GMN Introduces High-Speed Spindles for Improved Machining

Spindle manufacturer GMN reports that greater cutting depths, higher material-removal rates and finer surface quality when roughing, finishing and grinding can be obtained with its new range of high-speed spindles.

Standard spindles undergoing high machining forces often lead to “rattling,” caused by insufficient damping of natural vibrations, according to Bernd Möller, head of spindle development at GMN Paul Müller Industrie GmbH & Co. KG, Nuremberg, Germany. These vibrations have serious consequences, including the creation of rough, partly scratched surfaces, uneven cutting tool edges and even spindle failure. “Our analysis was showing that there is a good chance to improve the dynamic behavior by introducing more damping into the spindle with the help of a hydraulic system,” he said.

Hydroviscous damping systems are structurally identical to standard models and can be easily retrofitted to existing machines. Image courtesy GMN.

Studies conducted in cooperation with the Laboratory of Machine Tools and Production Engineering (WZL) at the Rhine-Westphalia Institute of Technology Aachen determined it was possible to double the minimum stable cutting depth at speeds from 10,000 to 18,000 rpm with GMN’s HCS 280 high-speed spindle.

In practice, it is almost impossible to select optimal speeds for cutting from a stability chart. Even at slower speeds, Möller said that hydroviscous damping offers good surface results up to a plunge depth of 6mm (0.236 “). A depth of only 3mm (0.118 “) was achieved using a standard spindle under the same conditions. Surface quality also improved for internal cylindrical grinding and surface grinding when performed with a hydroviscously damped spindle, producing a roughness of 0.89µm compared to 2.36µm using a standard model.