Improving Gear Hobbing Machine Drive Systems by Computer-Aided Design Part II: Analysis of Torsional Vibration in Bobbing of Large Gears

Summary

A new method for computing the torsional static and dynamic characteristics of complex rotational transmission mechanism is applied to analyze torsional vibrations in the rotational transmission mechanism of a mid-size gear hobbing machine ( maximum workpiece diameter: 1.5 m ) on which violent self-excited chattering occurred, and of a large size gear hobbing machine (7.0 m) on which chattering did not occur but for which vibration analysis was performed experimentally by means of a spectrum analyzer. Consideration of experimental results along with the results of computational analysis not only isolates the cause of the violent self-excited chattering but also suggests specific design improvements based on the distributions of potential, kinetic and damping energies, and the mode shape calculated for the natural frequency causing the trouble. The effect of such design improvements can be proven by computation or by testing performed on actual machines. Experimental and calculated results form the basis for proposing optimum gear cutting conditions for large size gear hobbing machines.