Mitsubishi Heavy Industries Ltd. has identified a growing worldwide demand for high-precision, large-size gears for machinery like wind turbines; rolling mills and other large-scale installations used in steel and aluminum production; agriculture construction machines; and other oversized designs — and it’s introducing a line of machine tools to produce those gears.
Potential suppliers of those large-size gears need high-efficiency, high-precision, and cost-effective heavy-duty machinery - specifically, hobbing, shaping and grinding machines for processing gears with diameters larger than 1,000 mm.
In response, MHI has introduced GEA1200 gear hobbing machine and the ZGA2000 gear grinding machine. The company indicates it plans to develop and introduce machines for processing workpieces with maximum diameters of 1,200 and 1,600 mm, and to introduce machines for internally toothed ring gears, too.
Also, MHI indicated it plans to introduce gear-shaping machines that can accommodate workpieces with diameters up to 2,000 mm. In line with that, it says it will establish a new business model encompassing after-sale services, maintenance and tool supply, primarily for large-size gear machines.
Large Gear Hobbing
MHI’s GEA Series of gear hobbing machines are a new development capable of processing large-size workpieces that exceed 1 meter in diameter. Equipped with a highly rigid hob head and rotating table, the GEA1200 can perform highly efficient, high-precision machining of gears up to 1,200 millimeters in diameter.
The GEA1200 hobbing machine comes equipped with a 30-kW main motor (a 60-kW option) is available also, and a 1,200-mm diameter hydrostatic bearing table capable of bearing superimposed loads up to 15 metric tons. The large-size hob, with maximum diameter of 350 mm (optional up to 500 mm), rotates at a speed of 25-250 revolutions per minute and cuts gears up to 20 modules — the unit used to indicate gear size; up to 30 module cutting is — on the workpieces. The GEA1200 can reduce machining time by about 30%, according to MHI, compared to existing hobbing machines of this size. It has been certified to the JIS7 (Japanese Industrial Standards) class machining precision.
The GEA Series is part of the Mitsubishi E Series machines, designed for global energy saving and operability standards. Machines in the E Series, which includes hobbing, shaping and gear grinding machines, all feature the same concept in order to facilitate the creation of production lines combining these machines. Many energy-saving features are standard, noise reduction and environmental friendliness have been maximized, and operability and maintenance ease have been enhanced.
Large Gear Grinding
Following the introduction of the GEA1200 hobbing machine, Mitsubishi Heavy Industries Ltd. introduced a new large gear grinding machine in Japan. The "ZGA2000" is capable of machining external gears of workpieces up to 2 meters in diameter, with high speed and high precision, and MHI contends the system “will significantly reduce idle time and boost operability, enabling gear manufacturers to increase their productivity.” It intends to promote the new machine for use in producing large-size gears for wind turbines and iron and steel production machinery.
The ZGA2000 gear-grinding machine is equipped with a direct drive (DD), motor-driven turning table that will hold workpieces of up to 20 tons. DD technology is also used in the machine's grinding wheel spindle and dressing systems, which restore the correct grinding wheel profile for high efficiency and accuracy.
It can machine up to 36 modules, and is available in three types - with grinding wheel vertical strokes of 700 (standard), 1,400, and 1,800 millimeters. The final selection depends on customers' machining needs, such as gear face width, the length of the workpieces and the location of the gear in the workpieces, according to the machine’s designer.
The ZGA2000 system is provided with a new software control system, with functions such as high-speed, high-precision gear measurement; eccentricity compensation that measures errors of work piece positioning on the table and sends this data back to achieve proper machining; and optimization of the machining process by estimating grinding stock of all teeth based on automatic stock dividing data. With these features, the ZGA2000 enables reduced idle time and enhanced operability.
In addition to the gear hobbing and grinding machines, MHI indicatesd it plans to introduce gear shaping machines that can accommodate workpieces with diameters up to 2,000 mm. In line with that, it says it will establish a new business model encompassing after-sale services, maintenance and tool supply, primarily for large-size gear machines.