The system for manufacturing dental crown has been developed by applying CAD/CAM technology, to attain stable and sufficient supply of prosthetic teeth, which will be serious social requirement in the 21st century. This report describes CAM system consisting of CAM software that tool path can be made automatically and 5-axis control NC machining center. Standard procedure with single supporting work is also proposed, and this procedure about 60 minutes processing time is realized.

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This paper describes the method of reconstructing a polyhedron system with the function of checking mistakes. This function is aimed to find and check mistakes on the three orthographic views, and to inform the mistakes to a user. At the same time, this mistake-checking function has been united to the polyhedron reconstruction system. As a result, we can use this system efficiently. Finally the effectiveness of the mistake-checking mechanism has been comfirmed with respect to many types of polyhedra.

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This paper describes a grating projection method for three-dimensional profile measurement of specular objects and the method is utilized to measure a concave-shaped mirror that is difficult to measure using conventional non-contact methods in short time. A "deformed grating pattern" is observed when the reference grating is projected onto a mirror-like surface. This pattern formed by the surface reflection is captured by a CCD camera and analyzed on the basis of phase shifting technique to give three-dimensional profile of the specimen. Experimental results are shown with respect to an ellipsoidal mirror to verify the principle proposed here.

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In the assembly robot system, CCD camera is useed to measure the distance to the object. The camera is mainly used as the single camera system. But recently practical 3D measuring system is demanded for assembly robot system to utilize its positioning and repeat accuracy with the support of the 3D measuring ability. In this paper stereo camera system is studied. A camera model is introduced to calculate the 3D coordinates of the object point in the world coordinate system, and a new geometrical calibration method of the stereo camera system is presented. By the experimental results using f16mm and F1.6 lenses about 0.5 mm accuracy in 5mm cubic is gained. The result is not sufficient for assembly robot, but the prospect to improve, it to 0.01mm accuracy has been discussed.

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A new technique which can measure speckle phase with high accuracy is proposed. The technique continuously captures about 100 images under slow phase-shifting and then calculates phase data about each captured image. The calculated phase data are averaged along the capturing order to suppress the noise components due to air fluctuation and vibration of circumstance. Only the average, without other filtering, is not enough to suppress noise which are caused by low modulation data in specklegrams. Therefore, the average is combined with the data replacing which replaces low modulation data with high modulation data around them. The well-known median filter is also combined. With the combined method the fluctuation of phase data is extremely improved. Utility of the combined method is demonstrated through a practical deformation measurement

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Different types of power add-on units for attendant propelled wheelchairs have been developed and some of them are available on the market. Most of them do not consider the operator's pushing or pulling capability and he must adjust the power with a switch while holding the pushing handle. It is not easy for elderly people to do so especially when they need to take a prompt action such as sudden stop. Sensing the propulsion force would make the operation much easier instead of operating the switch. In this study, one motor system is adopted with a differential gear for maneuverability and compactness. As propulsion force sensor, a magnetostrictive sensor is employed and it detects pushing or pulling force by the operator. As control method a model reference control is proposed. The power assist is controlled as if a lightweight wheelchair was operated on solid flat ground by the operator. The model is described with mass and viscous damping factor. A prototype was made and initially tested on floor and slope. It was found effective to reduce operator's propelling force. This paper describes its control method, mechanical design, control circuit, control simulation and test results of the prototype.

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This study deals with the technology of high speed end milling of hardened steel by a high speed milling machine with an air spindle. Nowadays, for machining of dies and molds high speed end milling method has been developed to improve machining efficiency. In the previous paper, it was shown that use of a high speed machine enables stable machining to be carried out. But, still some problems to be solved for high efficient end milling of metal molds and dies, which have deep cavities. In this paper, stability of high speed end milling of hardened steel in case of long overhang are discussed. The main results are as follows ; (1) The stable range of high speed end milling in case of long overhang becomes narrower than that under standard conditions. (2) The proposed easy testing method of stability discrimination is effective for selecting stable cutting conditions in case of long overhang. (3) Both high efficiency and accurate surface without need of polishing were realized as a result of applying our method to high speed end milling of the crankshaft forging die.

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A rapid prototyping is reported on direct fabrication from powder material using a laser. This process is based on laminated object manufacturing (LOM) composing of three stages: supplying of powder, shaping of a laminate and superposing of laminates. For the solidification of powder a high power laser beam is irradiated. Such a problem, however, is caused that most of the molten material splashes away at the moment of laser beam irradiation. To solve this problem, the supplied powder is compressed prior to laser projection, and a laser is irradiated with two steps. First, the compressed powder is solidified to the lamina with low output power and then, the lamina is combined with the solid with higher output power. In the case of pure iron powder, for instance, the powder is compressed to be 60% in volume by the pressure of 117MPa, and a concave laminate with the thickness of 0.5 mm and a large curvature is formed when the beam is projected onto the compressed surface from a laser with 5.4J output power. The lamina is combined with the solid without much splashing if the beam is projected once again on the surface (12J). The solid object thus fabricated has tensile strength exceeding 300MPa and various shapes of laminated objects can be realized.

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The process of the diamond turning of (111) single-crystal copper was studied using molecular dynamics (MD) simulation. Even under sub-nanometric depth of cut conditions, activated slip systems can be determined by the Schmid factor, which is calculated from a given macroscopic cutting-force direction. This result suggests that slip deformation behavior in diamond-turned single-crystal silicon under a submicrometric depth of cut may be examined by MD simulation in the turning process of copper. This is because both materials have exactly the same {111} <110> slip system, and, furthermore, silicon can be deformed plastically through turning by activating only a few specific slip systems. The turning process of silicon based on the MD analyses was evaluated. The material removal process changed according to the kind of slip system activated, and this depended on the cutting conditions, such as shape cutting tool and depth of cut. MD analysis indicated that slip deformation on the (111) plane in parallel to the turned surface played an important role in realizing ductile-regime turning.

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This paper deals with the basic research on super-smooth polishing method and surface irregularities of polisher affecting polishing characteristics. Firstly, a polishing model was proposed taking account of the contacting conditions between work and polisher, the measuring conditions of the surface irregularities on polyurethane polisher were examined by using a stylus type 3-dimensional surface roughness measuring instrument. Then, the correlation between polishing results for glass works and the polisher irregularities was discussed. (1) In measuring the surface irregularities of polishers, it was found that 500μm in radius at form stylus tip was suitable. (2) The polisher irregularities showed maximum just after dressing, and decreased little by little as polishing advanced. The values were not recovered remarkably by washing with using a plastic brush. (3) Although the values of irregularities at porous polishers were independent of the dressing pressure, a rather hard polisher having the foam structure showed a noteworthy result that the smaller values in polisher irregularities were given when the higher pressure applied. (4) The specific stock removal amount, when using the porous polishers, showed a tendency to be small after just dressing, to increase as polishing advancing, and to decrease after brush washing. While, when using the hard polisher gave a completely reverse result. (5) In the case of polishing surface composed of various materials, the step height difference between the material were arranged as follows: (after enough polishing) < (after brush washing) < (after just dressing). Such tendency has good agreement with an order of polisher surface irregularities.

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New guideway for linear motion is desired for lithography equipments to realize new progress in semiconductor manufacturing. Water-hydrostatic bearing is the best choice for such equipments in clean room, which provides high stiffness and damping, while producing no contamination. The conventional design rule of theoretical or experimental for hydrostatic bearing has been proved to be of no use for water and the new design method has been proposed in our former paper. In this study, the new test stage, which has one linear axis and is equipped with counter type water-hydrostatic bearings, has been manufactured by applying the above design method, and investigated in point of bearing and positioning element. As a result, measured recess pressure, bearing stiffness and flow volume have coincided approximately with simulation values and also have cleared the required specifications. Thus the design method has been verified to be effective in practical use by experiment. By employing steel belt drive system and a conventional NC controller, the positioning repeatability and resolution were evaluated to be within lower sub-micron level. This study can point out the possibility of new type stage which can be available in clean room.

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This paper describes a method of controlling the pattern width for laser beam writing. Line width control is one of the fastest and most efficient ways modulating the laser beam for making photo mask patterns. A small change in the beam "waist" (defocusing) can result in a big change in the line width. First, a theoretical analysis is made, suggesting that line width is controllable over a wide range by using the defocusing method. Secondly, experimental equipment and procedures are described. By using a large numerical aperture lens and a focusing actuator to defocus the laser beam continuously, the beam waist pattern is exposed to the photo resist. Lastly, experimental results. are compared with the theoretical predictions. Taking into account the sensitivity of the photo resist to the Gaussian beam laser, a good correlation is shown to exist between the experimental results and theoretical analysis. Further discussion concludes that constant power density writing offers a wider control range of line width than constant power writing.

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Hirofumi SUZUKI, Toshiro HIGUCHI, Naoshi WAHMA, Takayuki KITAJIMA, Shigeki OKUYAMA and Hiroshi YAMAZAKI This paper deals with the precision grinding of micro fresnel shape with some micro grooves. Fresnel lenses are useful for the next generation type of optical devices because of its thin structure and excellent optical characteristics. In the conventional machining method, the lens materials were restricted to plastics, because the cutting tool was a single crystal diamond and the molding die material was restricted to a soft metal such as copper or electroless deposited nickel-phosphorous (Ni-P) alloy. In this paper, a grinding system of 4-axes (X, Y, Z, C), and a new grinding method with vertically controlled grinding spindle and the disk type wheel of knife edged shape were developed. At first, the effects of the wheel feed rate control method on the workpiece form accuracies and surface roughness of flat shape WC workpiece were discussed. Finally, in a feasibility study of the fresnel shape grinding, the molding dies of tungsten carbide for glass lens were ground in trial. The experimental results show that a form accuracy of about 0.1 U mP V and surface roughness of about 10 nmRy were obtained and this new grinding system was useful.

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Penetration mechanisms of welding by continuous wave (CW) YAG laser beam for mild steel were discussed. Bead-on-plate tests were carried out varing laser beam power and welding speed, and the cross-sectional shapes of the welds were measured. The fundamental welding characteristics for mild steel by YAG laser beam were estimated in comparison with those by CO₂ laser beam. The results obtaine are as follows. (1) The penetration mechanism of key-hole welding in a steady state by YAG laser beam agrees with the heat conduction theory for a wedge type volume heat source model, like that by CO₂ laser beam. (2) YAG laser beam has lower threshold power to enter fusion of mild steel and its absorption efficiency is less dependent upon the cavity depth of molten pool than CO₂ laser beam. Then, input power can be controlled to adjust the irradiating beam power, that is necessary to slow down penetration depth at the end of weld.

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The elastic modulus of the grinding stone part in super abrasive grinding wheels is considered to be an important mechanical property to estimate the grinding performance of the wheels, to select the suitable grinding wheel case by case. This paper describes the approximate formula of elastic modulus on the matrix type grinding stone without pore. This formula is obtained from the acoustic model based on the propagation of the elastic wave. The elastic modulus of the grinding stone can be conveniently calculated by the formula, if the mechanical property of grain and bond, and the composition of the grinding stone have been known. The elastic modulus measured by bending test and ultrasonic pulse method are compared with the calculated results in order to evaluate the accuracy of the formula. As a result of the comparison, it is confirmed that both of the measured elastic modulus of the grinding stone coincide with the calculated results, and there are the suitability of the formula and the acoustic model.

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The aim of this paper is to clarify experimentally the stability of regenerative chatter vibration in ball end milling. The validity of the proposed theory is also examined by systematic experiments. The results obtained are as follows. (1) It is seen from the cutting forces and photographs of machined surfaces that the chatter vibration occurs easily in the region where the instantaneous depth of cut is small. (2) The chatter stability in "downward cross-feed, up milling" is highest in comparison with other cutting modes. (3) In the case of "upward cross-feed, up milling", depth of cut hardly effects on the chatter stability, while large cross-feed heightens the chatter stability. (4) High inclination angle of workpiece results in low stability. (5) The chatter stability limits measured in experiments are in good agreement with the limits predicted in the theoretical analysis.

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Fully continuous hot finishing line, so called "Endless hot strip rolling process", has started in operation for the first time in the world at our works. In this process, sheet bars are joined at the entry side of the hot finishing mill and then rolled continuously. If a joint with a raised area is rolled, an overlap defect will occur in the initial stage of rolling. To prevent this problem, a method of removing the raised portion on joined sheet bars simultaneously using milling was developed This paper describes the main technologies which were developed in realizing the milling of high temperature steel surface over 900 °C. The following experimental results which used saw type cutter made by S55C are confirmed (1) Forming of chip adhesion on the cutting edge depend on the milling speed, and good milling achieved under the speed over 80 m/s. (2) Under the milling condition mentioned above, wearing progress speed of cutting edge is extremely slow and the milling of 6500 cycles achieved under milling length of 300 mm/cycle. (3) Under this specification of milling speed, the production plant has installed in 1995 and it is operating satisfactorily without trouble.

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The Influence of the Torsional Vibration of Ballscrew on the Stability of NC Servo Drive System Jun FUJITA, Sadaji HAYAMA, Minoru HAMAMURA, Yoshiaki KAKINO, Atsushi MATSUBARA and Satoshi OHWAKI The influence of the torsional vibration of ballscrew on the stability of NC servo drive system has been studied in this paper. Theoretical analysis using mathematical model of the baliscrew drive system shows the possibility of the unstability of servo drive system due to the interacted effect of torsional vibration, the dead time and phase lag of the 1st order filter. Experimental analysis using the existing NC drive system shows fairly good coincidence with the calculated results.

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