The application of response surface methodology to optimum parameters of rigid tapping processing

The rigid tapping function of the CNC machine tool can manufacture thread rapidly and aims at a short tapping time and a small synchronization error. A small synchronization error represents high accuracy and long tool life, but a short tapping time influences the accuracy. Therefore, the objective of this study was to use fixed synchronization errors to obtain the shortest machining time. In the parameter adjustment process of this study, the frequency response was adjusted for the Z-axis at first, and the resonance frequency was eliminated from three filtering parameters, namely, frequency, bandwidth, and damping. Moreover, the value of position gain was increased by enhancing the speed gain, and the frequency response was adjusted to the optimum condition. The response surface methodology was used to analyze the influence of variable factors on rigid tapping, and the significant and nonsignificant factors. The significant factors include the position gain and acceleration/deceleration time constant. After the prediction model equation was created, the optimum parameter setting could be found. When the machine tool was taken back for cutting verification, the synchronization error was reduced by 621 pulse (92%), the tapping time was shortened by 2 s (7.7%), and the accuracy of dimensional difference was increased by 0.216 mm (26%). This study's parameter adjustment method can yield a highly efficient thread processing.