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New Technology for Internal Gear Tooth Profile Grinding

Dressable Cubitron II profile grinding disk

Electroplated CBN triple disk set manufactured by Liebherr

Liebherr offers new internal gear tooth profile grinding technology based on its OPAL grinding technology. It involves a belt drive spindle that can be fitted to the standard GH 4.0 grinding head as well as to the new GH 5.0 and GH 6.0 grinding heads. Initially, the internal gear grinding arm is available in two different sizes, with others soon to follow. Custom internal gear grinding arms can be developed to match customer workpieces.

"Gear grinding to Liebherr quality standards is feasible for internal gears using a range of different grinding arms that each fit the GH 4.0, GH 5.0 and GH 6.0 grinding heads," said a company spokesperson.

"Simple changeover between external and internal gears takes a maximum of half an hour," said Dr. Hansjörg Geiser, head of Gear Cutting Machinery Development and Design Engineering. "Detach the external gear grinding disk or worm, hang the internal gear grinding arm on the hardened stop bars to ensure repeat accuracy and fix it in place with a handful of screws, then tension the belt-drive disk and belt and attach the cover."

Internal gears can be ground using a grinding disk of 100 or 125 mm in diameter. The external gear grinding head does not have to be touched, and external gear grinding quality is again the same as before once the internal gear grinding arm has been detached.

IG Opal 4.0 functions at a maximum spindle speed of 12,000 RPM. A larger version, the IG Opal 4.1 featuring a maximum grinding disk diameter of 125 mm, is also available. Both arms were successfully tested using CBN and corundum disks. Where dressable grinding disks are used, the internal gear grinding arm travels up to the grinding dresser that is also used for external gear grinding.

All internal gear grinding arms are modeled in 3-D and can be used in confined spaces. "Collision inspections are simple and reliable," said Andreas Mehr, who is responsible for grinding and shaping technology development and consultancy at Liebherr-Verzahntechnik GmbH. "Small diameter internal gear teeth can therefore also be machined quickly and easily."

Liebherr-Aerospace, which uses Liebherr gear cutting machinery to manufacture its own components, was one of the first buyers of this new technology. As in the case of external gears, this new internal gear teeth technology works with a multi-rib grinding disk system that can rough and finish ground. That is particularly important to users who regard speed and costs as important, for instance customers from the aerospace industry. Grinding disks made of dressable corundum or electroplated CBN can be used in conjunction with the spindle. These are also manufactured at Liebherr's plant in Ettlingen, Germany.

For more information contact:

Liebherr Gear Technology, Inc.

1465 Woodland Drive

Saline, MI 48176-1259


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