Takanori Fujiwara

Cutting mechanism of fine ceramics with a single point diamond

Abstract Circular cutting with a single point diamond cutting edge, in which the depth of cut is very small but reaches a maximum at one point, has been carried out in order to investigate the cutting of sialon and/or partially stabilized zirconia under conditions similar to grinding. This has been carried out by investigating the sliding phenomenon of a diamond cutting edge, the normal cutting force, groove profile, stock removal and so on. It has become clear that there are three different regions within the cut: elastic, plastic and cutting regions are all present when there is interference between a diamond grain and a fine ceramic. A cutting groove is generated by plastic deformation as well as brittle fracture.

Analysis of the grinding mechanism with wheel head oscillating type CNC crankshaft pin grinder

In this study, the crankshaft pin grinding mechanism, which is carried out with wheel head oscillating type CNC crankshaft pin grinder, is theoretically analyzed. In order to maintain grinding process, the pin rotates and also rocks along wheel working surface, because the wheel head oscillates with journal rotation. Then, it is made clear that cylindrical plunge grinding process progresses in the pin grinding process for the first time. Therefore, grinding speed ratio, which is defined as ratio of substantial pin surface speed to wheel surface speed, is firstly formulated. Secondly, undeformed chip size generated by a grain is estimated with the grinding velocity ratio. Finally, the grinding performance is predicted with experimental equations, which obtained previous study. By this simulation, it is made clear that dimensional accuracy and also surface roughness vary on whole of the pin surface with constant journal rotation grinding method. On the contrary, deviations of both the dimensional accuracy and the surface roughness are reduced with controlled speed ratio grinding method, in which journal rotation speed is adequately controlled.

Visual Simulation of Grinding Process

Publisher Summary Grinding is one of the machining methods for finishing that is performed by using a large number of abrasive grains with irregular shapes and random distribution. While this feature enables accurate and high quality machining, it complicates analysis of the grinding process. In order to solve this problem, several computer simulations have been carried out using the Monte Carlo Method. Most of them statically calculate geometric interference between a grain and a workpiece, and have not provided enough achievements for practical applications. This chapter outlines the development of a simulation program based on the elastic behavior model of a grain. The program focuses on the generation process of a workpiece surface, and simulates the interaction of grains with a workpiece, which includes the elastic and plastic deformation and the removal of workpiece material. The simulation result is visualized using a three-dimensional graphics technique. The chapter illustrates an example, which verifies that the simulation program makes it easy to analyze the microscopic grinding phenomena, and can be used as a practical tool for predicting the grinding results and for optimizing grinding parameters.

Analysis of the Cam Grinding Mechanism with a CNC Cam Grinder

The cam grinding mechanism with a CNC cam grinder is analyzed. A numerical simulation method has been developed to obtain the grinding results. Special cam grinding methods, which appropriately control both the rotational angle speed of workpiece and the horizontal travel speed of wheel head, are presented in order to achieve higher precision in cam grinding. It is found that suitable setting of both the rotational angular velocity of workpiece and the feed rate of wheel head provides stable grinding results. Introduction In the cam grinding process, both the curvature radius and the peripheral surface speed of workpiece continuously change with the rotation of workpiece. Then, in the grinding method with oscillatory camshaft grinder, it was made clear that the normal grinding force and the surface roughness become larger at the position with higher speed ratio in the previous study [1]. Furthermore, in the controlled speed ratio grinding method, the grinding quality is improved by the adaptive control of rotational angle speed of workpiece. It is also ordinary to grind a cam with master-less type cam grinder, which wheel head moves horizontally controlled by CNC recently [2]. In this study, in order to establish a high precision in the cam grinding method, the cam grinding mechanism with CNC camshaft grinder is analyzed. Furthermore, the unique grinding methods, which control both the rotational angle speed of workpiece and the horizontal travel speed of the wheel head appropriately, such as the controlled normal force grinding method, the controlled surface roughness grinding method and the controlled speed ratio grinding method are presented, and the grinding results obtained by the methods are investigated with a numerical simulation. Analysis Method for the Cam Grinding Mechanism Fig. 1 shows an analysis model of the cam grinding mechanism with the CNC camshaft grinder. The grinding wheel, which radius is Rs and the center position is Os, rotates at peripheral speed Vs.

Study on High Precision Contour Grinding (2nd Report)

In contour grinding process with ball-end grinding wheel, successive cutting point spacing and also wheel peripheral speed change continuously on a working wheel surface. And these parameters will have an influence on grinding mechanism. Then, in order to make grinding mechanism clear, undeformed chip shape is theoretically analyzed in this paper. Fundamental relationships about substantial parameters, which represent the undeformed chip shape, such as chip thickness, chip length, interference angle and cross-sectional chip area, are theoretically analyzed. Then, in order to obtain these parameters, numerical simulation method is established. The undeformed chip shape is symmetrical form to rotational angle of cutting edge, and is extremely longer and also thinner than that in ordinary external cylindrical plunge grinding. Effects of tool and grinding conditions on the undeformed chip shape are investigated, and it made clear that an increase of wheel peripheral surface speed should be reduce cutting force affected on a grain. Furthermore, grinding force distribution on a wheel working surface is predicted considering with the chip thickness and the wheel peripheral speed.

Study on High Precision Contour Grinding. (1st Report). Effects of Curvature Radius Change of Workpiece and Thermal Deformation of Machine Structure.

In order to establish the high precision contour grinding method, the reference position correct sensor is first developed for compensating the thermal deformation of a machine structure, and then the controlled normal force grinding method is developed to control a fluctuation of a normal grinding force. Main conclusions obtained in this study are as follows: (1) It is made possible to correct the error of wheel depth of cut accurately, with using developed reference position correct sensor. (2) The controlled normal force grinding technique is developed, through the analysis of the feed rate setting conditions correspond to the curvature variation of a workpiece. (3) High performance contour grinding method, with which both constant surface roughness and high dimensional accuracy can be obtained in any curvature radius of a workpiece, is developed by using the controlled normal force grinding method incorporate the reference position correct sensor.

Development of a grinding force dynamometer based on wheel shaft deflection for a grinding center

本論文で得られた結論は以下のとおりである, (1) 研削抵抗による砥石軸の弾性変位量をうず電流式非接触変位計で検出する新しいインプロセス研削抵抗測定システムを開発し, 加工現場での研削抵抗監視に十分な性能を持つことが確認された.(2) 圧電式動力計は, 工作物の固定方法の影響で, 工作物と動力計流入する加工熱に起因する見掛けの力がノイズとして測定信号に重畳する.しかし, 砥石軸動力計の場合このような加工熱に起因する測定ノイズは本質的に混入しない.(3) 従来の研削理論では, 研削点における工作物の曲率半径すなわち半径が等しい区間を加工する際の研削抵抗は一定と考えられるが, 輪郭加工中は研削抵抗の大きさが異なる.このことは, 実質の砥石切込み量に対する工作物および/あるいは砥石の熱変形の影響を示唆していると考えられる.

A quantitative analysis of grinding process of partially stabilized zirconia.

In order to describe quantitatively the grinding process of partially stabilized zirconia (PSZ) with metal bonded diamond wheel, the analytical method established for metal grinding is applied to the grinding process of fine ceramics, and the theoretical values are compared to the experimental values. It is made clear that the plunge grinding process of PSZ with metal bonded diamond wheel can be represented by five independent characteristic parameters such as the size generation acceleration, the wheel wear rate, the grinding system stiffness, the contact stiffness and the cutting stiffness. By the characteristic parameters, variations of the grinding force, the stock removal, the residual stock through a grinding cycle and the grinding cycle time can be predicted.

Cylindrical plunge grinding process of sialon.

Cylindrical plunge grinding process and surface generation process of Sialon are experimentally investigated with bronze bond diamond wheel, analyzing grinding force, surface roughness, wheel wear, ground surface and so on. Main conclusions obtained in this study are as follows : (1) In a cylindrical plunge grinding process of Sialon with bronze bond diamond wheel, there are three distinct grinding processes such as spark-in, steady and spark-out. (2) Ground surface is formed by plastic deformation as well as brittle fracture in grinding Sialon. (3) Diamond grain primarily wears in attrition. (4) Grinding force increases with an increase of setting depth of cut, while surface roughness is hardly influenced by setting depth of cut.