Among all the monitoring data which could be captured in a machining process, the cutting forces could convey key knowledge on the conditions of the process. When the machining involves a single cutting edge the relationship between the output forces (measured with off-the-shelf dynamometers) and condition of the process, is somehow straight forward. However, when multiple cutting edges are in contact with the workpiece, the conventional dynamometers, that cannot separate the reaction forces on each cutting edge, loose significant information that could be used to in-detail monitor the machining process. To this end, this paper presents a novel concept of instrumented wireless milling cutter system with embedded thin film sensors in each cutting inserts, thus the cutting forces acting on each cutting edge could be monitored without reducing the stiffness and dynamic characteristics of the machining system. For this to happen, a dedicated milling force decoupling model for the developed instrumented milling cutter system is proposed and calibrated, and for the first time the accurate online estimation of the separate inserts' working conditions is achieved. The validation demonstrates a satisfactory agreement between the forces measured from the dynamometer and the proposed monitoring system prototype with the error less than 10%. Furthermore, the experimental results also indicate that the monitoring system prototype could also identify the tool insert conditions such as worn and chipped, which could be of high relevance to the analysis of the insert failure mechanism and its progress. Not only the proposed method and easy implementable but above all, it allows the monitoring of the condition (e.g. worn, chipped) of each insert, ability that has not been previously reported.

Thin-walled workpieces, such as aero-engine blisks and casings, are usually made of hard-to-cut materials. The wall thickness is very small and it is easy to deflect during milling process under dynamic cutting forces, leading to inaccurate workpiece dimensions and poor surface integrity. To understand the workpiece deflection behavior in a machining process, a new real-time nonintrusive method for deflection monitoring is presented, and a detailed analysis of workpiece deflection for different machining stages of the whole machining process is discussed. The thin-film polyvinylidene fluoride (PVDF) sensor is attached to the non-machining surface of the workpiece to copy the deflection excited by the dynamic cutting force. The relationship between the input deflection and the output voltage of the monitoring system is calibrated by testing. Monitored workpiece deflection results show that the workpiece experiences obvious vibration during the cutter entering the workpiece stage, and vibration during the machining process can be easily tracked by monitoring the deflection of the workpiece. During the cutter exiting the workpiece stage, the workpiece experiences forced vibration firstly, and free vibration exists until the amplitude reduces to zero after the cutter exits the workpiece. Machining results confirmed the suitability of the deflection monitoring system for machining thin-walled workpieces with the application of PVDF sensors.

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A novel Lorentz-FDTD method was proposed to analyze scattered fields from moving complex dielectric in this paper. Different from other methods, we present a special way to introduce the incident plane wave in the moving system. The scattered fields are transformed from the moving system to the rest system with the Lorentz transformation and linear interpolation technique. Numerical results verify the accuracy and validation of the proposed method to calculate scattered fields from moving dielectric slabs.

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