Modern Machine Shop

JAN 2017

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mmsonline.com January 2017 MMS 79 FEATURE I n some cases, an improvement to a machining process or the addition of a new machining c a p a b i l i t y l e ad s to i m p rove m e nts i n a n e n d product's performance. The latter has been the experience at the Siemens Large Drives motor p l a n t i n t h e p r o d u c t i o n of i t s A b ove N E M A horizontal AC induction motors that range to 18,000 horsepower. This successful line of motors is produced at the company's 119-year-old Norwood manufac- turing facility in Cincinnati, Ohio. The motors are used in various industries such as mining, chem- ical, power generation, pulp and paper, and oil and gas. One key motor component is the rotor shaft that installs a stator. Antonio Lassandro, Siemens Norwood's senior manufacturing engi- neer, says rotors for these motors range from 5 to 13 feet long and have diameters from 8.5 to 20 inches. Made from steel forgings, these rotors (which the team there has nicknamed "logs") can Turn-Mill Technology Improves Industrial Motor Performance By replacing a welding process to create rotor cooling channels with multi- tasking machining from a solid forging, Siemens Norwood in Ohio has realized improved induction motor vibration qualities and much faster overall rotor production times. BY D E R E K KO R N Turn-mill technology enables the Siemens Norwood facility in Cincinnati, Ohio, to more effectively manu- facture rotors like this for its large Above NEMA AC induction motors. weigh as much as 6,000 pounds. A number of machining operations are required to produce a finished rotor from a shaft forging, including rough and finish turning; milling, drilling and tapping; as well as cylindrical grinding and hand diamond burnishing of key surfaces. Stress relieving of rotor shafts and final rotor-assembly- balancing operations are also performed. Although all of these operations are still required today, it's now possible for Siemens Norwood to complete all the machining work on one multitask- ing machine in only two setups, rather than send- ing workpieces across various pieces of equipment, such as lathes and horizontal mills, as it once did. Just as importantly, a manual welding process was eliminated that not only greatly reduced rotor manufacturing time, but improved the vibration characteristics of the company's motors. "FLUTING," NOT WELDING In order to cool a stator during motor operation, the section of the rotor inside the stator includes a number of straight, longitudinal channels that serve to direct air through and out of the stator. Ini ti a ll y, S i e m e ns N o r wo o d we ld e d mul tip l e

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