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Development and application of large gear processing technology

Processing can be used from the large gear hobbing grinding to a variety of technology. Since hobbing typically have higher productivity , thus hobbing applications in production are more extensive than any other large gear processing methods.

Currently , prompting large gear cutting to improve the efficiency and accuracy of the technology trends include :

( 1 ) gear cutting tool technology ( in particular, the coating and substrate technology ) progress.

( 2 ) optimization of gear cutting tools to explore design.

( 3 ) a higher degree of flexibility gear cutting machine tools or machining operations can be done more in one clamping .

When the large gear manufacturers strive to meet the production capacity and the stringent precision requirements , the question has become : "The future of large gear cutting machine can achieve accuracy and repeatability how high ? "

With advances in tool coating and substrate , dry cutting trend continues to flourish as a large gear processing industry , without the use of coolant conditions , improved cutting speeds , longer tool life. Currently , dry cutting technology has become the standard bevel gear machining ; while processing large parallel shaft gear cylinder is gradually turning dry cutting .

Carbide blade bevel gear cutting tools used by coating a thin hard coating greatly improves tool life . According to TJ Maiuri Gleason (Gleason Corp.) Application engineering manager , TiAlN coating use is still quite common. Meanwhile , non- Ti elements AlCrN coating has become an optional coating. Oerlikon Balzers by the company (Oerlikon Balzers AG) developed under the trade name "Balinit Alcrona" The AlCrN coating hardness up HV0.053200, the friction coefficient of 0.35 , and most importantly, its maximum operating temperature up to 1100 ℃.

More surfaces of the tool can also be coated to improve the tool life. Gleason 's Maiuri explained strip inserts for machining bevel gear is usually only rake face coated. In the other case, if the blade surfaces ( top and sides ) is also used coating , you can not insert or in any other process conditions change so that the tool life increased by 50% next .

Hob forming method for cutting parallel shaft gear and bevel gear cutter for cutting different , they are usually multiple rows of teeth on its cylinder , similar to the shape of the worm . This is usually a high-speed steel hob (not carbide ) as the base material , and the use of advanced coating. Many manufacturers use the hob as a powder metallurgy high speed steel tool material , while others insist manufacturers use more traditional matrix material .

As an example of the cutting tool technology advances parallel shaft gear , Mitsubishi Heavy machine Superdry branch launched its new version of a large gear hobs products . According to Ian Shearing , vice president of Mitsubishi Heavy Industries introduced the hob uses is called " Mitsubishi Mach 7" high-speed steel substrate and "Mitsubishi Superdry" special coating. Mach 7 is a simple matrix , high-speed steel alloy ( not Powder HSS ) . "Mach 7 malleable , able to withstand high chip load ," Shearing said, " When the dry hobbing, it is very necessary, because the larger chips can be cut heat away from the work area. Moreover with Mach 7 as the base material to avoid chipping tool problems, and high alloy content of powder metallurgy high speed tool steel substrate is sometimes the case chipping will happen . Mach 7 will appear first before chipping crater wear , and this situation with better predictability . "Superdry coat two versions . Superdry 1 coatings for cutting speed 200m/min following hobbing machining ; while Superdry 2 matrix coating for Mach 7 , the same cutting speed processing of large gear up 250m/min.

Superdry 2 coating is essentially a AlCrN coating , Mitsubishi has applied for a patent for additional components .

By optimizing gear geometry tool can improve tool life and large gear processing efficiency. Compared with the tool life and to improve processing efficiency by increasing or switch to a more robust tool coating matrix tool , tool geometry optimization is a cheaper way . Alexander Klein of the University of Aachen in Germany is not the idea of how the tool itself becomes tougher , but how to make chips for bevel gear milling strip blade surface damage smaller. In the study of the formation mechanism of the chip , Klein designed a chip from the tool can cut shapes out of the uniform . He developed a way to simulate bevel gear hobbing process surface experiments can be studied different tool design, tool and the ability to observe the formation of harmless chip . His research shows that using the new design of the blade strip , with the old and new K10F carbide ( the use of TiAlN coating ) as compared to the design , the tool life can be increased to 115% . Klein said the company has a patent for the Gleason research results , and may soon be his tool design solutions for commercial product development. "Although better tool wear performance is not entirely dependent on a better chip flow ," Klein explains, " but to improve chip flow of parts can be reduced at least an arc at the tip ( tip and the plane between the cutting edge ) thermal and mechanical loading . "

Large gear cutting machine tools have become more multi-functional, the installation can be completed through a variety of processing operations. For example , the German company Liebherr and LMT-Fette cooperation, fine rolling process has been improved in the first installation , only to have completed the hob with a rough cut of the workpiece gear , precision cutting and chamfering .

Due to the current hobbing not allow automatic tool change , it is often the quality hob completed using the same rolling process in fine rough cut and fine cut, the tool is easy to premature wear. In order to extend tool life in tool design , the area can be rough cut and fine cut to separate and wear properties were optimized for each zone . According to Darryl Witte Business Manager LMT-Fette Group companies and large gear cutting , due to the fine hob now no longer starts from the rough Qiejia wear , thus increasing the number of times the processed workpiece. Liebherr and LMT-Fette companies to develop this concept hobbing , provided by Liebherr companies can use the multi-zone hob hobbing technology.

The two companies in the same development team also invented a patented fine hob tooth , it can eliminate toothed spiral shape to repair large gear convex error ( called " distortion" ) . Typically , in order to eliminate this distortion, but also requires additional honing such as shaving or after the sequence , such as finishing . No- distortion (twist-free) fine roll it means that it is possible to cancel the order after finishing .

"Twist-free technology enables the hob to overcome the typical precision hobbing defects , but it can not achieve the required flank modification ." Liebherr 's Oliver Winkel said. Increase in such a chamfering tool system , you can install the same process that provides more value and before removing the workpiece from the hobbing machine deburring .

"In the past few years, we have made in improving processing performance aspects of gear cutting tools significant progress , and constantly improve the durability of the tool , a hob need resharpening before 8000 can generally be processed workpiece , while the previous hob processing 100 to 200 per piece on the need to re- grind . "Tom Ware Star SU ( on behalf of large gear cutting and Star Cutter manufacturer Samputensili a company ) of gear cutting tools product manager , said , " Today 's gear hobbing up to 450m/min processing speed , and now hobbing accuracy can reach 5 to 10 years ago, precision grinding of teeth . "

Ware said hobbing桑普坦斯利(Samputensili) companies now offer a variety of processing to be completed in the first installation , for example, in addition to teeth processing , but also can complete a simple slot deburring turning . This additional functionality can be added to any one of the company's CNC hobbing桑普坦斯利. Star SU also offers a patented composite tool , the tool can be completed with the same hobbing and chamfering .