To monitor the stirring state by on-line estimation of liquid viscosity instead of stopping the stirring process and measuring the viscosity using viscometer, a basic study clarifying the effect of stirring conditions was carried out. For this purpose, the relationship between liquid viscosity and the stirring conditions, such as stirring torque, stirring speed, the duty ratio of PWM, impeller and beaker type, and the blade position in the beaker was analyzed. The second-order relationship between the stirring speed and torque, the linear relationship between viscosity and torque, and the linear relationship between duty ratio of PWM and stirring speed were observed, thereby indicating that the liquid viscosity could be estimated by an experimental formula based on the duty ratio and the stirring speed. In addition, the type of impeller and beaker was identified using the magnetic field inside impeller and RFID technology. For reducing the error in calculating the liquid viscosity, the employment of an impeller blade with a large rotational resistance and stirring with the blade at the center zone of the beaker were found to be necessary.

To identify the impeller types automatically for an overhead stirrer operation, a digitalization of the analog magnetic signal of the permanent magnet arrays was performed. The permanent magnets were installed into the impeller shaft in NS-SN array, and their magnetic fields were measured by a hall sensor while the impeller was mounted on the stirrer. Results of the experiments and finite element analysis showed that the number of peaks of magnetic field signal was observed corresponding to the number of magnets. Considering the consistency of the number and the magnitude of magnetic field peaks, it was found to be more advantageous to measure the magnetic field in the axial than in the radial direction of the impeller. For eliminating the influence of the noise included in the analog signal and connecting it with the micro-controller of the stirrer, the analog magnetic field signal was transformed to the digital-pulse-patterned signal through DC offset, amplification, absolute value, and the comparator circuit. Through these processes, the error in identifying the impeller type could be significantly reduced compared with directly using the magnitude of the analog magnetic signal.

Vibration assisted cutting (VAC) is one of the promising methods for precision machining, which has been normally equipped with piezoelectric materials. In this paper, a feasibility of applying magnetostrictive materials to VAC as a cutting device instead of piezoelectric materials was studied. For this, the vibrational characteristics of a magnetostrictive material was investigated with respect to a coil design, a preload, and the effects of a biasing and an exciting magnetic fields. The output strain of a magnetostrictive material is restricted due to an increasing inductive impedance as the exciting frequency increases and the heat of coil, etc. Through the experimental results, it was found that the biasing and the exciting magnetic field affected the output performance significantly but not the preload. In conclusion, the magnetostrictive material could be used only in the low frequency range but not a good candidate for high frequency actuating application.

In ultra precision machining, it is necessary to adjust the horizontality and reference position of a workpiece in a noncontact manner. For this, a simple process by measuring impedance between a tool tip and a workpiece which are connected to impedance analyzer is proposed. As the distance between the tool and the workpiece gets closer, the reduction rate of impedance becomes higher over all frequency ranges. By setting threshold value of impedance reduction rate at specific frequencies through preliminary experiments, the distance between the tool and the workpiece can be predicted and it directly enables us to horizontalize the workpiece and to set the tool to the desired reference position.

In elliptical vibration cutting (EVC), cutting performance is largely affected by the shape of an elliptical path of the cutting tool. In this study, two parallel piezoelectric actuators were used to make an elliptical vibration cutting device. When harmonic voltages of 90° out-of-phase are supplied to the EVC device, creation of an ideal elliptical trajectory whose major and minor axes are parallel to the cutting and thrust directions is anticipated from a kinematic analysis of the EVC device, however, the paths we experimentally observed showed significant distortions in its shape ranging from skew to excessive elongation of the major axis of the ellipse. To compensate distortions, an analytical model describing the elliptical path of the cutting tool was developed and verified with experimental results, and based on the analytical model, the distorted elliptical paths created at 100 ㎐, 1 ㎑, and 16 ㎑ were corrected for skew and elongation.

Ultra-precision turning is highly needed to manufacture molds for precision lens. In this study, micro-turning combined with elliptical vibration cutting (EVC), which is known to enhance micromachining quality, was investigated by installing a rotary stage into the micro-grooving machine. From machining experiments involving materials of copper, brass, and aluminum and single and poly crystalline diamond tools, it was found that EVC produced thinner and curlier chips and that better surface finish could be achieved, compared with conventional turning, owing to prohibition of formation of burrs and built-up edges. Therefore, we found EVC micro turning could be readily utilized to manufacture precision mold.

Successive micro-scale V-grooves and a grid of pyramids were machined by elliptical vibration cutting (EVC) to investigate feasibility of using EVC as an alternative method of creating micro-molds to photo-lithography and electroforming, which have been commonly employed. An elliptical vibration grooving machine was developed which consists of two orthogonally-arranged piezoelectric actuators, a diamond cutting tool, and a motorized xyz stage. The micro-scale features were machined on materials of copper, duralumin, nickel, and hastelloy and it was found that EVC significantly reduces cutting resistance and prohibits generation of side burrs and rollover burrs, thus resulting in improving machining quality of micro-molds in all experimented workpiece materials.

A cutting device capable of generating various shapes of the cyclic elliptical trajectory of a cutting tool was proposed and micro v-grooving experiments were performed to investigate the characteristics of elliptical vibration cutting(EVC). The proposed cutting device is comprised of a pair of parallel piezoelectric actuators with which harmonic voltages of varying phase difference and magnitude are supplied, creating various shapes of the elliptical tool path. The attributes of the elliptical locus involving the direction of the axis of an ellipse, the rotational direction and amplitudes of a trajectory were fine-tuned for stable operation of the EVC. The EVC characteristics performed with brass and copper revealed reduction in the cutting resistance and suppression of burr formation, resulting in the enhancement of form accuracy of machined micro- features. While the effect of the EVC increases with the increase of excitation frequency and the amplitude, it is found that a change in the cutting force decreases as the amplitude of an elliptical locus increases.

In metal casting process, it is very difficult to predict the form accuracy of cast part and reduce repeatability error. In this study, the variations of form accuracy were measured in the process of metal cast prototyping, where RP part is manufactured from CAD model in the first, and then, wax part is cast in the vacuum environment using the RP part as master model, and finally metal prototype is cast using ceramic mold and the wax part as pattern. To investigate the variations of form accuracy, the averages and standard deviations of error distribution of the parts measured by 3D scanner were compared. It was observed that the biggest shrinkage is generated during the extraction of wax part in the second step and the biggest deterioration ofform accuracy is generated during the metal part casting in the last step.

Among various rapid prototyping processes, stereo-lithography process which can manufacture transparent prototype is known to be the greatest in the form & dimensional accuracy and surface roughness. In this paper, bench mark tests of 4 stereo-lithography-type rapid prototyping apparatus were carried out using transparent materials. The test includes measurement of mechanical properties, form accuracy, building speed and manufacturing cost. It was observed that ViperPRO of 3D systems is advantageous in the mechanical properties and building speed, RM6000l/ of CMET in sub-milli scale form accuracy and manufacturing cost, and relatively economical Eden500V of Objet is great in tensile strength at room temperature.

FDM, SLS, and EOS processes are the layered manufacturing processes for functional prototypes. In this paper, bench mark tests of those processes were carried out using various materials. The test includes mechanical properties, such as tensile and compressive strengths, hardness, impact strength, and heat resistance, and surface roughness, shape and dimensional accuracy, manufacturing time, and manufacturing costs. It is verified that SLS method is advantageous in surface roughness and manufacturing time, EOS method in shape accuracy, and FDM method is great in manufacturing costs.

For precise micro-grooving and surface machining, a mechanism for creating elliptical vibration cutting (EVC) motion is proposed which uses two parallel piezoelectric actuators. And based on its kinematical analysis, variations of EVC path are investigated as a function of dimensional changes in the mechanism, phase difference and amplitude of excitation sinusoidal voltages. Using the proposed PZT mechanism, various types of two dimensional EVC paths including one dimensional vibration cutting path along the cutting direction and thrust direction can be easily obtained by changing the phase lag, the amplitude of the piezoelectric actuators, and the dimension of the mechanism.

For precise micro V-grooving, ultrasonic elliptical vibration cutting (UEVC) is proposed using two parallel piezoelectric actuators, which are energized by sinusoidal voltages with a phase difference of 90 degrees. Experimental setup is composed of stacked PZT actuators, a single crystal diamond cutting tool, and a precision motorized xyz stage. It is found that the chip formed in the process of UEVC is discontinuous because of the periodic contacts and non-contacts occurring between the tool and workpiece. It is experimentally observed that the cutting force in the process of UEVC significantly reduces compared to the ordinary non-vibration cutting. In addition, the creation of burr during UEVC is significantly suppressed, which is attributable to the decrease in the specific cutting energy.

The Classification of defected oil-seals using a vision system with the artificial neural network is presented. The artificial neural network for classification consists of 27 input nodes, 10 hidden nodes, and one output node. The selection of the number of the input nodes is based on an observation that the difference among the defected, non-defected, and smeared oil-seals is greatly pronounced in the 26 step gray-scale level thresholding. The number of the hidden nodes is chosen as a result of a trade-off between accuracy and computing time. The back -propagation algorithm is used for teaching the network. The proposed network is capable of successfully classifying the defected from the smeared oil-seals which tend to be classified as the defected ones using the binary thresholding. It is envisaged that the proposed method improves the reliability and productivity of the automotive vision inspection system.