Preliminary study for online monitoring during the punching process

Monitoring of the punching operation plays an important role in enhancing product quality and tooling protection. In sheet metal working, most monitoring methods use tonnage/cutting force signal. In this study, the potential of vibration signal in the frequency range from 0 to 1000 Hz for punching monitoring is reported. The experiment is conducted by using a punch with a diameter of 0.8 mm and a speed of 50 rpm. The sheet material is SUS304 with a thickness of 0.5 mm. During the experiments, the signals, the tool conditions, and the burr formation are observed. The results show that there is a correlation between tool conditions with vibration signal. The influence of tool wear, an indication of punch breakage, and an incident of punch breakage are prominent. By the development of wear, the burr height increases and an increase in vibration amplitude is observed. When the burr height grows up to 3.5 times, certain vibrational peak amplitude increases around 15 times. This will be remarkable results for online monitoring because the off-line measurement of burr height can be substituted by vibration measurement. Based on these results, it can be concluded that the vibration signals at this frequency range have the potential for monitoring the tool condition and burr formation in the punching process.