Patent ID: 7455568

Claim:
A water jet-processing machine comprising a workpiece to be cut holding table having a holding surface for holding a workpiece to be cut, a nozzle for emitting a jet of processing water to the workpiece to be cut held on the holding surface of the workpiece to be cut holding table, a processing water supply means for supplying processing water containing abrasive grains to the nozzle and a moving means for moving the nozzle in a direction perpendicular to the holding surface of the workpiece to be cut holding table, wherein the machine further comprises a processing sound wave detection means for detecting a processing sound wave generated by processing water ejected from the nozzle to the workpiece to be cut and a control means for controlling the moving means based on a detection voltage signal detected by the processing sound wave detection means, and wherein the control means comprises a storage means for preforming a data map converting data on a frequency of a processing sound wave stored as a voltage signal corresponding to the interval between the nozzle and a surface of the workpiece to be cut into a voltage signal and beforehand storing the data map, and obtains the interval between the nozzle and the surface of the workpiece to be cut based on the frequency data stored in the storage means and a detection voltage signal detected by the processing sound wave detection means to control the moving means so that the interval becomes a predetermined value.