Abstract
In the first report, the author had succeeded in recording simultaneously the rotational error of both the worktable and the hob shaft and the cause of both rotational errors was inferred by examining their power spectra. Also, it was ascertained that a qualitative coincidence existed between the tooth profile estimated by the relative rotational error measured and the test result of the tooth profile generated by the machine. In the case of a common hobbing machine, the torsional rigidity of the driving system is not sufficient in its construction. Being considered that this insufficiency of the torsional rigidity may cause the rotational error, the experiment was carried out, by employing the already reported hobbing machine, on the torsional excitation of the hob shaft in not-driving situation and the impulse response was examined by hammering the driving worktable in the counter-rotational direction. By comparison of the torsional dynamic digidity obtained with both rotational errors in the previous report, the rotational erroneous components caused by the insufficiency of this rigidity were revealed. Additionally, the cause of the rotational erroneous component which induced the large error of the tooth profile was investigated.
