109年
姓名

黃子耀 Tzu-Yao Huang

題目

虎鉗夾持力對於銑削加工訊號影響之研究

Effect of Vise Clamping Force on Machining Signals  in Milling

大綱

摘要

    隨著工具機技術愈趨成熟,製造業朝向智慧化發展,對於刀具磨耗的監控、機械系統的故障預測之模型開發也越來越受重視。雖然已有許多研究利用不同的切削訊號來進行刀具磨耗的預測,然而加工訊號容易受到加工參數、刀具幾何、機台雜訊等影響而改變,且大多數研究中,是根據特定的切削參數所建立之刀具磨耗監控模型並進行預測,泛化性難以驗證。

    為了探討虎鉗夾持力大小對加工訊號的影響,實驗設計上,本研究在虎鉗上安裝荷重元監控夾持力,並設定600 kgf 1400 kgf 兩種參數。觀察這兩種夾持力下的三軸加速規與聲射訊號其時域以及頻域上的差異,並利用這些訊號特徵建立類神經網路模型進行刀具磨耗的監測。本研究嘗試以單一夾持力的加工訊號為訓練資料集建立模型,再以不同夾持力的加工訊號為測試資料集,來檢驗模型在面對不同夾持力的加工訊號時的辨識能力。

    透過正規化與非線性模型實降低刀具與加速規之相對距離造成的能量誤差以及消除不同進給大小造成的能量差異,提升了模型的穩定性。分析結果顯示,虎鉗夾持力改變使得Z方向(主軸方向)之振動時域訊號及頻域能量分佈發生明顯改變,X方向(進給方向)Y方向(夾持方向)振動與聲射之時域訊號與頻域能量分佈改變較小。由於訊號特徵受到夾持力影響而發生改變,導致類神經網路模型在對不同夾持力下的加工數據進行刀具磨耗辨識準確率降低。而經由特徵工程的改善,X方向振動訊號與聲射訊號所建立之模型,在面對不同加工參數的數據時,辨識準確率依序從74.7%52.5%提升至90.4%83.2%

關鍵字虎鉗夾持力、刀具磨耗、振動訊號、聲射訊號、類神經網路

Abstract

    In recent years, the development of models for tool condition monitoring and predicting mechanical system failures attract more and more attentions. Although different cutting signals have been studied for accurately predicting tool wear, it is found that the cutting signals are easily affected by processing parameters, tool geometry, etc.. Therefore, in most studies, experiments were only based on specific processing parameters.

    In order to understand the influence of the clamping force of the vise on cutting signal, a load cell was installed on the vise and set the clamping forces to be 600 kgf and 1400 kgf. The difference in the time domain and frequency domain signals of the three-axis accelerometer and the acoustic emission under these two clamping forces were observed. These signal characteristics were used to build up a neural network model for tool condition monitoring. This study first built up a model with cutting signals based on 600 kgf clamping force, and then used the cutting signals under different clamping forces as the test data set to test the accuracy of the model.

    The results showed that the signal characteristics are affected by the clamping force, resulting in prediction error of the neural network model. Through the improvement of feature engineering, the accuracy of the model based on X-direction vibration signal and acoustic emission signal have been increased to 90.4% and 83.2%, respectively.

Keywords:  Vise clamping force; Tool wear; Vibration signal; Acoustic emission; Neural network