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1. REVIEW OF KEI METHOD-BASED DIMENSIONAL MEASUREMENT, POSITIONING CONTROL AND PART INSPECTION

   Wang, Zhikun ; Lee, ChaBum ( July 2022 , Manufacturing Engineering and Science Conference)

   This paper reviews knife-edge interferometry (KEI) capable of inspection and metrology for various engineering applications, including displacement measuring sensors for dynamic system controls and edge quality of the parts, such as cutting tools, corrosive blades, and photomask patterns. This paper includes the modeling, design, and data analysis of KEI. With the expanding market of manufacturing industries, edge topography and instrumentation technology become more and more vital to industrial manufacturing-related applications such as cutting tool wear inspection, photomask edge roughness determination, and edge corrosion propagation monitoring. Due to the limitation of measurement requirements like non-contact (photomask inspection), in-situ (cutting tool inspection), and real-time (corrosion propagation monitoring), there are only a few methods available in the market above, and those methods are based on post-processing. The KEI is capable of on-machine measurements, especially for the nanopositioning systems, providing a large working range and positioning accuracy compared with the conventional displacement sensor. This review addresses the current and future KEI technology. Here, including the theoretical approaches to KEI, this review details the data analy 

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2. A Fringe Pattern Analysis Technique for Photomask Line-Edge-Roughness Characterization

   Zhikun Wang, Kuan Lu ( June 2023 , American Society of Mechanical Engineers: Manufacturing Science and Engineering Conference)

   Line-edge roughness (LER) characterization is vital in the semiconductor industry to this day. This paper presents an EKEI (enhanced knife edge interferometry)-based system for photomask LER characterization. From the given EKEI-based system, the LER on the photomask pattern can be characterized. In this paper, the Fresnel (F) number-based geometrical optical model was developed for the LER-induced edge diffraction fringe simulation. The LER here was defined by three times the standard deviation of the edge profile on the photomask. Periodic rectangular functions were employed to characterize LER effects on the diffraction fringe patterns in simulation. The simulation-generated fringe pattern was then analyzed by cross-correlation. From the simulation result, the fringe pattern will get attenuated when adding the LER onto the line edge profile. Once the LER value increases, some of the high-order fringes vanish. A negative correlation between the similarity and the LER value was discovered. From the F number-based simulation model, the real photomask decorated with different LER values was designed and fabricated. After the photomask writing process, we used the EKEI system to scan the LER-programmed pattern for photomask LER characterization. By using the cross-correlation, the same trend was found in the experiment and simulation results. The fringe pattern from the edge was attenuated while the LER was added to the edge. The geometrical-based simulation and analysis model for photomask LER characterization was validated. From the simulation results, the fringe pattern from the edge was attenuated when adding LER on the edge. The experiment results show good agreement with the simulation ones. In sum, the proposed EKEI-based system has great potential to be utilized for on-machine photomask LER characterization and those defect inspection. The F number-based geometrical optical model also has the potential for diffraction-free pattern design and analysis. 

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3. Knife-edge interferogram analysis for corrosive wear propagation at sharp edges

   https://doi.org/10.1364/AO.417572  

   Wang, Zhikun ; Lee, ChaBum ( February 2021 , Applied Optics)

   This paper presents a novel noncontact measurement and inspection method based on knife-edge diffraction theory for corrosive wear propagation monitoring at a sharp edge. The degree of corrosion on the sharp edge was quantitatively traced in process by knife-edge interferometry (KEI). The measurement system consists of a laser diode, an avalanche photodiode, and a linear stage for scanning. KEI utilizes the interferometric fringes projected on the measurement plane when the light is incident on a sharp edge. The corrosion propagation on sharp edges was characterized by analyzing the difference in the two interferometric fringes obtained from the control and measurement groups. By using the cross-correlation algorithm, the corrosion conditions on sharp edges were quantitatively quantified into two factors: lag and similarity for edge loss and edge roughness, respectively. The KEI sensor noise level was estimated at 0.03% in full scale. The computational approach to knife-edge diffraction was validated by experimental validation, and the computational error was evaluated at less than 1%. Two sets of razor blades for measurement and control groups were used. As a result, the lag will be increased at an edge loss ratio of 1.007/µm due to the corrosive wear, while the similarity will be decreased at a ratio of$5.4\times <\#comment/>{10}^{-<\#comment/>4}/\text{µ<\#comment/>}\mathrm{m}$with respect to edge roughness change. Experimental results showed a good agreement with computational results.

    

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4. Tool wear area estimation through in-process edge force coefficient in trochoidal milling of Inconel 718

   Shah A. ; Agarwal A. ; Mears L. ( January 2023 , Manufacturing letters)

   The rapid wear and premature failure of the cutting tool are prone to happen due to increased forces during machining difficult-to-cut materials such as Inconel 718. The application of alternative toolpath such as trochoidal milling has significantly improved tool life and reduced the overall cycle time of the process. The wear pattern of the tool has a direct impact on the cutting forces, which increases with tool deterioration. The cutting forces in milling are modeled through the mechanistic force model and can be designated through a set of force coefficients, i.e. cutting and edge representing the shearing and ploughing phenomenon of metal removal. It has been established in the literature that tool wear has a considerable effect on the value of edge force coefficients. This paper aims to determine the in-process edge force coefficients for the trochoidal toolpath and correlates them with the corresponding flank wear area. The proposed correlation will further assist in predicting the level of flank wear area based on the force values in trochoidal milling. 

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5. A novel approach for in-situ characterization and probabilistic prediction of cutting tool fatigue in machining of Ti-6Al-4V

   https://doi.org/10.1016/j.mfglet.2023.10.002  

   Hartley, Avery ; Money, Jenna ; Schoop, Julius ( November 2023 , Manufacturing Letters)

   The wear behavior of cutting tools is highly complex due to combined thermal, mechanical, and chemical loads. As a result, most current tool-wear prediction methodologies are either empirical or highly oversimplified analytical or numerical models of stable abrasive and diffusive wear mechanisms. To predict the complex physics of catastrophic tool edge chipping, which in practice bounds feasible process parameters, this manuscript presents a novel approach for in-situ characterization of tool edge fatigue loads and probabilistic prediction of the likelihood of time to fracture. The results of the analysis suggest encouraging possibilities for more physics-informed and data-driven process design. 

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