Study on inprocess sensing of tool failure utilizing microphones

点击翻译按钮获取中文摘要

The study deals with the monitoring system for turning process, and investigates under various cutting conditions. Cutting sound is detected by microphones, and is transformed to frequency spectrum by a FFT analyzer. This pays attention to the changes of peak on frequency spectrum of cutting sound as tool wear increases. Experimental results show that when flank wear increases, the peak value increases and the peak frequency reduces slightly.The method utilizing cutting sound is very effective to detect tool wear as it is non-contact measurement, but at the same time it has a problem. There are many sound sources in practical environment. Surrounding sound interrupts the monitoring system and makes accuracy of detection of tool wear worse. Therefore, it is necessary and indispensable for a practical monitoring system utilizing cutting sound to have an ability to specify the sound source locations.The study also makes an attempt to give the acoustic sensor sharp directivity in order to detect the only sound from specified sound source. As the method to make directivity, two methods which use a microphone-array or a parabolic refledctor are adopted. Each method is experimentally investigated whether it can specify location of several sound sources and distinguish from other sound sources. In the experiment with the microphone-array, two cutting processes are examined with two lathes.At that time, sounds generated from the lathes are identified by varying direction of the microphone-array. The experiment shows that the array system can hold down sensitivity for unexpected sound from other source than a pointed sound source by the array, and can distinguish expected sound from several sound sources. Another method by the parabolic reflector is examined as well, and almost the same results are obtained.