A Study of the Monitoring and Suppression System for Turning Slender Workpieces

Abstract

The main purpose of this study is to develop a chatter monitoring and suppression system while turning slender workpieces. In order to clarify the chatter behaviour, the ratio of the length to diameter of the cylindrical bar (L/D ratio) is considered as an independent parameter. Experimental investigations were carried out over a wide range of the L/D ratio and cutting conditions to identify the cutting stability. It can be observed that the standard deviation value of the main cutting force obviously increases in the chatter developing period, and this phenomenon can be used to define the chatter threshold. From the observation on the variation of the standard deviation value of the cutting process and then by means of a reasonable application of the standard deviation value, a precise on-line chatter threshold based on the double-standard concept has been defined in this paper. For an accurate judgement of the chatter occurrence, an effective monitoring criterion was proposed and developed. This monitoring criterion was applied to the feed rate control system to suppress the chatter vibration by increasing the feed rate. Experimental results show, furthermore, that the control system is effective when the L/D ratio is smaller than 12.