Ryunosuke Sato

Development of Ultrafine-Crystalline cBN Abrasive Grains for Innovative Grinding Technology

This paper presents some mechanical properties and grinding characteristics of newly developed ultrafine-crystalline cBN (UcBN) abrasive grains. This new UcBN grain possesses an ultrafine crystal structure composed of sub-micron sized primary crystal grains. The fracture strength of the UcBN grain is about 1.5 times higher than that of conventional polycrystalline cBN grain. The grinding ratio in grinding with the UcBN grain is 4–10 times higher than those in grinding with conventional typical monocrystalline and polycrystalline cBN grains. Therefore, the UcBN abrasive grain has an enough ability to innovate the grinding technology.

Polishing Characteristics of CMP for Oxygen Free Copper with Manganese Oxide Abrasives

A series of polishing experiments have been carried out using Mn2O3 as abrasive grains to examine the polishing characteristics of CMP for oxygen-free copper. It has been found that the polishing rate increases as the polishing speed and/or polishing pressure increases, also the role of polishing speed on the polishing rate is more significant than that of the polishing pressure. The effects of the polishing conditions are however small, when polishing a finished surface roughness of about Ra 5 nm. A long polishing time, with an approximately constant polishing rate, can be achieved, without dressing, with a polishing pressure P = 9.4 kPa. It was found that higher polishing pressures could achieve a higher polishing rate, however the polishing pressure would decrease as the polishing time increased.

Evaluation of positioning performance of a fine-coarse mechanism

A new positioning system has been developed to realize both the fine motion and the coarse motion independently and/or simultaneously to reduce the positioning time with guaranteeing positioning accuracy. A conventional speed reducer unit is utilized to cope with this problem in this study. The combination of reducer and overdrive enables to position the end effector with accurate and rapid. This fine-coarse motion of the developed system is realized by only commercial-release parts consisted of two stepping motors and speed reducer aligned in an axis. The main advantage of this mechanism is that there is no stroke limitation in fine and coarse motions compared with the conventional fine-coarse motion stage by usage of PZT device. The basic performances are evaluated by adopting the feedback positioning control in this report. The developed positioning system demonstrates the efficient performance with accurate and rapid positioning.

Fractal Analysis of Self-Sharpening Phenomenon in cBN Grinding

This paper presents a fractal analysis of the self-sharpening phenomenon of the grain cutting edges in cBN grinding. To clarify the self-sharpening mechanism due to the micro fracture of the cutting edges, the changes in three-dimensional profile of the cutting edges in the grinding process have been measured using a scanning electron microscope with four electron probes and evaluated on the basis of the fractal analysis. The fractal dimension for surface profile of the cutting edge formed by the micro fracture is higher than that of the cutting edge formed by the ductile attritious wear. Therefore, the complicated changes in shape of the cutting edge due to the self-sharpening can be evaluated quantitatively using the fractal dimension.

Affected layer evaluation of ultraprecise machined surface using magnetic force microscopy

This paper describes a new method for evaluating the affected layer of ultraprecise machined surface based on the magnetic domain analysis using a Magnetic Force Microscope (MFM). The fine maze magnetic domain pattern is observed on the ultraprecise lapped ferrite (111) plane. The maze domain pattern becomes coarser by increasing the etched depth of surface affected layer. The area percentage of magnetic domain pattern in the whole machined surface decreases with increasing the etched depth of the affected layer and the magnetic domain pattern disappears when the etched depth exceeds about 1 µm. This critical value in the etched depth is almost equal to the surface affected layer depth, evaluated from electron diffraction analysis. These results show that the magnetic domain imaging method using MFM becomes a useful technique of evaluating the surface affected layer of various magnetic materials.

Evaluation of Angular Error of Fine-coarse Motion Driving Mechanism

A new positioning system has been developed to realize both the fine motion and the coarse motion independently and/or simultaneously to reduce the positioning time under the limitation of guaranteeing the positioning accuracy. To cope with this problem, a new combination of positioning methods been proposed. The fine-coarse motion of the developed system is realized by only commercial-release parts consisted of two stepping motors and harmonic drive reducer aligned in an axis. The main characteristic is that there are no stroke limitations in the fine and coarse motions with respect to the conventional fine-coarse motion stage by usage of PZT device. The basic performances were evaluated by adopting the open loop positioning and the feedback positioning. The developed positioning system demonstrates the efficient performance of the accurate and rapid positioning

Measurement and vibration control of dynamic characteristics of feed table for machine tool

Vibration control of feed table on NC positioning control is one of the most important problems in machine tools, because the amplitude of vibration itself causes the degradation of machined profiles and surface roughness. Previous studies looked at the low frequency range in which conventional NC feed table responds and deal with the vibration problem while positioning. Another vibration problem exists in the range of higher frequency. The phenomenon is often caused by the rigidity of ball-screw driving mechanism. Therefore, conventional vibration control method by computing input command that compensates the positioning accuracy is not to be adapted. The exclusive passive damper is designed based on the measurement results of dynamic characteristics on the positioning system and developed in order to solve this problem. The effects of the damper are reported with experimental testing and calculation results of the parameters.

Mechanical Properties and Grinding Characteristics of High Purity Polycrystalline CBN Grits

Some mechanical properties and grinding characteristics of newly developed high purity polycrystalline cBN grits have been investigated. This new cBN grit possesses an ultrafine crystal structure composed of sub-micron sized primary crystal grains. It also has a fracture strength 1.5 times higher than the conventional polycrystalline cBN grit. When grinding high-speed tool steel, the grinding ratio in using the new type cBN grits is 6 times higher than that in using the conventional polycrystalline cBN grits.