Masana Kato

Modeling of Grinding Force in Constant-Depth-of-Cut Ultrasonically Assisted Grinding

This paper discusses the mechanism behind the grinding force decrease associated with ultrasonication of the grinding wheel in constant-depth-of-cut ultrasonically assisted grinding (UAG). By introducing a grinding model describing the cutting trace of an abrasive grain, an equation relating the grinding force decrease to such process parameters as the amplitude and frequency of vibration and the grinding wheel speed, is established. Experiments are conducted to confirm the theoretical prediction. Theoretical and empirical results both indicate that the decrease in grinding force is due to the grinding chips becoming smaller and fracturing more easily under ultrasonication. The results also suggest that the grinding force decrease is greater at higher vibration amplitudes and at lower grinding wheel speeds.

A New Centerless Grinding Technique without Employing a Regulating Wheel

A new centerless grinding method without a regulating wheel is pr oposed. Instead of using a regulating wheel, this method employs an ultrasonic vibrating shoe t o support the workpiece. The end of the vibrating shoe is in an elliptic motion at a high frequency, while the rotational speed of the workpiece is controlled by the elliptic motion of the shoe. An experime ntal apparatus has been designed and constructed. Tests involving the rotational drive of a workpiec e were then conducted on the apparatus, which showed that the workpiece rotational speed depends on the AC voltage and the frequency. Finally, grinding tests involving pin-shaped workpieces with an initial roundness of 20 μm were performed. The results show that the roundness of the workpieces w as improved to 1.5 μm after grinding using the new apparatus.

Effects of Ultrasonic Vibration in Truing and Dressing of CBN Grinding Wheel Used for Internal Grinding of Small Holes

This paper describes an experimental investigation of the effects of ultrasonic vibration in the truing and dressing of the small CBN grinding wheel used for the internal ultrasonic grinding of small holes. In the precision machining of small holes measuring several millimeters in diameter, improvement in the wheel truing accuracy is significantly levels off when using a single diamond dresser or a rotary GC wheel dresser. In the present work, a new truing and dressing technique was proposed, by which the grinding wheel is ultrasonically vibrated in its axial direction during the truing operation using a rotary GC cup dresser. In order to validate the proposed new technique, experiments were carried out. During experimental operations, the GC cup wheel was traversed along the vitrified CBN grinding wheel axis with an in-feed motion toward the grinding wheel in the wheel radial direction. The influences of the truing parameters on the truing force, the run-out of grinding wheel and the grinding wheel surface properties were investigated. As a result, it was found that applying ultrasonic vibration to the grinding wheel decreased the truing force by more than 22%, and the run-out of grinding wheel decreased from an original value of 150µm to a final one of less than 0.8µm, while that obtained without ultrasonic vibration was more than 1.1µm. As well, better surface properties of the grinding wheel were obtained by the application of ultrasonic vibration.

Determination of an Optimum Geometrical Arrangement of Workpiece in the Ultrasonic Elliptic-Vibration Shoe Centerless Grinding

This paper clarifies the influence of the geometrical arrangement of the workpiece on workpiece roundness in the ultrasonic elliptic-vibration shoe centerless grinding, and determines an optimum geometrical arrangement for minimizing the roundness error of the workpiece. The influence of the geometrical arrangements ( , , ) of the workpiece on workpiece roundness were investigated by computer simulation involving a cylindrical workpiece of 5 mm in diameter with an initial roundness error of 25 μm. The results indicated that the final roundness error of the workpiece after grinding reaches a minimum at + =7° for various values of . It was found that the smaller the blade angle , the more precise the workpiece in terms of final roundness. Practical grinding operations involving pin shaped workpieces, such as SKH51, 5 mm in diameter and 15 mm in length, were carried out on the experimental apparatus previously developed. The experimental results agreed closely with those obtained by the simulation, showing that the optimum geometrical arrangement of the workpiece can be determined at + =7° and =60°, in which the workpiece roundness was improved from an initial roundness error of 25 μm to the final one of approximately 0.6 μm.

Laser Truing and Dressing of Small Vitrified CBN Grinding Wheel

This paper aims at the development of an alterative technique for truing and dressing a small vitrified CBN grinding wheel used for the internal finishing of small holes measuring several millimeters in diameter. In conventional truing and dressing, a single-tip diamond dresser or a rotary GC cup wheel dresser is employed. This levels off the improvement in the wheel truing accuracy because the stiffness of the grinding wheel shaft with an open-sided structure is low, and the shaft is thus deformed easily due to the truing force. In the present work, a new truing and dressing technique is proposed in which a Nd:YAG laser beam is employed as the dresser. Experiments were carried out with respect to the effects of the laser beam conditions (amplitude, width and frequency of pulse, and focus offset) and the relative motion between the laser beam and CBN wheel. It was found that the run-out of the CBN wheel was decreased significantly, and the wheel surface condition was improved greatly after laser truing and dressing.

Effects of Particles Blend Ratio on Surface Quality in Surface Polishing Using Magnetic Polishing Liquid (MPL)

This paper describes an experimental investigation of the effects of the particle blend ratio on surface quality in surface polishing using magnetic polishing liquid (MPL). MPL is produced by mixing sub-micrometer- or micrometer-size abrasive particles into a Magnetic Compound Fluid (MCF), a functional fluid composed of MF(Magnetic Fluid) and MRF (Magneto-rheological Fluid), that reacts with magnetic fields. As a step toward establishing the new surface finishing technology using MPL, it is essential to clarify the effects of the blend ratio of particles to solvent in MPL. For this purpose, first five kinds of kerosene-based MPLs with different blend ratios of particles were prepared, then polishing operations involving stainless steel workpieces were carried out on an experimental rig developed in-house. During the experiments, steady state magnetic fields with different strengths were applied while the contact force between the workpiece and the polishing pad was kept constant. The experimental results showed that the blend ratio of particles affects the work-surface quality significantly. Following SEM and optical microscopy observations of the polished work-surfaces, an appropriate blend ratio, under which the surface roughness improved from the original value of Ra100nm to a final one of Ra24nm after polishing for 30min, was recommended.

A new approach to silicon wafer edge treatment by Ultrasonically Assisted Polishing (UAP)

This paper proposes a new method for silicon wafer edge treatment by Ultrasonically Assisted Polishing (UAP), in which an ultrasonic elliptic vibration polishing pad holder is employed. Thus the speed of the polishing pad relative to the wafer is increased, and a small gap is generated between the pad and the work surface so that the slurry intrudes easily into the polishing area. Experimental results showed that the wafer surface roughness and the material removal rate obtained by UAP were better by over 58% and over 24%, respectively, than those without UAP.

Energy Model in Laser Processing of a Cylindrical Grinding Wheel

Laser processing of abrasive grinding wheels is paying a great role in a truing technique to complement mechanical methods. An energy balance model was adopted that took into account the space modes of laser energy absorbed/scattered by the wheel (circular profile). Both geometric and mathematic models were developed to reveal laser processing mechanism and predict various processing parameters, such as incident position, focal offset, and incident power, to perform material removal during laser processing a cylindrical grinding wheel. Moreover, the incident angle for laser processing of small-vitrified CBN grinding wheels was optimized. Further theoretical analysis and experiments determined the focal position of the incident beam with respect to the wheel profile. Experimental studies were carried out using different processing parameters and grinding wheels to test the effects of laser space properties on processing quality. The experimental results were shown to be in reasonable agreement with predicted results.

Energy-Mode Adjustment in Laser Processing a Small Vitrified CBN Grinding Wheel

A study of the energy-mode adjustment and application was presented to investigate the effects of adjustable methods on energy mode. Three methods of energy-mode adjustment were used: by circular profile itself, by an optical scanning expander and deformable mirror. The circular profile naturally modifies energy density with the changes of incident angle. The optical scanning expander was used to turn a Gaussian beam into a uniform beam. Also a novel technique of deformable mirror was designed to obtain a more controllable energy mode for laser selective processing. Moreover, the models describing energy modes were developed to improve laser-processing performance. An experiment was arranged to simulate single-tip diamond truing and produced a result, as shown in the SEM photo, quite similar to a fine thread. The results were discussed to reveal the mechanism of laser processing.

A New Magnetic Polishing Liquid (MPL) for Precision Surface Finishing

This paper presents a new magnetic polishing liquid (MPL) produced by mixing sub-micron or micron order abrasive particles into a magnetic compound fluid (MCF) and its fundamental performance in surface finishing. MCF is an intelligent fluid, which is developed by mixing a magnetic fluid (MF) and a Magneto-rheological fluid (MRF) into a solvent, and hence reacting upon magnetic fields. In the present work, seven kinds of kerosene-based MPLs were prepared. The hydrodynamic characteristics of MPLs such as the viscosities under different magnetic fields were investigated. The obtained result indicated that the viscosity increases with the growing of the magnetic field and that the type of MPL affects greatly the viscosity. This phenomenon was discussed by observing the magnetic clusters formed in MPL. It was observed that the magnetic clusters are distributed along the magnetic fluxes. An experimental result indicated that the surface roughness varies with polishing time and gets smallest at a certain value of magnetic field strength.