Kazuhito Ohashi

Temperature distribution in a workpiece during cylindrical plunge grinding

In cylindrical plunge grinding, a large amount of heat flows into the workpiece continuously, accumulates and remains even after the process, which causes dimensional error. Therefore it is necessary to investigate the temperature distribution in the workpiece during grinding and analyze the influence of grinding heat on the dimension. Such an investigation has not been done enough, because the technology to measure the temperature distribution in the rotating workpiece has not matured. Considering such background, an in-process measuring system has been developed, which makes it possible to detect the temperature distribution in a wide range from the outer surface to the inside of the rotating workpiece. The system consists of small temperature sensors which are embedded into the workpiece, a micro computer attached on the workpiece which acquires the data from the sensors and transmits to a personal computer by a wireless communication device. Furthermore the contact type thermocouple which enables to measure the rotating surface temperature is added to the system. Measurement experiments revealed that the grinding heat conducts from the workpiece surface toward the center, accumulates, and remains in the workpiece even after the process. Heat conduction simulation was also performed. Good agreement was achieved between the simulated temperatures and experimental measurements.

Development of the Electricity Rust Preventive Machining Method in Surface Grinding

In this paper, the electricity rust preventive machining method has been developed to perfectly prevent the rust of workpiece using only the water in the surface grinding. The surface grinding can be performed under the condition of rust prevention, in which a negligible current is applied between the workpiece, connected with the cathode, and the cooling water, connected with the anode. This method can be an ultimate zero emission ecology machining, because only the water is used as the working fluid without the extreme pressure additive, the mineral oil, and the surface active agent.

Machining Characteristics of Cylindrical Blasting and Application to Micro Patterning

Micro patterning on cylindrical surface, e.g. dynamic pressure bearings, is mainly carried out by chemical etching. However, there exist environmental problems in the waste etchant processing and safety ones in works using toxic chemical liquids. On the other hands, blasting is expected as one of micro patterning methods and comes into use for not only surface modification but also machining of hard and brittle materials. The purpose of this study is to develop the micro blasting technique for cylindrical parts. Therefore, machining characteristics in blasting of rotating workpieces are experimentally investigated, analyzing the stock removal and the surface roughness. In addition, the patterning of micro herringbone grooves are carried out on spindle surfaces based on the obtained characteristics.

The Possibility of Dressless Restoration of Grindactivity in Dry Grinding of Carbon

The grinding performance of wheel remarkably decreases by the loading of wheel surface in dry grinding of hard carbon parts. In this report, we propose the removal method of loaded carbon chips in which an adhesive tape is removed with carbon chips after putting on a loaded wheel surface by an elastic roller with the setting load . The removal characteristics are experimentally investigated by analyzing the projecting height of abrasive grains, removal force of adhesive tape and so on. The removal method results in the enough projecting height of abrasive grain.

Improvement of Machining Accuracy in Micro Cylindrical Traverse Grinding

The elastic deformation of workpiece acted by grinding force is so large as to make the low machining efficiency and accuracy in the cylindrical grinding of micro parts of which the stiffness is extremely small because of their small diameter. In this study, the perpendicular axis type cylindrical traverse grinding is proposed for the manufacture of micro parts, and the undeformed chip shape in the grinding process is investigated comparing with that in the parallel axis type traverse grinding using generally for manufacture of over small-sized parts. The surface finish and the form accuracy of workpiece by the perpendicular axis type grinding are finer than those by the parallel axis type grinding with the developed micro cylindrical grinding machine.

Efficiency Investigation of Removal of Loading Carbon Chips on Wheel Surface Using Dry Ice Blasting

In dry grinding of hard carbon parts, the loading by carbon chips on wheel surface occurs in early grinding process, and the grinding performance of wheel is extremely declined. The deterioration affects the grinding accuracy and efficiency. Therefore, loading is one of the problems that must be resolved for high efficiency and high quality grinding of carbon. Generally, the grinding performance of wheel is recovered by the dressing. However, it’s not suitable from a viewpoint of the wheel life and the production cost because available abrasive grains possessing sharp edges under loading carbon chips on wheel surface are lost by dressing. In this study, we propose the dry ice blasting for removing loading carbon chips on wheel surface. The dry ice particles impact on pressed carbon chips with high pressure and sublimate to carbon dioxide quickly. Therefore, it is little influence on working environment because the dry ice doesn’t remain on wheel surfaces after blasting without the damage. In this report, we carry out the blasting tests of resinoid bond diamond wheel surface without grinding performance by loading carbon chips, and analyzed the effect of nozzle processing speed and nozzle feed pitch on recovering abrasive protrusion. The effective dry ice blasting conditions are investigated for high efficiency removal of loading carbon chips, analyzing the protrusion height of abrasive grains.

High-Efficient Regeneration of Grinding Performance Using Adhesive Films in Dry Grinding of Carbon

The grinding performance of wheel remarkably decreases by the wheel loading in dry grinding of precision hard carbon parts. When the wheel loading occurs, the dressing is carried out to remove loading chips for generation of the grinding performance. However, many abrasive grains, which have enough cutting ability under loading chips, are removed in dressing. We therefore have developed the wheel surface cleaning using adhesive films without dressing to remove loading carbon chips on wheel surfaces in our previous reports, and the cleaning could achieve the lean regeneration of grinding performance of fine grade diamond wheels. The removing ability of loading chips is improved by increasing the peeling speed of adhesive film, the pressing time of adhesive films or the number of pressing time. However the optimum cleaning condition has not been investigated. In this report, from the viewpoint of efficiency in the treatment, we therefore investigate the optimum rolling press process of adhesive film on loading disc wheel surfaces in dry grinding of carbon. The optimum treatment processes are experimentally made clear, analyzing SPa of cleaned wheel surfaces, which is one of surface roughness parameters having the correlation with the protrusion height of abrasive grains. Furthermore, the effect of the treatment on regeneration of grinding performance is experimentally verified by grinding tests of hard carbons.

Simulation Analysis and In-Process Measurement of the Workpiece Temperature Distribution in Large Surface Grinding

In surface grinding, the shape error is occurred by the thermal deformation of a ground workpiece. To finish the workpiece with high accuracy, it is necessary to understand the temperature distribution of the workpiece during grinding process. However there is no study to analyze the temperature distribution of a large workpiece during surface grinding process. In this study, an advanced simulation analysis method of the temperature distribution for a large workpiece was developed. In the developed simulation analysis method, the temperature distribution was calculated from the power consumption of the wheel motor. The power consumption can be obtained easily without any specialized equipment. To evaluate the developed simulation analysis method, in-process measurement of the temperature distribution of a large workpiece was also carried out. A large workpiece ground in this study weights about 1.3 tons. The temperature distribution was measured with thermistors mounted in many places of the ground workpiece. At the area close to the grinding surface, it was found that temperature rises immediately after the passage of grinding wheel with measuring the developed in-process measurement system. On the other hand, at the area far from the grinding point, temperature does not change quickly. The in-process measured temperature distribution agreed well with the simulated results.

Effect of dry ice blasting on removal of loading carbon chips on wheel surface

In dry grinding of hard carbon parts, the grinding performance of wheel is remarkably lost by carbon chips loading on wheel surface. The deterioration in grinding performance of wheel affects the grinding accuracy and efficiency. Generally, the grinding performance of loading wheel recovers by dressing. However, the dressing is not suitable from a viewpoint of the wheel life and the production cost because many abrasive grains having sharp edges under loading carbon chips on wheel surfaces are lost by dressing. In this study, we propose the application of dry ice blasting as a removal method of loading carbon chips. The dry ice is little influence on the working environment because of the quick sublimation of dry ice particles to carbon dioxide. In addition, the dry ice blasting might be suitable for the chip removal method because the dry ice doesn’t remain on wheel surfaces after blasting without the damage of wheel surfaces. The dry ice blasting tests of resinoid bond diamond wheel surface with no grinding performance by loading carbon chips are carried out, and the effects of dry ice blasting on removal of loading carbon chips are investigated, analyzing the protrusion height of abrasive grains, the impact pressure in the dry ice blasting and so on.

Study on the Restraint Method of Thermal Deformation in the Machine Tools

In the NC machine tools for automatic mass production processing lines, it is demanded that high stable machining accuracy is maintained for a long time. The main factor of deterioration in machining accuracy depends on the thermal deformation of machine tool, and the measures are one of the most important issues in the machine tool design. The thermal deformation is practically estimated by the temperature changing state of machine tools based on obtained data of their thermal deformation chracteristics. The estimation accuracy of thermal deformation depends on the thermometry points of machine tool greatly. This study describes an approach to the most suitable thermometry points in machine tool to determine the effective thermal deformation measures experimentally. As a result, the existence of points where the temperature of components changed with relation to thermal deformation very closely was confirmed.