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Polycrystalline diamond (PCD) has excellent properties such as high hardness, high chemical inertness, high wear resistance and a low friction coefficient. Thus, it has been expected to be applied to used in various mechanical parts such as sliding parts. However, diamond is difficult to machine owing to its high hardness and chemical inertness. Therefore, a highly efficient and high-quality machining process is required for PCD. In this study, the authors developed fixed abrasive polishing tools for the mirror-like surface finishing of PCD that contain mechanochemical abrasive grains with diamond grains. As a result of fixed abrasive polishing experiments, it was clarified that a mirror-like surface can be obtained by fixed abrasive polishing using a tool containing SiO2 and diamond abrasives. Moreover, it was found that the removal efficiency can be increased under a high-temperature condition.

To help reduce the environmental impact of abrasive polishing, we have investigated the use of a compact robot and fixed-abrasive polishing. We used a five-joint closed-link compact robot with a fine diamond stone on its main axis to polish the glass plate and measured the polishing pressure(=pressing force/stone constant area), the polishing force, and the material removal rate. From these results, we investigated the relationship between the polishing pressure and the polishing force and between the polishing pressure and the material removal rate. We found that there is an interesting relationship between the polishing pressure and polishing force, which is not simply proportional but exponential, that the friction coefficient(=polishing force/pressing force) increases as the polishing pressure increases, and that by focusing on the friction coefficient, we can estimate the material removal rate.

Rising demand for sustainable development motivated our eco-friendly polishing method. In this study, fixed-abrasive polishing using a compact robot was proposed based on a new approach that includes the idea of secondary tools. The effectiveness of using a compact robot was investigated by life cycle assessment for eco-friendly polishing processing. The actual polishing process was carried out with low pressure to determine the potential of the proposed polishing method. As a result, low-environmental-load processing was achieved by machine downsizing without affecting the processing results by designing an independent pressure mechanism along the equipment’s main axis. The nano-surface could also be obtained with this method for glass material.

In super-finishing by cubic boron nitride (CBN) stones, it is considered that chips are formed by crossing of grain loci. Thus, crossing angles of grain loci are paid attention to as an important parameter. In this paper, the new method for prediction of cutting performance is proposed using average crossing angle of grain loci. On the other hand, chip formation process is classified into two types. Therefore, all crossing angles are calculated after considering these types of crossing of grain loci. Average crossing angle is defined as the mean value of those. Moreover, the relation between these average crossing angle and cutting performance is investigated by various calculations and experiments. As results, average crossing angle is one of the most important parameters to estimate the cutting performance on super-finishing using CBN stones.

One of the goals of this study is to obtain nano-mirror surfaces on SUJ2 (J IS) hardened steel. We clarified the causes of drop-out of abrasive grains that increase surface finish (roughness), paying attention to the crossing angle between abrasive grain paths. We have developed an ultra-low-pressure method for obtaining a finer finish in super-finishing using vitrified bonded cubic boron nitride (cBN) abrasive stones. This is a finer finish with very little or no stock removal, less than ordinarily occurs in a conventional process using aluminum oxide or silicon carbide stones. We have fabricated a prototype super-finishing machine that provides stable ultra-low pressures by means of an air slide. Super-finishing was attempted using ultra-low pressures (less than 0.1 MPa) with cBN abrasives averaging less than 8 mum in diameter. As a result, super-finishing with a processing pressure of 0.02 MPa could be achieved using fine-grit cBN. The study demonstrated that a surface finish on the nano-order can be obtained under ultra-low-pressure conditions.

In this Paper, laser cutting of super abrasive thin stick stone (SATSS) whose grains are CBN and diamond usingNd:YAG laser is studied. We have investigated cutting characteristics of SATSS and strength of the heat affected zone(HAZ) on the surface cut with laser. As a result, SATSS of 3mm in thickness can be cut off with the width of 0.2mm inmaximum, and there is no chipping at the edge of the surface cut with laser. In the case of CBN stick stone, cutting timewith laser is 2.5 times faster than that with diamond blade, and 15 times faster in the case of diamond one. There is aHAZ with a thickness of 0.05mm. In this HAZ, the abrasive grains are oxidized and their crystal structures are changedby the heat of laser irradiation. However, laser is absorbed effectively by the HAZ, and the HAZ raises the strength ofSATSS because the pores inside of the HAZ are closed by the re-solidified vitrified bond. From these results, it is shownthat laser cutting can apply to the manufacturing ofthe SATSS and improve the productivity and the quality.Keywords: pulsed Nd:YAG laser, super abrasive thin stick stone, CBN stick stone, Diamond stick stone, cut-off charac-teristic, absorption characteristics, heat affected zone