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This paper presents a novel non-destructive testing system, magneto-eddy current sensor (MECS), to enable surface profiling of dissimilar materials by combining magnetic sensing for ferromagnetic materials and eddy current sensing for non-ferromagnetic materials. The interactions between an electromagnetic field and non-ferromagnetic surface and between a magnetic field and ferromagnetic surface were measured by MECS. The MECS consists of a conic neodymium magnet and a copper coil wound around the magnet. Aluminum and steel surfaces bonded together were prepared to test non-destructive surface profiling of dissimilar materials by MECS. The interactions between an electromagnetic field and aluminum surface were characterized by monitoring the impedance of the coil, and the interactions between a magnetic field and steel surface were characterized by using a force sensor attached to the neodymium magnet. The magnetic and electromagnetic effects were numerically analyzed by finite element model. The developed MECS showed the following performance: measurement spot size 5 mm and 10mm, dynamic measurement bandwidth 15 kHz and 10 kHz, measuring range 25 mm and 17 mm, polynomial fitting error 0.51% and 0.50%, and resolution 0.655 μm and 0.782 μm for nonferromagnetic and ferromagnetic surface profiling, respectively. This technique was also applied to surface profiling and inspection of the rivet joining sheet materials. The results showed the MECS is capable of non-destructively monitoring and determining the riveting quality in a fast, large-area, low-cost, convenient manner.

This paper introduces a simple three-dimensional (3D) stereoscopic method using a single unit of an imaging device consisting of a charge-coupled device (CCD) and a zoom lens. Unlike conventional stereoscopy, which requires a pair of imaging devices, 3D surface imaging is achieved by 3D image reconstruction of two images obtained from two different camera positions by scanning. The experiments were performed by obtaining two images of the measurement target in two different ways: (1) by moving the object while the imaging device is stationary, and (2) by moving the imaging device while the object is stationary. Conventional stereoscopy is limited by disparity errors in 3D image reconstruction because a pair of imaging devices is not ideally identical and alignment errors are always present in the imaging system setup. The proposed method significantly reduced the disparity error in 3D image reconstruction, and the calibration process of the imaging system became simple and convenient. The proposed imaging system showed a disparity error of 0.26 in the camera pixel.

This paper introduces a computer vision technique for wafer particle metrology and inspection. Artificially generated particle images based on their color properties were used to verify HSV (hue, saturation, value) color space models of each particle and to demonstrate how the proposed method efficiently classifiesparticles by their types with minimum crosstalk. A high-resolution microscope consisting of an imaging system, illumination system, and spectrometer was developed for the experimental validation. The three kinds of micrometer-scale particles were randomly placed on the wafers and the images collected under the exposed white light illumination were analyzed and segmented by particle types based on pre-developed HSV color space models specified for each particle type. The proposed method is expected to inspect and classify various wafer particles in the defect binning process.

Monitoring cutting tool quality in the machining process is essential to the success of part manufacturing. To directly monitor the information of cutting tools under the drilling or milling operations, this paper presents a novel 3D imaging technique to enable direct cutting tool geometry measurement. This method combines stroboscopy and stereoscopy, this strobo-stereoscopy, which synchronizes the stroboscopic illumination system with the spindle control system and enables in-situ reconstructing 3D images of cutting tools. For the phase-locked mode, this technique can lock the image of the cutting tool while in motion. On the other hand, for the phase-shifting mode, all facets around the cutting tool will be scanned by shifting the phase of the light signals while collecting dimensional target information. Experimental studies of phase-locked and phase-shifting modes for monitoring an end mill tool and a wood rolling pin were presented. The directly measured maps and whole 3D images on the target tools verify the capability of the geometry identification of the proposed strobo-stereoscopic imaging technology. Lastly, the potential applications of the proposed technology were discussed.

Spindle dynamic conditions such as stiffness, damping, runout, and resonance frequencies are the most important factors to determine the quality of the machined part. Thus, spindle dynamic characterization to in-situ identify the spindle behavior is crucial to achieve high dimensional accuracy during the machining. This paper presents a new class of dimensional sensors, the so-called curved-edge sensors (CES), capable of spindle dynamic characterization and in-situ spindle condition monitoring while machining. Unlike conventional dimensional sensors such as capacitive proves or eddy current probes whose sensitivities are sensitive to the curvature of the target surface and lateral motion of the spindle, CES is not sensitive to those effects that CES can be used for spindle metrology, providing more accurate dimensional information available for spindle dynamic characterization. In this study, two-axis CES were embedded inside the aerostatic spindle system not to disturb the spindle system while machining a part, even under working fluid conditions. The CES showed the sensitivity 0.301 and 0.304 V/μm along the X and Y axes, and the linearity was 0.06 % and 0.05 % in full scale, respectively. In addition to the calibration, bandwidth, noise level, and reliability of CES were characterized. Also, the spindle runouts at different speed conditions were characterized by CES, and the cutting forces were in-situ estimated by multiplying 3 × 3 spindle stiffness matrix and the measured displacement.

This paper introduces an imaging technique to enhance three-dimensional (3D) surface profiling of the machined part by using a feature-selective segmentation (FSS) and merging technique. Spatially-resolved 3D stereoscopic images were achieved compared with those of the conventional filtering-based imaging process. Two identical vision cameras simultaneously take images of the parts at different angles, and 3D images can be reconstructed by stereoscopy algorithm. High-pass and low-pass filtering of the images involves data loss and lowers the spatial resolution of the image. In this study, the 3D reconstructed image resolution was significantly improved by automatically classifying and selectively segmenting the features on the 2D images, locally and adaptively applying super-resolution algorithm to the segmented images based on the classified features, and then merging those filtered segments. Here, the features are transformed into masks that selectively separate the features and background images for segmentation. The measurement system scanned the machined part with various shape and height information. The experimental results were compared with those of a conventional high-pass and low-pass filtering method in terms of spatial frequency and profile accuracy. As a result, the selective feature segmentation technique was capable of spatially-resolved 3D stereoscopic imaging while preserving imaging features. The proposed imaging method will be implemented with strobo-stereoscopy for in-process 3D surface imaging.

This paper introduces a spindle-integrated 3-axis force sensor consisted of 2-axis curved-edge sensor (CES) for the radial direction and single axis capacitive sensor (CS) for the axial direction. The proposed single unit force sensor was used to monitor the carbon fiber-reinforced plastic (CFRP) milling and drilling processes and to understand their machining mechanics. Unlike a conventional cutting force sensor can non-contact measure the displacement of the spindle and estimate the cutting force by multiplying the spindle stiffness and the measured displacement. The force sensor unit was successfully integrated with the spindle and measured the cutting force while machining the CFRP plates with 0°, 45° and 90° fiber orientation. The conventional 3-axis force sensor was also used for a baseline comparison with the cutting force results measured by the proposed method. To monitor and characterize the delamination effect of CFRP, the time-frequency domain scalogram images analyzed form the cutting force data were used. Unique features were extracted according to the fact of existence and nonexistence of the delamination. Laser, the sensor measured capability, allowing for in-process CFRP machining process monitoring and CFRP defect mode prediction was discussed.

We have developed knife-edge interferometry (KEI) 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 reviewed 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 analysis method to feature the edge topographical information.

In this study, we investigated a novel approach that enables the in-process machining process monitoring at the tool-chip interface (TCI) by utilizing the impedance characteristics of the dielectric coating layer of the cutting tool. This study first analyzes the Nyquist diagram that characterizes the impedance response of a few micrometer-thick dielectric layers coated on the surface of the cutting tool by using an impedance analyzer under various temperature conditions for establishing the relationship between the relative permittivity of the dielectric layer and temperature. Consequently, the impedance of the dielectric layer was subject to change according to given temperature conditions. Thus, under its temperature-dependent impedance characteristics, the machining processes could be in-situ tracked and analyzed by directly probing the localized TCI, the so-called cutting hot spot, during the machining. The current source was implemented with the machining system and the variations of impedance at TCI were monitored during the facing process. As a result, impedance responses were remarkably changed under various machining conditions. The impedance was further characterized under the varying depth of contact and the impedance was decreased as the depth of contact increased. Therefore, the preliminary study demonstrated that an electrical impedance model of the dielectric coating layer may be applied for an in-process machining process monitoring method to analyze and assess the phenomenon of the machining process at the local TCI region. This study is expected to potentially provide utilization in advanced manufacturing to improve final part quality and productivity.

This paper represents a novel method to suppress the thermal effects of flexure mechanism-based nanopositioning system by fluid (air or water) flow under certain pressure conditions through the internal fluidic channels of the compliant structure. The nanopositioning system made of stainless steel was additively manufactured, and the rectangular fluidic channels were formed on each side of the double compound type flexure mechanism-based compliant structure. The motion behavior was characterized by measuring the stiffness and frequency responses of the compliant structure with the hammering test while filling compressed air or the water through the fluidic channels. The thermal behavior was characterized by measuring the temperature distribution over the compliant structure and thermal displacement under the various compressed air pressure and water flow-rate conditions. Dynamic behaviors of the nanopositioning system under various fluid-fed conditions were also characterized by the Finite Element Method and were validated with experimental results. As a result, the compressed air- or water-fed mechanisms have the following characteristics: (1) the damping may increase when the fluid exists in the channels, (2) the compressed air-fed mechanism can move the stage with nanometer precision with fast response time, and (3) the media filled in the fluidic channels significantly lower the temperature increase and reduce thermal displacement error. Interestingly, two-fluid flows of the compressed air and water showed a similar tendency in suppressing the temperature increase. The proposed method is expected to meet the increasing needs for nanometer motion accuracies and the efforts achieving high precision in the thermally stable environments requiring from semiconductor industries and precision machine tool industries.

A comprehensive review relevant to the design and fabrication of nanopositioning stages based on additive manufacturing (AM) technology has been for the first time introduced in the academic society. With the development of AM technology, AM has been applied in many engineering design areas such as aerospace, automotive, consumer electronics, and so on. Due to current limitations of AM tolerance (surface quality, form error), process obscurity (melting pool, layer adhesion), and cost (especially for metals or composites), there are only a small number of AM-applied devices that are currently available either in the market or in many industry sectors above. The flexure mechanisms that are typically employed in nanopositioning applications can provide a sub-nanometer resolution motion; however, their current manufacturing methods (milling, electric discharge machining, water jet machining) not only limit complicated flexure mechanisms in 3D geometries but also prevent designers from challenging novel topology optimizations. AM can overcome those limitations of fabrication and material distribution. Furthermore, it can allow new design approaches to topology optimizations. This review presents current and future AM-based precision motion device applications. Here, both design and fabrication of flexure mechanisms applied with current AM technology and the potential of further developments were discussed.

This paper presents novel surface profilometry for both geometric part error and metallurgical material property distribution measurements of the additively manufactured and post-processed rods. The measurement system, the so-called fiber optic-eddy current sensor, consists of a fiber optic displacement sensor and an eddy current sensor. The electromagnetic coil was wrapped around the probe of the fiber optic displacement sensor. The fiber optic displacement sensor was used to measure the surface profile, and the eddy current sensor was used to measure the change in permeability of the rod under varying electromagnetic excitation conditions. The permeability of the material changes upon exposure to mechanical forces, such as compression or extension and high temperatures. The geometric part error and material property profiles of the rods were successfully extracted by using a reversal method that is conventionally used for spindle error separation. The fiber optic displacement sensor and the eddy current sensor developed in this study have a resolution of 0.286 µm and 0.00359 μr, respectively. The proposed method was applied not only to characterize the rods but also to characterize composite rods.

This paper presents a novel dual-mode motion mechanism capable of achieving nanopositioning on a monolithic linear motion platform. Unlike conventional dual-mode stages that use piezoelectric (PZT)- and electromagnetic-combined or similar actuation mechanisms comprising two separate motion axes, the dual-mode actuation was developed by combining a PZT for a coarse motion and a fluidic pressure-fed mechanism (FPFM) for a fine motion and was implemented in a monolithic flexure stage fabricated by metal additive manufacturing. The FPFM actuates the flexure stage by pressuring the media in the fluidic channels created inside the flexure spring structures. Experimental tests were performed to investigate the performance of the dual-mode linear motion platform. The stiffness, damping, and frequency response functions of the dual-mode stage were experimentally characterized. The proportional–integral–differential control combined with dual-mode control was employed to control the position of the flexure stage while bidirectionally controlling the flow of compressed air for a fine motion. The FPFM motion showed a good response to 1 nm stepwise input (every 10 psi), and it was implemented to provide up to ∼10 nm fine motion along with the PZT coarse motion (1 µm). The hysteresis characteristics of the FPFM were also characterized and compensated to track the positioning error.

This paper represents a polymeric piezoelectric manufacturing process for sensing and actuation applications. The electric poling-assisted additive manufacturing (EPAM) process combining additive manufacturing (AM) with polymeric poling process has been recently introduced. This process keeps piezoelectric polymer dipoles well-aligned and uniform over a large area in a single-step direct printing process. Here, the EPAM process was employed to directly print polyvinylidene fluoride (PVDF) polymer; sensing and actuation performance was tested with dynamometer, a baseline comparison measuring instrument. Also, the plasma-assisted poling process that potentially increases piezoelectricity was briefly introduced and discussed with a preliminary result. As a result, this study promises new multi-functional materials, novel designs, and approaches in a single AM and fabrication step by combining AM with piezoelectric polymer poling methods in convenient, fast, and precise manner.

A comprehensive study relevant to displacement sensing techniques based on optical edge-diffraction has been first introduced in academic society. Dimensional sensors with nanometer resolution are key components of many precision imaging, positioning, and fabrication machines. Knife-edge techniques are commonly used for optical beam profiling of laser beams, but edge-diffraction sensing techniques for dimensional metrology was first introduced in 2006 and have been used for many dimensional metrology applications. This review paper outlines the computational approaches for optical edge-diffraction analysis and the case study for various displacement measurement applications. This review is the first report that summarizes literature relevant to displacement sensors based on optical edge-diffraction and discusses how optical edge-diffraction techniques enhance dimensional metrology in terms of accuracy, precision, sensitivity, bandwidth, and uncertainty. In addition, future applications for employing edge-diffraction techniques will be further discussed and highlighted.

The dimensional measurement technique utilizing curved-edge diffraction is applied for the dynamic system identification of precision spindle system. Both static and dynamic behavior including stiffness, damping ratio, and parasitic motion of a precision ball bearing spindle system is characterized by impact response, while the spindle displacement is measured with the curved-edge-type sensors (CES). The CES effects of spindle radius and surface quality were theoretically and empirically investigated. The capacitive-type sensors (CS) were used for a baseline comparison with the CES outputs. Unlike CS, CES is not sensitive to the spindle radius, surface quality, and coupling motions, shows high bandwidth and low noise, and allows for the dimensional measurement at a localized area. These results indicate that CES can be a good alternative to CS for spindle metrology. In the experiment, natural frequency (56 Hz (linear) and 680 Hz (angular)), stiffness (460–790 N/µm) and damping ratio (0.04–0.08) of precision spindle system were measured by CS and CES at the same time. The dynamic model of ball bearing spindle system was also discussed.

This paper represents a novel approach capable of in-process damping parameter control for nanopositioning systems by implementing a fluidic pressure-fed mechanism (FPFM). The designed internal fluidic channels inside the nanopositioning stage fabricated by a metal additive manufacturing process can be filled with various fluids such as air, water, and oil and pneumatically or hydraulically pressurized. The damping was experimentally characterized with respect to fluids and corresponding pressure level (80 psi, which was the maximum safe operating pressure in the current laboratory setting) through a free-vibration test, hammering test, and sine input sweeping test in open-loop and closed-loop positioning control conditions. As a result, the FPFM revealed the following characteristics: (1) damping increases when the internal fluidic channels filled with fluids and pressure level at 80 psi, (2) the dynamic system showed the highest damping when the water exists in internal channels, and (3) the existence of fluids and certain pressure in the fluidic channel does not have a negative influence on the motion quality and positioning control while the nanopositioning system is in operating. Additionally, the tracking error was reduced by FPFM. It is expected that the FPFM method will be utilized for vibration and noise control applications for high precision dynamic systems.

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 × 10 − 4 / µ m with respect to edge roughness change. Experimental results showed a good agreement with computational results.

This paper presents a novel thickness profile measuring system that measures double-sided thin pipe wall surfaces in a non-contact, continuous, cosine error-free, and fast manner. The surface metrology tool path was developed to align the displacement sensors always normal to the double-sided surfaces to remove cosine error. A pair of capacitive-type sensors that were placed on the rotary and linear axes simultaneously scans the inner and outer surfaces of thin walls. Because the rotational error of the rotary axis can severely affect the accuracy in thickness profile measurement, such error was initially characterized by a reversal method. It was compensated for along the rotational direction while measuring the measurement target. Two measurement targets (circular and elliptical metal pipe-type thin walls) were prepared to validate the developed measurement method and system. Not only inner and outer surface profiles but also thin-wall thickness profiles were measured simultaneously. Based on the output data, the circularity and wall thickness variation were calculated. The thickness profile results showed a good agreement with those obtained by a contact-type micrometer (1-µm resolution) at every 6-deg interval. The uncertainty budget for this measuring system with metrology tool path planning was estimated at approximately 1.4 µm.

This paper represents the development of a synchronous thickness profile measurement system that measures double-sided thin pipe wall surfaces in a non-contact, continuous, cosine error-free and fast manner (NCCCE-Fast double-side thickness profiles measurement). A pair of capacitive type sensors (CS) placed on the rotary and linear axes scan the inner and outer surfaces of the thin wall. Surface metrology tool path is developed to align the displacement sensors always normal to the double-sided surfaces simultaneously. Because the rotary axis’s rotational error can badly affect thin wall thickness profile measurement accuracy, such error is initially characterized by a reversal method and was compensated for along the rotational direction while measuring the sample. Two measurement target samples (round/oval metal pipe-type thin walls) are prepared. Not only inner/outer surface profiles but also thin wall thickness profiles are obtained. Based on the output data, the circularity and ovality can be calculated, and those results are compared with those obtained by a contact type micrometer at every 6 degrees interval. As a result, the developed thin wall thickness profilometer can provide high precision results, continuous and fast thickness profile scanning and data are acquired for visualization.

This paper presents a novel method to eliminate cosine error in precision concave and convex surface measurement by integrating a displacement probe in a precision spindle. Cosine error in surface profile measurement comes from an angular misalignment between the measurement axis and the axis of motion and negatively affects the measurement accuracy, especially in optical surface measurements. A corrective multiplier can solve this problem for spherical surface measurement, but cosine error cannot be eliminated in the case of complex optical surface measurement because current tools do not measure such surfaces along the direction normal to the measurement plane. Because the displacement probe is placed on the spindle axis, the spindle error motion will affect the shape precision and surface roughness measurement of optical components such as mirrors and lenses, and the displacement probe will measure a combination of the spindle error motion and the geometry of optical surfaces. Here, the one-dimensional concave, convex, and hollow measurement targets were used, and cosine error was fundamentally eliminated by aligning the probe on the spindle always normal to the measured surface, and compensation was made for the aerostatic bearing spindle rotational error obtained by the reversal method. The results show that this proposed measurement method cannot only eliminate cosine error but also scan the large area quickly and conveniently. In addition, measurement uncertainty and further consideration for future work were discussed.

We present a feature-selective segmentation and merging technique to achieve spatially resolved surface profiles of the parts by 3D stereoscopy and strobo-stereoscopy. A pair of vision cameras capture images of the parts at different angles, and 3D stereoscopic images can be reconstructed. Conventional filtering processes of the 3D images involve data loss and lower the spatial resolution of the image. In this study, the 3D reconstructed image was spatially resolved by automatically recognizing and segmenting the features on the raw images, locally and adaptively applying super-resolution algorithm to the segmented images based on the classified features, and then merging those filtered segments. Here, the features are transformed into masks that selectively separate the features and background images for segmentation. The experimental results were compared with those of conventional filtering methods by using Gaussian filters and bandpass filters in terms of spatial frequency and profile accuracy. As a result, the selective feature segmentation technique was capable of spatially resolved 3D stereoscopic imaging while preserving imaging features.

This paper presents a non-contact, convenient, efficient cutting tool wear monitoring technique of dicing wheel based on an edge diffraction effect. Dicing is a standard technology for fabricating components of micro-electromechanical systems, and the wear of dicing wheels may influence the components’ quality with respect to cutting-surface quality and subsurface damage. Based on the edge diffraction principle that utilizes interference of transmitted wave and a diffracted wave at the wheel end, the diffraction patterns according to dicing wheel conditions were scanned, and cross-correlation was used to extract attrition and abrasive wear from the measured diffraction patterns. Attrition and abrasive wear were related with lag and similarity coefficients of cross-correlation, respectively. This measurement technique can be used for on-machine or in-process monitoring of wheel conditions or wheel radius compensation and can be included in dicing parameter optimization process.

X-ray computed tomography (CT) is uniquely suited for dimensional measurement of components having internal geometry, difficult-to-reach part features, and easy-to-deform or flexible structures. Through the development of standards it is also becoming accepted as a metrology tool. The objectives of this study are to compare dimensional measurements on artifacts containing internal structures and mechanically compliant features using current state-of-the-art CT and coordinate measure machine (CMM) techniques. It also aims to discuss some of the issues with recently developed standards for CT measurement uncertainty estimation. To illustrate the challenges of CMM and the potential of X-ray CT for reliable dimensional inspection, two different problems are presented: 1) characterization of internal geometry in a metallic artifact that has features inaccessible to tactile or vision-based measurement techniques; and 2) evaluation of dimensional measurement of diameters, form, and relative distances in the components of a flexible object with stems that bend due to mechanical contact by tactile instruments, e.g., CMM. In addition, some issues with the direct application of the ISO 15530 series for the estimation of CT measurement uncertainties are discussed, and a generalized formalism for uncertainty budgeting in CT metrology (still based on the ISO 15530 guidelines but with some differences) is applied to the measurements presented throughout this paper. For dimensions of geometric features ranging from 0.6 mm to 65 mm, a comparison between CT and CMM measurements typically resulted in differences of approximately 5 μm or less for most of the measurements, while expanded uncertainties computed for the CT measurements ranged from 1 to 20 μm. CT measurements on the internal geometries resulted in uncertainties comparable to CMM data that were obtained with the metallic artifact disassembled. However, in the particular case of measuring compliant structures, the conventional CMM strategies led to large systematic errors in the measurements. It is demonstrated that using extrapolation methods, measurements from these two systems converged to within ±2 μm.

This paper introduces an optical measurement technique to enhance knife-edge interferometry (KEI) for edge topography characterization with a high resolution by shaping a beam of light incident on the sharp edge. The enhanced KEI forms spherical wavelets as a new light source by focusing a beam before the sharp edge by using an objective lens, and those wavelets interfere with the secondary wavelets diffracted at the sharp edge along the propagation direction. Unlike a conventional KEI that is limited to low spatial resolution due to a relatively large beam diameter, the enhanced KEI can increase the fringe spatial frequency and produce more data necessary for fringe analysis toward edge topography characterization. Edge samples with various edge conditions were used for validation. As a result, the enhanced KEI improved the resolution of edge topography characterization compared to the conventional KEI. This study has the potential to be utilized in high-resolution optical microscopy for edge topography characterization.

This paper presents a novel technique for more easily measuring cutting tool wear using knife-edge interferometry (KEI). Unlike an amplitude splitting interferometry, such as Michelson interferometry, the proposed KEI utilizes interference of a transmitted wave and a diffracted wave at the cutting tool edge. In this study, a laser beam was incident on the cutting tool edge, and the photodetector was used to determine the interference fringes by scanning a cutting tool edge along the cutting direction. The relationship between the cutting tool wear and interferometric fringes generated by edge diffraction phenomena was established by using the cross-correlation of KEI fringes of two different cutting tool-edge conditions. The cutting tool wear produced the phase shift (attrition wear) and the decay of oscillation (abrasive wear) in the interferometric fringe. The wear characteristics of the cutting tool with a radius of curvature of 6 mm were investigated by measuring the interferometric fringes of the tool while cutting an aluminum work piece in a lathe. As a result, the attrition and abrasive wear of cutting tool showed a linear relationship of 5.62 lag/wear (μm) and 1.14E-3/wear (μm), respectively. This measurement technique can be used for directly inspecting the cutting tool wear in on-machine process at low-cost.

We analyzed the parameter effects of an optical knife-edge sensor (OKES) and the measurement uncertainty to achieve high linearity, long range, and high accuracy for nanopositioning stage applications. The OKES utilizes interference fringes produced from diffraction across the knife-edge. The total field at the detector was calculated from superposition of the incident field and the diffracted field at the knife-edge, and the edge diffraction effects on the sensor design parameters (distance between the knife-edge and detector, wavelength and beam diameter) were investigated by using a design of experiment (DOE), 3-Level L 9 matrix from the Taguchi Method. Multi-factor experiments were designed to determine the relationship between factors affecting the interferogram and the sensor linearity. It was found that a shorter knife edge-detector distance, shorter wavelength, and larger beam diameter show high signal-to-noise ratio for sensing linearity. The OKES was modeled by using the electromagnetic wave propagation principle, and it was experimentally verified by controlling the positioning of an XY nanopositioning stage by the OKES. The sensor noise level showed X 20.1 nm and Y 19.4 nm, and the fundamental sensing limits of the OKES were estimated to be X 0.19 nm/ Hz and Y 0.23 nm/ Hz for a ±1.0 mm working range. These results indicate that the OKES can be a good alternative to other precision metrology tools because of its large working range, positioning accuracy, resolution, linearity, and bandwidth, as well as its compact size and low cost.

We proposed a novel optical technique to monitor miniature spindle runout in a simple manner. Miniature spindles are commonly used in many machining applications, for example: micro-milling and micro-grinding. However, the capacitive sensors (CS) or eddy current sensors typically used for spindle runout measurements cannot be used for miniature spindle systems. This is due to the nonlinearity of the charge between a curved surface and a flat plate (sensing area) and a curved surface (measuring target area) and the effective sensing area being larger than the measuring target area. The proposed sensor utilizes curved-edge diffraction (CED), which uses the effect of the cylindrical surface curvature on the diffraction phenomenon in the transition regions adjacent to shadow, transmission, and reflection boundaries. The laser beam is incident to the spindle shaft edges along the Y and Z axes, four photodetectors then collect the total fields produced by the interference created by the waves due to CED around the spindle shaft edges. Two CS were used as a baseline comparison with the proposed sensor’s performance. A spindle with a shaft diameter of ϕ 5.0 mm (same as CS effective sensing area) was selected to compare the results of the curved-edge sensor (CES) with the results of the CS. The spindle runout was measured and the following results were found: CES-CS calibration nonlinearity (Z 0.35% and Y 0.40%) and resolution (Z 20.1 nm and Y 26.0 nm for CS and Z 20.3 nm and Y 15.9 nm for CES). The fundamental sensing limit of CES was estimated to be: Z 0.52 nm / Hz and Y 0.41 nm / Hz for a working range of approximately 100 μm, respectively.

This paper presents dynamic characteristics of pressure-fed flexure mechanisms with the additively manufactured internal fluidic channels. Additive manufacturing (AM) technology makes use of the mechanical design flexibility that can effectively control the material distribution in terms of stiffness and damping of the flexures. Five different fluidic channel geometry (circular, semicircular, inverse-semicircular, triangular, and inverse-triangular) with the same cross-sectional area was designed and fabricated inside of one-dimensional cantilever beam (10 × 30 × 100 mm3). Stiffness, damping ratio and natural frequency of each cantilever according to varying air pressure condition from 14.7 psi (atmospheric pressure) to 75 psi were characterized, and at the same time dynamic behaviors of each cantilever were identified by using dynamic signal analyzer. In addition, dynamic characteristics of water-filled flexure mechanism were compared to those of air-filled cases. As a result, the internal channel geometry and filled-in media in the channel have significant influences to determine dynamic characteristics of flexure mechanisms. Such pressure-fed mechanisms can be considered in the first stage of AM flexure design and fabrication processes to adaptively control dynamic behaviors in an easy, convenient and low-cost manner.

This paper presents cross-coupling effect of a polymer-based large range XY nanopositioner fabricated by an additive manufacturing (AM) process, stereolithography. The flexural properties were preliminary characterized to design the XY stage capable of ±1.0 mm range motion. The voice coil motors were aligned along the moving axes of the stage, and optical knife edge displacement sensors were placed at the center of the stage without Z -axis offset distance perpendicular to the moving axes to mitigate Abbe error and minimize cosine error. The cross-coupling of AM stage was 3.4% and 8.1% for XY and YX axes that is relatively larger than the value 1.0% estimated by the finite element method. It was considered to be responsible for AM fabrication tolerance or local irregularity in material properties because those properties are highly dependent on curing temperature and time even though the stage is fabricated layer-by-layer under the identical condition. The AM stage thus should be positioning feedback-controlled to avoid cross-coupling effect. As a result, the root-mean-square radial trajectory error was 3.62 μm under radius 1.0 mm and 1 Hz circular motion condition. These results indicated that the AM stages can be used for large range nanoprecision applications such as scanning, lithography, or fiber-optics alignments.

This paper presents a non-contact, convenient, efficient cutting tool wear monitoring technique of dicing wheel based on a knife-edge diffraction interferometry. Dicing is a standard technology for fabricating components of micro-electromechanical systems, and the wear of dicing wheels may influence the components’ quality with respect to cutting-surface quality and subsurface damage. Based on the edge diffraction principle that utilizes interference of transmitted wave and a diffracted wave at the wheel end, the diffraction patterns according to dicing wheel conditions were scanned, and cross-correlation was used to extract attrition and abrasive wear from the measured diffraction patterns. Attrition and abrasive wear were related with lag and similarity coefficients of cross-correlation, respectively. This measurement technique can be used for in-process monitoring of wheel conditions or wheel radius compensation and can be included in dicing parameter optimization process.