Get groning: General Industry Coverage

What do you get when fusing grinding and honing? “Groning,” according to Italian machine tool builder Stabilimento Industriale Costruzione Macchinario Attrezzature Torino SpA. “Our philosophy is to use a cutting speed, whenever possible, between that of grinding and honing,” said SICMAT’s Technical Director Alberto Miletto Petrazzini. “The speed is lower than that used for grinding to avoid surface burns and cracks and higher than that used for honing to reduce the contact pressure between the workpiece and the wheel, so the structure is less stressed and the wheel works at a more favorable speed.”

He added that the ideal cutting speed for groning is from 14 to 22 m/sec., compared to a typical speed of 8 m/sec. for honing and at least 30 m/sec. for grinding.

To achieve that capability, SICMAT developed the Grono 250 CNC gear honing machine and conducted research in collaboration with the engineering faculty at Turin Polytechnic University to prove the machine tool’s practicality. The machine applies a unique honing wheel with external teeth to increase cutting speed while reducing costs, according to Petrazzini. (Traditionally, gear honing is performed using wheels with internal teeth, which are reportedly expensive and time-consuming to set up.)

Courtesy of NUM

SICMAT’s Grono 250 CNC gear honing machine uses a unique honing wheel with external teeth.

“We can increase the cross-axis angle between the workpiece and the wheel up to 60° thanks to the external teeth versus 20° maximum for wheels with internal teeth,” he said. If that’s not possible, users can boost the cutting speed by increasing workpiece spindle speed to 7,000 rpm, with 10,000 rpm planned for the future, Petrazzini added.