[in Japanese]

View full abstract

Outputs of grinding operations are usually estimated through experiences because of its difficulty to forecast the process. It is well known that the process is much affected by a lot of parameters of grinding condition, workpiece and wheel characteristics, including randomly distributed grains on wheel periphery. The present paper has tried to develop a reliable and practical simulation of the grinding process. Namely, the method is based on replacing an actual grinding process to a computer program as faithfully as possible, where working mode of effective grains, their cutting mechanism, effect of machine rigidity, etc. are taken into account.

View full abstract

Straight or circular cutting edges at the chisel edge portion of conventional twist drills are formed usingelectrical discharge machining. Various shapes of main cutting edge changing into a concave or edge from a straight one are obtained by grinding the flank surface of the conventional twist drill for different pointangles. Cutting edge configurations of these drills are analyzed geometrically, and expresslons for inclination angleand normal rake angle along the cutting edge are derived. From the geometrical analysis, it is found that theinclination angle at the chisel edge portion takes positive or negative values with the location of straight or circularcutting edges and the normal rake angle along the main cutting edge of the drill having a32°helix angle varies onlyabout 20° by changing the point angle largely from 90° to 150°The torque and thrust force of these drills aremeasured using a piezo-electric type dynamometer, and the relations between chip form and cutting forces are discussed.

View full abstract

In the previous papers, the chipping and wear of the tip of grain in single-grit microcutting test of steels were studied for superabrasive grains. In this study, the cutting forces (F_n, F_t) have been measured in the same microcutting test, where the maximum depth of cut was 40 μm and cutting speed being 5.6 m/s. Three types of diamond grain (MSD, MBS 750, MBS 70 - # 12) and a CBN grain were used for the test. Also, conically shaped P 30 carbide was used at the test for the discussion of the effect of grain shape. Thus, the effects of depth of cut, grain type, and grain shape on the cutting forces were studied. It was evident that the effect of shape (specially rake angle) on the forces was very significant, but there was no substantial difference in the forces between diamond grain types.

View full abstract

A temperature at the tip of a conical cutting tool is measured immediately after micro chip forming using an infrared radiation pyrometer with an optical fiber. The fundamental structure of this pyrometer is that the infrared flux radiated from the tip of the conical cutting tool after cutting is accepted and transmitted to an infrared detector InSb by an optical fiber. The measurement accurancy when applying the pyrometer to the experiment is investigated theoretically. The temperature at the tip of the conical tool at various cooling times after cutting is measured using this pyrometer. A carbon steel and a tungsten are used as workpieces. A cooling characteristic of the tool is analyzed by heat transfer theory. Applying the theoretical results to the experimental results, the temperature of the tip of the conical tool just after cutting is estimated to be 1500°C for carbon steel and 2400°C for tungsten; 1500°C is almost equal to the melting point of carbon steel.

View full abstract

In Electrical Discharge Machining(EDM), the residual stress generates on the surface of the workpiece because of repetitive heating and cooling process. The stress causes decrease of fatigue strength, delayed fracture and stress corrosion which affect quality of the workpiece. In the previous papers, the distributions of temperature and thermal stress in impulsive EDM has been analyzed by means of Finite Element Method taking into consideration the temperature dependency of mechanical properties and thermal physical properties of workpiece material. In this paper, the procedure for analysis of the region in which the crack must be generated is developed and time variation of the region is investigated under various machining conditions. The result shows that, on the machined surface, it is possible to generate cracks along radial and circumferential directions, because the residual stress exceeds the tensile strength.

View full abstract

Quantum size effects of amorphous silicon/amorphous silicon carbide (a-Si(:H)/a-SiC(:H)) multilayer films prepared by a dual rf magnetron sputtering method are investigated by measurements of Vacuum Ultraviolet Photoelectron Spectroscopy (UPS) and optical absorption. Valence band offsets of a-Si/a-SiC and a-Si:H/a-SiC:H heterojunctions are 0.3 and 0.05 eV, respectively. Optical gaps of a-Si, a-SiC, a-Si:H and a-SiC:H are 1.22, 1.52, 1.87 and 2.20 eV, respectively. In a-Si:H/aSiC:H multilayer film the quantum well layer thickness dependence of the optical gap is found to be in good agreement with a 1-dimensional quantum well model. It is obtained that the effective mass of electron in a-Si:H film is 0.15 m_o (m_o; the mass of free electron). In a-Si/a-SiC multilayer film quantum size effect does not appear. It can be considered that the effective mass of hole in a-Si film is more than hundred times as large as that of free electron.

View full abstract

A three-dimensional laser profile processing system with focusing control of linear shaped beam of uniform power density has been developed. In the system, YAG laser beam is focused through a shaping mask, cylindrical lens and convex lens so that the power density is uniform on the target material. Experimental relationships between the defocusing distance and processed depth are obtained. The system is operated due to the data of the model profile obtained by an optical position sensor. It was applied to generate a profile of saw blade in Si₃N₄ ceramics. Although the accuracy of generated profile is not high, it can be made higher by the improvement in sensing system of the model and controlling speed of the lens system in the direction of z-axis.

View full abstract

In order to analyse material surface processing, first-principles molecular-dynamics simulations are carried out. Density-functional theory, norm-conserving pseudopotential and plane-wave basis are used. Atomic, bond populations and local energy are proposed as estimation parameters of the stability of material surface atoms. As an example of application, H-termination process of Si (001) surface atom is numerically analysed. The results are the followings: The backbond strength of F-terminated Si surface atom decreases, and the Si atom shifts upward from the surface. When HF molecule attacks to the weakened Si backbond, the backbond vanishes and the H atom of HF moves to the Si atom of the second layer. From these results, it is confirmed that proposed method is useful to analyse surface chemical processes.

View full abstract

This paper describes development of the CAD/CAM system based on the "skewed cube modeler" named DIMOS. To handle complicated 3-D die shapes with CAD/CAM systems, it is necessary to develop the new modeling method suitable for 3-D die shapes. The DIMOS method, based on the decomposition method, is represented by "shell", "seed" and "split point", and has advanced capabilities to treat both sculptured surfaces and solid model at the same time. The CAD/CAM system using the die manufacturing model based on DIMOS method generate tool path from 3-D die shapes with high accuracy and computing speed.

View full abstract

Grinding wheel elasticity has been assessed in terms of the spring constant of the grain mounting. Few knowledge are, however, given on the spring constant of diamond wheel. In this paper, the micro compression test of the individual grains on diamond cluster and grinding of ceramics with diamond wheel are carried out to evaluate the spring constants in these stages. The main results are as follows: (1) The force P - deflection δ curve of the compressed grain on the cluster is characterized by the gradual increase in ΔP/Δδ, the constant ΔP/Δδ, and the gradual decrease in ΔP/Δδ, in turns with increase in P. (2) The spring constant of grain mounting obtained from the constant inclination, ΔP/Δδ is proportional to the average grain diameter (ΔP/Δδ =k·d): k=12.5mN/μm₂ (resinoid bonded wheel) and 37.5mN/ μm₂ (metal bonded wheel). (3) The estimated spring constant during the grinding whose condition is not heavy is the same as that from the compression test.

View full abstract

To avoid collisions of two objects such as a workpiece and a tool, computation of collision domain in which the tip of the tool cannot locate is crucial. Collision domain can well be computed by Inverted Template Method using envelope operation. In this paper, a high-speed algorithm is proposed for three dimensional envelope operation by means of convolution operation. From two input domains α and β, an envelope domain γ is quickly computed by three dimensional Fast Fourier Transform (3D-FFT). Because it needs a huge memory capacity to convolute a whole cubic space precisely at one time, octree model is adopted to represent each of whole domains α, β and γ and Double-stage FFT method is established. First, the upper parts of input octree α and β are convoluted to get the rough sketch of the envelope domain γ. Second, pairs of lower subcubes of α and β are convoluted to compute precise 3D bitmaps. Among all the pairs, only the corresponding to boundary leaf cells of the upper γ octree are extracted. Each set of bitmaps for a leaf cell is converted into a suboctree through OR operation and added under the upper tree. Comparison of computing time with a precedent algorithm shows the superiority of Double-stage FFT method.

View full abstract

In this paper, knowledge and its utilization in design processes are analyzed in two ways by using protocol data. First, we extract 134 pieces of knowledge that are directly appeared in the protocol data. We classify them into nine categories and discuss how they are used in design processes. Second, we assume that knowledge is represented by relationship of concepts, and extract concepts and relations of concepts from the protocol data. We interpret the extracted network of concepts by the connectionist approach. We identify the important concepts and how their degrees of importance change during the design process by regarding the activations of nodes as the intensity of importance.

View full abstract

Application of bang-bang control to reduce the servo error generated by nonlinear elements in numerically controlled machine tools is presented in this paper. It has been prooved that the modified inverse transfer function control can eliminate the servo error of numerically controlled machine tools with linear elements but not the servo error with linear elements. The latter servo error can be reduced by the bang-bang control of compensating current for driving motor at start and direction change of the motion. As a result, by providing the machining centers with the control system, the geometrical accuracy of the workpiece at the quadrant corner is reduced from 27μm to 14μm and that at steep and gentle slope cutting is reduced from 27 μm to 7μm when cutting die weighing 98kN at the feed rate 10m/min.

View full abstract

We describe the profile measurement of a rough surface using Abramson interferometry. This interferometer is classified into an oblique incident interferometer with a right-angled prism close to a sample. For the automatic analysis of phase distribution of interference fringe, the phase shifting technique is applied. The reference phase is shifted by changing the refractive index between the prism and the sample. This system can measure the flatness of a rough surface and/or a steep uneven surface, with several ten micro-meters order, that can not be measured by conventional interferometers. The surface profile of a ceramic plate is measured to prove our method.

View full abstract

Human body dynamography(HBD) is proposed as a convenient system for analyzing and evaluating human body motions specifically the torque acting at joints of a human body. Torque intensity is visually displayed using a color scale. A kinetic model of the human body, consisting of fifteen rigid cylinders equivalent to the body segments and the equations of motion, is derived to estimate each torque during joint action. A sequence of motions in both the frontal and sagittal planes is simultaneously taken by two video cameras, and the coordinates of individual joints are digitized with a PC. Visualization of torque was tested on the planar motions in a popular physical exercise of a Japanese radio program. Rings centered on individual joints were drawn on a skeletal model, and colored corresponding to the magnitude of torque. Torque was normalized by the cross·section area (Normalization 1) and volume (Normalization 2) of each segment. Additionally, HBD was compared with thermography to evaluate the normalizations.

View full abstract

It is well known method to measure the precision profile with three or more displacement sensors. In case of multi point method using Fourier transform, the changes of the measuring interval can be done easily. Rut this measuring method was discussed separately between circle profile measurement and straight profile measurement. In this study, the above methods are expressed by the consolidated forms using transfer function. Therefore the performance index on error propagation has been derivated from the transfer function too. The characteristic of the transfer function is revealed to be availability analytically.

View full abstract

The purpose of the study is to develop an optical non-contact displacement sensor which has the following characteristics; (1) direct measurement of any surfaces, (2) high accuracy, (3) large measurement range, and (4) high follow-up speed. In the previous papers, an optical fiber herterodyne interferometry sensor was introduced and accuracy, measurement range and follow-up speed were reported. However, the following problems were left unsolved: (1) the follow-up speed changed periodically with the distance, (2) the follow-up speed was not high enough, and (3) the displacement could not be measured when the target was a mirror, In this paper, first, an optical isolator is used to cut off light returning to the laser diode. The periodical change of the follow-up speed is removed, which enlarges the measurement range from 26mm to more than 40mm. The displacement of a mirror target can also be measured. Then, a triangular modulation method is introduced to heighten the follow-up speed. The maxmium follow-up speed obtained is 15.4mm/s, which is 2.3 times of the sawtooth modulation method.

View full abstract

A laser diode (λ = 780 nm) probe, from which an half-circular beam irradiates in-focus to an objective surface and the diffraction pattern formed on the suface near the focal point is detected by a two-part-divided photo-diode throughout the same optical path, is proposed. The principle of the measurement is discussed by the diffraction pattern change analysis. The response characteristics of the probe prepared are measured; the obtained dynamic ranges are ±1 μm-2 nm for f=3.6 mm, and ±100-0.2 μm forf =23 mm lens. When the output signal, the difference currents of the two parts of the detector, is normarized by the summation of them, it becomes a simple function of displacements inspite of the condition of the material surface; the displacement response curves for a mirror sample, a low reflectivity glass sample and a steel sample having a mean roughness of 1.3 μm, are quite similar.

View full abstract