Takazo Yamada

Application of Superfinishing to Curved Surfaces

It is well known that the superfinishing is a high efficient surface finishing method to cylindrical workpieces. In this method, grinding stones are pressed to the outside of cylindrical surfaces. Rotating cylindrical workpieces and making relative vibrations between grinding stones and ground surfaces in the directions of the center lines of workpiece rotations, the cylindrical surfaces are ground and mirror surfaces are realized relatively in short time. Therefore, this finishing method is widely applied to the finishing of precise machine elements. However, this method cannot be applied in case of that the workpiece which is not simple cylindrical geometries so far. In this study, a new application method of superfinishing to the cylindrical workpieces having curved parts is proposed and its performance is discussed experimentally.

Contact Stiffness of Grinding Wheels due to the Difference of Table Feed Rate

Usually, the contact stiffness between a grinding wheel and a workpiece has been measured in a stationary state. So, in this study, the contact stiffness under the grinding operation is measured under different table feed rate of the workpiece. From this result, it is known that, while the contact stiffness in the stationary state increases with the increase of the contact force, the contact stiffness under the grinding operation decreases with the increase of the normal grinding force relating the table feed rate. In this paper, since the number of contacting abrasive grain with workpiece is constant irrespective of the table feed rate, and the residual stock removal of workpiece is varied by the table feed rate, it is clarified that the contact stiffness under the grinding operation differs from the contact stiffness measured by the stationary state.

Generation of Microelectrodes for Micro EDM

A new turning method to control the thrust force to be zero has already been proposed in our laboratory, and it is shown that micro shafts which diameters are less than 1 mm can be generated stably and repeatedly by applying this turning method. As an application of this turning method, a generating method of electrodes of micro electric discharge machining, EDM, for micro holes is proposed. When drilling a micro hole by EDM using an electrode with high aspect ratio, machined chip is difficult to be exhausted. Therefore, machining time has a tendency to be long and the electrode consumption becomes large. Standing in such a viewpoint, a new method to exhaust the chip smoothly by forming the micro electrode geometry is proposed in this paper. As the results of this study, it is confirmed that the machining time of micro holes can be shorted and the consumption of electrode can also be decreased experimentally.

Effect of Machining of Small Tools by Means of Focused Ion Beam

Micro holes which diameters are more than 0.1 mm are mechanically machined.　However since the ideal sharp cutting edges are difficult to be made in micro drills, fine geometrical shape of micro holes is difficult to be obtained. In this study, the influence of the geometrical shape of cutting edge is experimentally discussed. In order to carry out experimental evaluation, focused ion beam is used to make the geometrical shapes of micro drills.

Estimation of the Grinding Time by Means of the Grinding Process Model

In grinding operation, elastic deformations of the grinding machine and the grinding wheel induce a residual stock removal of workpiece. On the other hand, thermal expansions of the workpiece and the grinding wheel increase the depth of cut. Therefore, calculation of a ground depth of cut and/or the grinding time has to be considered by the elastic deformations and the thermal expansions. From such a viewpoint, in this study, grinding process model taking into account the elastic deformations and the thermal expansions was proposed. This paper aims to estimate the grinding time by means of the proposed grinding process model.

Calculation of Effective Ground Depth of Cut by Means of Grinding Process Model

In order to obtain the effective depth of cut on the ground surface, a new grinding process model taking into account thermal expansions of the grinding wheel and the workpiece, elastic deformations of the grinding machine, the grinding wheel and the workpiece and the wheel wear was proposed. Using proposed model, the effective depth of cut was calculated using measured results of the applied depth of cut and the normal grinding force.

Experimental Evaluation of Grinding Mechanism in Micro Depth of Cut

In order to make clear the grinding mechanism in micro depth of cut, micro grinding test with a diamond indenter having defined geometrical shape is carried out. As the experimental results, it is clarified that the ratio of two force components and the swell-out residual ratio in micro grinding have different tendencies from ordinary grinding area. Based on these results, it can be estimated that the grinding mechanism in micro grinding differs from the ordinary grinding mechanism.

Calculation of the Contact Stiffness of Grinding Wheel

It is considered that the contact stiffness between the grinding wheel and the workpiece depends on the number of the abrasive grains in contact with the workpiece and the support stiffness of a single abrasive grain. In this paper, the calculating method of the theoritical contact stiffness of grinding wheel in grinding operation was proposed. Comparing calculated results of the contact stiffness in grinding operation with measured it in the stationary state, the contact stiffness of the grinding wheel in grinding operation was investigated.

On Geometrical Errors and their Suppression in Turning Operation by Controlling Thrust Forces

In the case of turning workpieces having high aspect ratios, i.e. length divided by diameter, it is not so easy to obtain high cylindricity because of the elastic deformations due to the thrust forces taking place under operations. In this paper, the generating mechanism of geometrical errors is discussed and its suppressing method is proposed. That is, applying previously established controlling method of thrust forces to turning cylinders with high aspect ratios, it is confirmed that geometrical errors of workpieces due to the action of thrust forces can be suppressed.

Observation of Grinding Wheel Wear Patterns by Means of a 3-Dimensional Digital Measuring Method

Surface geometries of grinding wheels vary due to the wear in grinding process. Since the wheel wear patterns are affected by the grinding process, measuring and investigating these patterns quantitatively, grinding process can be evaluated whether appropriate or not. Utilizing a three-dimensional measuring device for wheel surfaces developed so far, this study aims to evaluate wheel wear patterns quantitatively. As the results, applying developed device, it is clarified that wheel wear pattern can be classified and evaluated quantitatively.