This paper proposes a new optical angle sensor, in which a mode-locked laser is employed as the light source, and chromatic dispersion of a collimator objective is utilized to detect the angular displacement of a target of interest. In the proposed method, each of the optical modes in the femtosecond laser beam reflected from the reflector mounted on a target of interest is separated from the others by chromatic dispersion of a collimator objective to generate a group of focused laser beams that can be utilized as the scale for measurement of an angular displacement of the target. By detecting the change in peak frequency in optical spectra obtained by the photodetector, a small angular displacement can be measured. In this paper, as the first step of research, a prototype optical setup is developed, and some basic experiments are carried out to demonstrate the feasibility of the proposed method for measurement of angular displacement.
This paper presents a newly proposed method referred to as the femtosecond laser diffraction method for measurement of the grating period. The proposed method is established in such a way that a mode-locked femtosecond laser beam is employed as a light source for the traditional laser diffraction method, in which the Littrow configuration is utilized to evaluate grating period. Since the optical modes in a mode-locked laser, which are often referred to as the optical frequency comb, have deterministic mode frequencies with equal intervals in frequency domain, multiple diffracted beams in the same diffraction order can be obtained. By utilizing the number of Littrow angles obtained from the multiple diffracted beams in the same diffraction order, highly accurate measurement of the grating period can be expected. In this paper, as the first step of research, a prototype optical setup with a mode-locked femtosecond laser source is developed, and some basic experiments are carried out to demonstrate the feasibility of proposed method.
Machining characteristics of electrochemical machining with ultrashort pulses were investigated using numerical analysis considering the inductance of a power supply circuit. In a pulse power supply circuit of ECM, stray inductance occurs in the electric feeders. Because stray inductance influences the flow of the pulse current, the formation of the electric double layer is affected by the inductance. In order to investigate the influence of the inductance on the machining characteristics, numerical analysis was conducted considering the inductance of the power supply circuit. The electric field was analyzed by numerical simulation considering the electric double layer and faradaic current, and the circuit equation of the pulse power supply was solved considering stray inductance of the pulse power supply. Analytical results show that the inductance increases the rise time of electric current flowing through the machining gap when pulse voltage is applied. Therefore, longer pulse duration of pulse power supply is necessary to form the electric double layer when the inductance is larger. The voltage continues to be applied to the working gap even after the pulse voltage becomes low, limiting the effect of ultrashort voltage pulses due to inductance.
This paper describes the effects of preloading and ball retainer conditions of linear ball guides on a feed-drive system operating on a microscopic scale, as this is important for applications that employ linear guides in precision machines. To begin, relationships between nonlinear spring behaviors of the guide and the behavior of quadrant glitches were analyzed based on the proposed simple friction model. The behavior of the quadrant glitches, nanometer step responses, and steady vibrations were also measured for three guide conditions that differed with respect to the ball retainers and preloading. These experiments were carried out by using a special feed-drive system that comprises eight-grooved linear ball guides, an AC linear servo motor, and a linear encoder with a high position resolution of 31.25 pm. This system was set on a vibration isolation table and driven by a linear current amplifier. The time constants of each of the step responses were also analyzed based on the friction and control system model. From the analysis and experiments, it is demonstrated that the behavior of quadrant glitches and step responses are strongly influenced by the friction characteristics of the guides, and that this behavior can be adequately estimated via analysis. Additionally, it is shown that steady vibrations are also influenced by the friction characteristics, and that the amplitude of the vibration is proportional to the compliance of the nonlinear spring behavior.
Silver nanowire transparent conductive film is expected as a new material of transparent electrode, because of its superior flexibility and electrical conductivity with transparency at visible wavelength. It is essential to form insulation areas on the silver nanowire transparent conductive film in electronic circuit. Laser beam processing has been widely used for this application, since high efficiency and high quality removal is possible without mechanical contact. On the other hand, laser beam is an electromagnetic wave, and it has unique characteristics such as refraction and polarization. These characteristics have a great influence on laser-material interaction, especially in nanosize materials. However, laser processing characteristics and its mechanism have not yet been clarified. Therefore, polarization indicated by electric and magnetic fields was discussed in this study, and effects of polarization direction on removal characteristics of silver nanowire transparent conductive film by ultrashort pulsed laser with linear polarization were experimentally and numerically investigated. Removal phenomena of silver nanowire transparent conductive film by linear polarization was different from that by circular polarization. Silver nanowires arranged in the parallel direction to polarization plane were preferentially removed. In the case of crossed two silver nanowires, electromagnetic field analysis revealed that electric field intensity of silver nanowire arranged in parallel direction to polarization plane is higher than that in perpendicular direction to polarization. Therefore, silver nanowires were selectively removed depending on the polarization plane of laser beam. Electric field intensities of silver nanowire arranged in not only parallel but also perpendicular direction to polarization plane were enhanced at intersection of silver nanowires, and holes as removal marks become remarkably large at intersections of silver nanowires.
Thermal roll-to-roll nanoimprint (T-R2RNIL) using a flexible replica mold made of a special UV-curable resin was demonstrated. This UV-curable resin is able to be used for the nanoimprint process without a release agent. In this study, we examined the relationship between the hardness of the UV-curable resin and the transfer performance using flexible replica molds made of three types of UV-curable resins. The experimental result found that one special resin is a good candidate for fabrication of a replica mold for T-R2RNIL because of its high hardness and good release properties.
This work assessed the fundamental characteristics of multifunction cavitation (MFC), that was high-temperature and high-pressure cavitation, through both experimental investigations. The application of ultrasonication to the floating cavitation of a water jet was found to produce microjets containing hot spots. MFC exhibited the capacity to perform nano-level hot work at a material surface, modifying the surface morphology and the surface electrochemical condition by hot spot melting. Ultrasonic irradiation of a water jet during floating cavitation was used to generate microjets with hot spots and this MFC process was employed to perform hot work on titanium oxide (TiO2) particles as well as an ITO (Indium Tin Oxide) film on soda-lime glass and CFRP (Carbon Fiber Reinforced Plastics).
In an actively driven rotary tool, the principal cutting force and tool tangential force are measured based on the power consumption of the main spindle and the tool spindle, respectively. In rotary turning, the principal cutting force, extent of chip flow angle change, and chip thickness are typically independent of tool rotation direction either clockwise or counterclockwise. The high-efficiency reciprocating turning can be regulated such that the tool tangential force acts in direct opposition to that of the feed force. In addition, cutting scenarios where the continuous chip is broken by the chip breaker are investigated using high-speed cameras.
Directed Energy Deposition (DED) of metal materials has been widely studied with Inconel 718 using in aerospace industry. Void generation in a deposited part causes deterioration of the mechanical strength. Hence, void should be avoided in the DED process. In this study, a mechanism of void generation was investigated through the dynamic observation by high-speed camera, the thermal observation and the evaluation of the porosity. The experimental result shows that solidification time has an influence on the void generation.
In cylindrical grinding, the size accuracy of a workpiece decreases due to the thermal deformation of the ground workpiece. To improve the size accuracy, it is necessary to consider the thermal deformation of the workpiece during grinding process. In this study, we have developed an intelligent grinding system that can consider the thermal deformation of the workpiece. In this system, the thermal deformation of the workpiece during grinding process is simulated by measuring tangential grinding force. The net stock removal, that is the stock removal measured after the workpiece has been cooled, is estimated by adding the measured stock removal and the simulated thermal deformation of the workpiece. To achieve the grinding process with high accuracy, the grinding wheel is retracted when the net stock removal is reached to the grinding allowance. Using this intelligent grinding system, grinding experiments were carried out. In these experiments, the size error was reduced less than 0.3μm in radius even though the thermal deformation was more than 2μm in radius. With grinding experiments, it was confirmed that the developed grinding system could improve the size accuracy successfully.
In response to the demand for high accuracy and high resolution of angular positioning and movement of CNC machine tools, the demand for rotary encoder systems has also increased for the detection of ultra- precise angular position and movement. Authors had developed a new principle of self-calibration with multiple detecting head which enables detection of the error components of higher order with the less number of detecting heads. The system developed for this paper consists of a rotary scale with grating, sensor head unit with build-in 6 pieces of sensor heads and data processing box containing a circuit to process analog signals from the sensor head unit and output angular data applied calibration value in real time. This paper evaluates the performance of this system. In addition, the angular accuracy of the rotary encoder for servo control inside a machine tool was examined with reference to the self-calibration of the rotary encoder using the proposed method. Measured data of the accuracy of that were also utilized to generate the calibration data of the rotary encoder, and the rotary encoder was calibrated with the calibration data. The measured accuracy showed a resolution of 1/236 . It was confirmed that the angular positioning accuracy was improved because of the calibration.
Displacement sensors based on laser or optical fiber technology are recognized for their capacity for non-contact distance measurement based on reflection from an object, but with limited measurement distance and resolution. The other option could be light wave interferometer built with the mirrors on the object. However, long distance measurement requires large laser source with stabilized-wavelength. This report presents another solution: a non-contact grating interferometer displacement sensor that enables pico-meter resolution with a semiconductor laser source.