電化學磨削健康診斷系統

Abstract

電化學磨削(Electrochemical grinding , ECG)是結合電化學與磨削作用的特性，但在實際加工中往往需要人工經驗判斷加工過程中的種種現象，為了實現自動監控加工過程，本研究將加速規和聲發射感測器安裝在機台上，加速規訊號經濾波後使用短時傅立葉時頻譜進行分析，聲發射感測器則使用快速傅立葉轉換呈現結果。 研究中發現聲發射感測器可以偵測材料硬度變化時的頻域變化，而加速規則是可以利用時頻譜判斷在實驗過程中所發生的預警現象(火花特徵)，並且在加工過程中也發現機台存在著螺桿背隙以及平台傾斜之問題，導致後續磨削中的電化學反應不穩定。 研究利用田口L27直交表進行實驗，探討加工參數為脈衝電壓、脈衝時間、轉速、平移速率以及深度，實驗結果顯示，不同磨削深度和平移速率對頻率響應有明顯影響，深度增加會導致更強的頻率，而較高的平移速率會增加火花特徵的發生機率。 在電化學反應方面，加工過程中的深度過深和平移速率過快會導致實驗過程中轉變為電化學放電反應，而此電化學放電反應的結果會使試片的硬度和表面粗糙度均比穩定電化學反應的結果更差。本研究也探討了不同平移速率下脈衝電壓對材料組織的影響，結果顯示，隨著脈衝電壓的增加，促進鋁元素的移除，並且材料的孔隙率主要受到脈衝電壓的影響。平移速率的增加對材料孔隙率的影響較小，表明平移速率對於材料結構的影響相對有限。

Electrochemical grinding (ECG) is a process that combines the characteristics of both electrochemical action and grinding. However, in practical machining, various phenomena often need to be judged based on human experience. To achieve automatic monitoring of the machining process, this study installed accelerometers and acoustic emission sensors on the machine. The accelerometer signals were analyzed using Short-Time Fourier Transform (STFT) after filtering, while the acoustic emission sensor results were presented using Fast Fourier Transform (FFT). The study found that the acoustic emission sensor can detect changes in the frequency domain when there are variations in material hardness, while the accelerometer can utilize the time-frequency spectrum to identify warning phenomena (such as spark characteristics) that occur during the experiment. Furthermore, during the machining process, it was also discovered that there were issues with the machine, such as screw backlash and platform tilt, leading to instability in the electrochemical reactions during subsequent grinding. The study conducted experiments using a Taguchi L27 orthogonal array to investigate machining parameters such as pulse voltage, pulse duration, spindle speed, feed rate, and depth. The experimental results showed that different grinding depths and feed rates have a significant impact on the frequency response, with increased depth leading to stronger frequency signals and higher feed rates increasing the likelihood of spark characteristics. In terms of electrochemical reactions, excessive depth and too fast feed rate during the machining process can result in the transition to electrochemical discharge reactions, leading to poorer hardness and surface roughness of the test piece compared to stable electrochemical reactions. This study also explored the impact of pulse voltage on the material structure at different feed rates. The results showed that as the pulse voltage increased, the removal of aluminum elements was promoted, and the material's porosity was primarily influenced by the pulse voltage. The increase in feed rate had a relatively minor effect on material porosity, indicating that feed rate has a limited impact on material structure.