantly more consistent end product bode well for the automotive powertrain and other gear market segments.


Vice President of Sales & Marketing German Machine Tools of America www.gmtamerica.com


MODERN MANUFACTURING PROCESSES, SOLUTIONS & STRATEGIES


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