New Liebherr CBN grinding discs are small but powerful

25 millimeters – the size of a two-Euro coin – is the diameter of the new CBN grinding discs developed by Liebherr-Verzahntechnik GmbH specifically for machining critical component geometries with low tool overrun. (Courtesy: Liebherr)

Alongside diamond, CBN (cubic crystalline boron nitride) is one of the hardest grinding materials available. CBN grinding discs are suitable for the highest quality requirements because they are dressing-free, wear-resistant, and heat-resistant. Liebherr has developed very small CBN grinding discs with a diameter of just 25 millimeters for gears subject to collision and with low tool overrun.

The company is therefore extending the geometric process limits for internal and external gears with interfering contours.

CBN grinding discs have a steel body, which is electro-plated with abrasive CBN grains. The basic steel body is break-resistant and can be reused several times. However, the manufacturing process is complex, especially when making very small discs. With more than 30 years of CBN expertise, Liebherr has the necessary know-how to manufacture the grinding discs completely in-house.

The smaller the discs, the more complicated they are to manufacture.

“In this size range, the process has no margin for error,” said Haider Arroum, head of sales for gear cutting tools at Liebherr. “And you also have to choose the right grain size to achieve the desired surface roughness of the workpiece while generating as little wear as possible, even at high rotary and cutting speeds.” Liebherr’s special design allows for shorter and more economical grinding processes.

The tiny discs are already being successfully used by Liebherr-Aerospace for profile grinding of small gears for planetary gear trains.

“They’re very happy with the results. And, as expected, both the quality and the cost-effectiveness were excellent — an important factor in this area in particular,” Arroum said.