以電流及振動訊號監測微銑削刀具磨耗之研究

Study of Current and Vibration Signals for Monitoring Tool Wear in Micro Milling

黃門(Men Huang)

指導教授 ： 李貫銘

國立臺灣大學/工學院/機械工程學研究所/碩士(2016年)

https://doi.org/10.6342/NTU201603648

摘要

在微銑削作業中，刀具磨耗之即時監測方法仍有諸多困難，雖然已有許多研究利用不同的切削訊號進行磨耗預測，但在設備的成本及安裝上難免有些限制，而在訊號分析及磨耗辨識的方法上，有些需要較長的運算時間，或是在預測模型的建立上需要較多的實驗數據，因此較不符合工業上的實際應用。
為了達到即時監測的目的，本研究利用主軸電流以及加速規感測器，進行刀具狀態的監測，因為主軸電流為機台本身的訊號來源，並不需要額外的感測器，其時域的訊號在刀具磨耗的過程隨著刀具承受的切削力有足夠的變化，並反應在電流值的大小上，而加速規的振動訊號的時域訊號在本研究中並沒有明顯的變化趨勢，因此主要觀察在刀具磨耗過程中其頻域訊號的變化，像是不同刀刃通過頻率的倍頻或是頻域能量的改變，幫助觀察刀具和工件接觸時的振動情形。
在本研究的加工條件範圍中(不同的切削速度及進給速度)，我們利用特徵向量的方法分析振動的頻域訊號，將刀具磨耗的嚴重程度分成三個或兩個階段，但準確度過低，且預測換刀的時機也過早，沒有辦法在適當的時機點換刀。主軸電流的部分，我們可以觀察到電流隨著刀具磨耗的變化，並將主軸電流值進行迴歸分析處理，進行刀具磨耗的預測，根據工件表面粗糙度的變化設立閥值，當主軸電流預測的磨耗達到達到設定的閥值時更換刀具，以此達到穩定表面精度的效果。

關鍵字

微銑削 ； 刀具磨耗 ； 電流 ； 加速規

並列摘要

In micro milling, there are still many difficulties to monitor the tool wear on-line. Although many researchers have used different cutting signal to monitor tool wear, cost and setting of equipment are still the restriction. Some signal analysis methods take long time to compute or need a lot of experimental data, so it is hard to use these ways in real industry.
This study use spindle current and accelerometer vibration signal to monitor the tool wear. Spindle current don’t need extra sensor to get the data, and current signal has a good response to cutting force in cutting process. Accelerometer time-domain vibration signal in this study doesn’t have a clear changing tendency. We observe frequency-domain vibration signal like tool pass frequency and the magnitude change to realize the contact condition between tool and workpiece.
This study presents an experiment investigation of micro milling at different cutting speed(39.6m/min,59.3m/min and 79.1m/min) and feeds(1μm/rev,1.5μm/rev and 2μm/rev) under dry cutting. According to the results, after the analysis with feature vectors, tool wear can be divided into two or three wear level, but the accuracy is so bad that users cannot change tool at a suitable time. On the other hand, the current signal will increase as tool wear increase. Current signal can be used to calculate the tool wear by regression analysis. If tool wear reach the threshold which set according to the surface accuracy, users can change the tool before the surface accuracy decline.

並列關鍵字

micro milling ； wear ； current ； accelerometer

參考文獻

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