Papers by Author: Moriaki Sakakura

Abstract: In surface grinding of a large workpiece used for a sliding surface of the machine tool, high shape accuracy is required for the ground surface. Therefore, it is important to investigate the causes of the shape error observed in a large workpiece machined by surface grinding. In this study, we focused on the thermal deformation and residual stress as the causes of shape error. The in-process measurement of the workpiece temperature distribution was carried out to estimate the effect of the thermal deformation to the shape error. The estimated value of the shape error calculated from the measured temperature distribution was much less than the actual measured shape error. Therefore, the residual stress on the ground surface was measured with a portable X-ray stress measurement device. The residual stress was changed from compressed state to tensile state as the grinding pass increased. The ground shape was also deformed to concave shape as the grinding pass increased. The value of the shape error was finally reached to the constant value in several grinding conditions. From these experimental results, it is suggested that the shape error of the large workpiece is caused by the residual stress applied to the ground surface.

Abstract: 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.

Abstract: In cylindrical traverse grinding of a long workpiece with high aspect ratio, the shape accuracy of a workpiece worsens due to its low stiffness. In this study, the grinding force was measured during grinding process to calculate the elastic deformation of a workpiece caused by the normal grinding force. By comparing calculated elastic deformation with the measured shape error of ground workpiece, the cause for the shape error in case of grinding a long workpiece was investigated experimentally. From experimental results, it is confirmed that the main factor of the shape error of the long workpiece is its elastic deformation during grinding process.

Abstract: In cylindrical grinding, a sizing device is generally used to obtain the required dimension. However, the dimensional error can be caused by the thermal deformation of the workpiece even if grinding machine is controlled with the sizing device. To solve this problem, it is necessary to develop the grinding system that can consider the thermal deformation of the workpiece during grinding process. In this study, an advanced grinding system was developed, which can predict the net stock removal of ground workpiece immediately. The grinding experiment is carried out to verify the developed system.

Abstract: During the last decades, heat generation in grinding is one of the top concerns because high temperature under fabrication leads to less dimensional accuracy of a workpiece. Several studies with regard to grinding heat have been carried out, focused on micro phenomena of abrasive grains or macro phenomena of thermal deformation in grinding machines. However, these researches have been extensive, schematized information such as thermal deformation, and grinding temperature is indispensable for practical applications. In this study, we combined the simulation model of the plunge grinding process and the numerical analysis method with the differencing technique for the non-steady heat conduction problem, and have constructed the simulation technique for analyzing the heat problem in the workpiece. The simulation results provided information of the heat conduction, and the thermal deformation of the workpiece.