Development of generalized tool life model for constant and variable speed turning

In this research, a generalized tool life modelling for considering non-stationary cutting conditions was developed . In particular, for the first time in literature, the model was conceived for predicting the life of the tool when spindle speed variation SSV, one of the most effective techniques for suppressing regenerative chatter vibrations, is used. The proposed formulation takes into account the main cutting parameters and the parameters associated to the SSV. A dedicated experimental campaign of turning tests was executed and the data were used for modelling purposes. The model validation was carried out performing additional tool life tests. According to the analyzed technological scenario, it was found that the generalized formulation can be used for predicting the tool life both at constant spindle machining CSM and adopting SSV with the maximum estimating error of 6%.

Tool Life Modelling In Continuous Variable Speed Turning

In this paper, a generalized tool life model that considers nonstationary cutting was developed. In particular, the model was conceived for predicting the life of the tool when Spindle Speed Variation SSV , one of the most effective techniques for suppressing regenerative chatter vibrations, is used. The proposed formulation takes into account the main cutting parameters and the parameters associated to the SSV . A dedicated experimental campaign of turning tests was carried out and the data were used to develop the model. A proper validation was even carried out performing additional tool life tests. It was found that the generalized formulation can be used for predicting the tool life both at constant spindle machining CSM and adopting SSV within the maximum estimating error of 6%.

Investigation of Correlation Between Process Energy Balance and Phase Shift Variation of Chatter Vibration in Spindle Speed Variation

It is widely known that the spindle speed variation (SSV) is an effective technology for chatter suppression, especially in the turning or boring process. Its simple optimal design, however, is not a simple task. In the past, certain research works considered the chatter onset from the perspective of process energy balance in a vibration cycle. The phase shift between previous (i.e., outer modulation) and present vibrations (i.e., inner modulation) of chatter is a key factor in the process energy balance. The SSV can be conceptually interpreted as a technique that continuously perturbs the phase shift between the inner and outer modulations, thereby changing the process energy balance. Simply put, the chatter energy can be controlled by applying the SSV to suppress the chatter. This study investigates the correlation between the process energy balance and phase shift behavior in the sinusoidal SSV through numerical energy simulation. The results indicate that the phase shift at the maximum spindle speed is an important factor to minimize the total energy balance (i.e., to dissipate the chatter energy) in the SSV cycle. This probably corresponds to the fact that the beat vibration tends to occur near the maximum spindle speed in the SSV. The insights gained from this study are anticipated to serve as a guideline for shaping the phase shift profile in the SSV to effectively suppress chatter vibration.

Active Chatter Suppression in Turning by Simultaneous Adjustment of Amplitude and Frequency of Spindle Speed Variation

In machining processes, chatter suppression is very important for achieving a high material removal rate, good dimensional accuracy, and surface finish. With the merits of effectiveness and easy implementation, spindle speed variation (SSV) is regarded as a promising approach for chatter suppression. However, there is little research on the selection of SSV parameters for adaptive chatter suppression. Although the effectiveness of adaptively adjusting SSV amplitudes has been recently examined, the simultaneous adjustment of the SSV amplitude and frequency is expected to exhibit stronger adaptability since it achieves greater flexibility. In this paper, an active chatter suppression strategy is presented by simultaneously adjusting the amplitude and frequency of spindle speed variation. The effect of SSV parameters on stability improvement in turning processes including the tool wear is first investigated to demonstrate the necessity of simultaneously adjusting the amplitude and frequency for chatter suppression. Then, the proposed chatter suppression system is introduced, where two SSV parameters are simultaneously adjusted with optimal fractional-order proportional integral differential (FOPID) controllers to keep the chatter indicator close to a target value. Moreover, the FOPID controller is optimally tuned with the JADE algorithm. The effectiveness of the proposed method is verified by comparing simulated results of different SSV parameters adjusting strategies. Finally, machining tests are conducted to validate that the proposed chatter suppression method outperforms the existing SSV method in flexibility and effectiveness.

Analysis of Vibration During Turning Process of Different Materials

In this article, we would like to introduce the problems caused by vibrations in case of polymer turning processes. Nowadays there is a lot of research in this topic, to avoid the unnecessary phenomena of vibrations. The two most common methods are the Spindle Speed Variation (SSV), and the Vibration Assisted Machining (VAM). In case of SSV, the CNC machine can increase and decrease the speed of spindle continuously during turning which can significantly reduce the effects of chatter. This method is beneficial for longer workpieces when there is not any support except the chuck. Vibration-assisted machining can be used to minimise the problems caused by vibrations. VAM combines precision machining with small-amplitude tool vibration to improve the fabrication process. It has been applied to some processes ranging from turning, drilling to grinding. Based on the enumerated above we made some trial measurements about the basic vibrations of the turning tool shank. The tests were done on an NCT EUROturn-12B CNC machine which can found in the workshop of our institute. The tested material was Polyamide 6 because this is the most commonly used polymer in the industry. In the future, we would like to test some other basic and composite polymer materials too. The equipment was served by a specialist from SPM Budapest Kft. With these tests, our goal was to make sure that the equipment and the measuring setup are suitable for our future research.