MHI Develops World's First Technology Enabling One Grinding Machine
To Perform High-speed, High-Precision Machining of Diverse Gear Types:
Internally Toothed, Externally Toothed and Stepped
-- Also Realizes Low-cost Processing through to Finishing --
Tokyo, December 8, 2011-Mitsubishi Heavy Industries, Ltd. (MHI) has developed technology enabling high-speed and high-precision machining of a diverse range of precision gears, which are used in vehicle transmission systems and other applications, by a single machine, thereby permitting the complete grinding process, through to finishing, to be achieved at low cost. By applying two different multi-threaded grinding wheels according to the specific machining task - a proprietary technology - the company's innovative new system enables mass production of gears requiring difficult machining, including internal ring gears as well as some external gears such as stepped gears and pinion gears with shafts. Through aggressive proposal-based marketing, the company looks to capture expanding global demand for quieter gears and for more compact and lighter gear mechanisms.
MHI developed its new grinding technology aiming to significantly expand the application fields of the company's "ZI20A," an epoch-making high-performance grinding machine for internal ring gears introduced in 2009. To realize external gear machining by the ZI20A, the company adopted an hourglass-shaped* multi-threaded grinding wheel that was developed specifically for this purpose. Stepped gears, which have gears of different diameters layered in a staircase pattern, and pinion gears with shafts are machinable thanks to the prevention of interference between grinding wheels and workpieces.
For grinding of internal ring gears, which are typically used as planetary gears, the machine conversely uses a barrel-shaped* multi-threaded grinding wheel. The grinding wheel enables high-speed and high-precision finish machining by preventing possible interference between the grinding wheel and the workpiece, as in the grinding of external gears.
For finish grinding of internal ring gears, external stepped gears and gears with shafts after heat processing, conventionally a method for grinding tooth grooves one by one using a small-diameter disk-shaped grinding wheel has mainly been used to prevent interference - a procedure that erodes mass production merits and impedes cost reduction efforts. In contrast, in lieu of a disk-shaped grinding wheel the ZI20A uses a multi-threaded grinding wheel capable of multi-tooth groove grinding simultaneously. Featuring a high rotation speed of 15,000 revolutions per minutes (rpm) for the main spindle and 6,000 rpm for the workpiece spindle, the ZI20A enables a 75% reduction in grinding time compared with conventional machines, while still maintaining high accuracy. MHI has already received orders for two units of the ZI20A incorporating the new technology; deliveries are scheduled for completion before year's end.
MHI entered the gear cutting machine business in March 1962 with a gear hobbing machine featuring technology from Germany. In its 50 years of operation in this field, the company has consistently led the industry with diverse gear cutting machines and cutting tools offering high performance and accuracy while simultaneously addressing global environmental issues, and in the process MHI has established one of the world's top positions in terms of delivery track record. In 1999 the company's dry cutting gear production system - the first of its kind to use no cutting fluid - was awarded a prize by the (then) Ministry of International Trade and Industry for its excellent contribution to energy-saving machining.
The technology enabling high-accuracy, high-speed finishing of various types of gears by the ZI20A gear grinding machine is an example of the company's commitment to continuously accommodate newly arising customer needs through application of its accumulated technologies. The system also well represents the company's strategy for its gear cutting machine business, which calls for MHI to promote differentiation of its gear cutting machines as high-performance, high-end systems amid rising competition from inexpensive machines for rough processing available from manufacturers in the emerging economies.
Going forward MHI will further refine its technologies to satisfy increasing customer demand for even faster and more precise finish processing and for machining of thin or complexly shaped gears, in response to moves toward quieter, more compact and lighter gear systems.
Note: In an hourglass-shaped multi-threaded grinding wheel, the diameter gradually decreases from both ends toward the center; in a barrel-shaped wheel, the diameter expands toward the center.
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