Improvements in Centreless Grinding Machine Design

Abstract

In order to investigate the effects of a high mount frequency and the stiffness requirements in the centreless grinding process, a now research oriented machine tool has been designed and developed. Compared with a conventional machine of comparable size it has a very much higher static stiffness and a first resonant frequency of 500 Hz. The grinding results suggest that future centreless grinding machines should be designed to achieve a high first resonant frequency to minimise forced vibrations. However, for some grinding operations it may be beneficial to continue to utilise a compliant rubber bonded control wheel to provide adequate static compliance and hence avoid exaggeration of the geometric regenerative effect. A combination of a moderate degree of static compliance and a high first resonant frequency was found to jive the best overall results. It was also shown that there is an optimal range of rotational work-speeds for minimum roundness errors. This range was related to the grinding wheel rotational speed by the ratio Ng/Hw. The optimal speed ratio range for the new stiff machine was 2 to 13 whereas for a conventional machine the range was 6 to 9 for otherwise similar grinding conditions.