近年來工具機技術愈發成熟,在加工應用上也越來越廣泛。然而,由於一直以來沒有精確可靠的切削數學模型能夠預測刀具磨耗、表面質量等,尤其是近幾年高精度加工應用具有很大的需求,因此開發加工過程中的監控系統便顯得格外重要。過去大多數研究中常用動力計來測量切削力,但其價格昂貴且占工作空間,使加工受到諸多限制。為了解決這個問題,已有許多文獻提出了幾種基於壓電、壓阻材料和電容換能器的切削力感測器。然而,高速加工時切削力極小且上述大部分文獻提出的感測器都只是模型,很少提及感測器元件和電路前端之間的集成,這是決定感測信號完整性和信噪比的關鍵。因此,本研究旨在提出一種可行的解決方案,在不破壞刀具的結構下嵌入信號線並使用性能佳的壓電感測元件。使用聚偏二氟乙烯 (PVDF) 感測元件與其連接的調節電路集成在一起,以實現量測車刀即時切削力之目的。感測器的動態特性透過脈衝試驗進行評估,且同時也在不同的切削條件下進行了切削試驗。研究結果表顯示,所設計的感測器在不同切削條件下會量測到不同的切削力,因此是一可行且有效的方法,並可推展應用至其他切削加工。
In high precision machining application, an intelligent machining system is promising since it is necessary to monitor the cutting force during the cutting process. Dynomometer is commonly used in most researches to measure cutting force, but it is expensive and limit the working space. To address this, several cutting force sensors based on piezoelectric, piezoresistive materials, and capacitive transducers have been demonstrated. However, the cutting force is extremely small during high speed machining. In addition, most of the aforementioned works are merely prototypes and very few of them touch upon the integration between the sensor component and the circuit front-end, which are actually critical in determining the sensing signal integrity and noise performance. Therefore, this thesis provides a possible solution by embedding the signal line in the tool and selecting material with high piezoelectric coefficient. In this work, a fabrication process flow that allows the integration of a polyvinylidene fluoride (PVDF) sensing element with its following conditioning circuit for real-time cutting force in turning tools was presented. In particular, this process directly integrates metal wires into the tool shank by modifying the screw of the clamp and design a printed circuit board (PCB) for signal transmission. The dynamic characteristics of the prototype were estimated by impulse test, and the cutting tests were also carried out. It turns out that the performance of the designed sensor is feasible under variant cutting condition. On the other hand, dynamic disturbances were identified, some approaches for design optimization were proposed.
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