Abstract
A new technique was developed for the investigation of chatter formation considering the instability of the closed-loop system formed by machine tool structure and metal-cutting process. Machine tool structure indicates the importance of different system components and it's dominating mode frequencies whereas the metal cutting process indicates the effect of the instability of chip formation-chip serration frequency. The mechanisms of the investigation of chatter explained by the technique were experimentally verified during end milling operation of medium carbon steel (AISI 45) considering the chips and types of discreteness in the form of serrated saw teeth. Experimental investigations have been conducted on the chips and common types of discreteness in the form of serrated saw teeth. Mechanism of formation of these teeth has been studied and the frequency of their formation has been determined. The different modes of the vibrating components of the machine tools have been identified using modal analysis and the vibration responses during cutting conditions have been recorded using an online monitoring system. The vibration signals in frequency domain have been analyzed to identify the chatter frequencies and compared with the chip serration frequency in a wide cutting speed range for different cutting conditions. It has been found that chatter is the outcome of resonance, which occurs in the system when the frequency of secondary or primary serrated teeth formation is approximately equal to or an integer multiple of the 'prominent mode frequencies' of the system components.