Investigation of Milling Stability under Cutting Fluid Supply by Microphone Signal Analysis
Rong-Mao Lee, Pao-Ting Liu, and Cheng-Chi Wang
(Received January 18, 2018; Accepted July 17, 2018)
Keywords: milling vibration, milling noise, scatter diagram of time domain, stability lobe diagram
Force and acceleration are the most well-known signals for the monitoring of milling vibration. However, the noncontact and low-cost microphone is also a potential choice for cutting vibration measurement. The superior detection sensitivity of the microphone against milling dynamics was preliminarily verified. However, the limitations of microphones to record milling vibration were also reported in the past two decades, such as the vibration identification accuracy under the influence of environmental noise. In this work, the microphone signal beyond 5 kHz is employed in the milling stability analysis to diminish the effect of low-frequency environmental noise. In addition, almost all of the current studies for cutting noise analyses are conducted without cutting fluid (dry cutting). This is far from most of the practical manufacturing processing. The cutting fluid is used in this work and a waterproof device is particularly designed to ensure the microphone operation against the cutting fluid. The microphone signal is analyzed on the basis of the scatter diagram of time domain (SDTD) to discuss the variation trend due to the milling stability. In addition, both the fast Fourier transform (FFT) and short-time Fourier transform (STFT) were employed to clarify the signal characteristics in the frequency domain. Finally, the finished workpiece surface was checked with the stability lobe diagram (SLD) to verify the acoustic analysis results.
Corresponding author: Rong-Mao Lee