Development of a stability intelligent control system for turning

This paper presents a stability control system based on a new strategy, with application in turning. It works by permanent assessment of the system operating point position relative to the stability limit, and process parameter permanent, in-process modification such as this point is always placed in the stable domain zone that gives the highest process performance. In the case of turning, here approached: (1) this zone is the stability limit proximity; (2) the system operating point position is determined by assessing a cutting force monitored signal feature; and (3) this position is changed by modifying the cutting edge setting angle, the feed rate, and the cutting speed, as it follows: when the risk of overpassing the stability limit is imminent, the setting angle is increased, followed by a feed rate diminishing and then by a worked piece rotation speed reduction, while immediately after surpassing the risk, the three variables modification is reversed, this way the chatter onset being permanently avoided and the performance kept in every moment at the highest possible level. The system was experimentally implemented on a transversal lathe. The results of tests on dedicatedly designed specimens are showing a machining productivity significant increase, in conditions of a stable cutting process. The system is simple, and it can be easily added to the existing CNC machine tools, without important modifications.