The evaluation of low-frequency knock in the gearbox of modern machine tools

Abstract

It is well-known that the manufacturing quality of a gearbox is bound to be reflected in the intensity of low-frequency knock of its gear pairs running under light load condition. Nowadays, in machine tool industry, it is checked in receptional inspection through aural comparison, which completely depends upon the subjective experience of skilled masters without any theoretical background. In this paper, a systematic experimental research in order to explore the nature of this aural inspection is reported. A scientific and objective criterion called the sensitivity of low-frequency knock (SLFK), is suggested to characterize the recognition capability of the low-frequency knock in the background noise of gearbox by human ear. By means of comparison the SLFK values measured with the results of the aural inspection for one type of lathe headstocks, it is confirmed that the subjectivity of the latter, for example, the influence of environment noise, the sentiments and attention of the inspection personnel, etc. and thus the inappropriate judgements are unavoidable. Furthermore, the authors also attempt to evaluate the synthetic quality of above headstocks by means of this new criterion, the values of which are relatively objective, comparable and understandable.