工具機加工精度衰減之預測模式研究

Forecasting Models for Machining Accuracy Degradation of Machine Tools

陳希銘(Hsi-Ming Chen)

指導教授 ： 范光照

國立臺灣大學/工學院/機械工程學研究所/博士(2011年)

https://doi.org/10.6342/NTU.2011.10514

摘要

工件的尺寸精度取決於工具機的加工精度。工具機在長時間的切削加工操作下，導軌表面因磨耗作用而呈現凹陷，因此造成工作台在運動時產生角度誤差，角度誤差會因阿貝原理而放大加工誤差。
本研究建立工具機滑軌磨耗數學模型，在已知切削力與工具機參數，可計算滑軌接觸變形時影響工作台運動的幾何誤差，以及預測長時間操作後之滑軌磨耗情形與加工誤差量。依據研磨磨耗理論計算滑軌磨耗量，由於磨耗係數為滑動距離之函數，因此本研究經由測試平台之實驗結果修正磨耗係數，提高磨耗預測之準確度。
另外本文建構工具機加工精度預診系統，藉由自製低成本高精度之自動視準儀即時量測工作台運動時之角度誤差，此角度誤差即為工具機加機工精度失效的特徵值，由邏輯斯迴歸分析此特徵值而作為評估工具機加工精度之健康狀況，另外經由灰色預測理論預測短期之加工精度健康狀況變動量，此外工具機操作者或廠商可經由遠端即時監控工具機之加工精度，以便於維護與保養。

關鍵字

工具機 ； 精度衰減 ； 滑動磨耗 ； 接觸變形 ； 自動視準儀 ； 預測

並列摘要

Machine tool has to maintain its accuracy for quality control of products. After a long period of cutting operations, obvious wear will be happened on the contact surface of the slide and the guideway. Such a wear will degrade the accuracy of machine tool due to the increase of Abbé errors.
This thesis composes of two research topics. The first topic is Prediction of machining accuracy degradation of machine tools. The other topic is the prognostic system for machining accuracy assessment.
For the first topic, this research proposes a mathematical model so that, at given cutting forces and parameters of the slide-guideway, it is able to calculate the geometric errors of the slide due to contact deformation caused by the wear of the guideway and then predict the positioning errors after a long-term operation. Cutting forces applied to the worktable will cause reaction forces on contact surfaces between the slide and the guideway. Such reaction forces can be solved by static equilibrium equations of deformed free-body diagram of the slide. The induced abrasive wear can then be estimated. Case study on a heavy duty machine tool with slide-guideway will show the magnitude of wear on the sliding surface and the consequently caused geometric errors of the moving axis.
For the second topic, this research proposes the prognostic system for machining accuracy assessment. The autocollimator modified from the DVD pickup head is used as the angle sensor for measuring the angular errors of machine tools. The angular errors as the features used to detect the degradation of machining accuracy. The logistic regression is used to assess the machining accuracy of machine tools, and the theory of Grey forecasting model is applied to predict the degradation trend of machining accuracy. Furthermore, the machine tools user can monitor the angular errors of machine tools by remote monitoring system, which would lead to proactive maintenance processes to minimize downtime of machine tools, thus increasing efficiency of operations and manufacturing.

並列關鍵字

machine tool ； accuracy degradation ； slide-guideway ； contact deformation ； wear ； autocollimator ； prediction

參考文獻

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