This paper describes the automatic calibration system for rotary encoders which is installed at the NRLM (National Research Laboratory of Metrology). The system consists of two rotary encoders, the precise rotating mechanism, the division mechanism, the error measurement circuit and the computer. The detecting methods of the slight angular differences are the time-conversion method and the counter method. Their resolutions are 0.002" at 5 rpm and 0.072" respectively. The two encoders are calibrated by the self-checking method so called the Equal-Division-Averaged Method without any reference encoder. By the preliminary examination, the all graduations of the two encoders can be calibrated and it is verified that their accuracy is approximately ±0.5" and its repeatability is ±0.02".
This paper proposes a method to measure surface profiles of flat glasses by using a shadow image generated by the surface corrugations. When a point light is projected to a screen through the glasses, surface corrugations work as lenses to modulate contrast on the screen. Peaks on the glass surface give brighter regions and valleys gives darker regions, so brightness profiles on the screen agree to surface profiles. Contrasts of shadow images are predicted by an optical theory and lens model of surface profiles. The predictions agree to experiments for various optical positioning and installation angle. High contrast profiles of shadow images do not always give high similarity to the surface profiles because of the blur for too strong lens effect and resolution limit. On an allowable condition, three samples are measured whose surface profiles have peak-to-valley corrugation of 10-65 nm. For each sample, both surface profiles and brightness profiles give similar waveforms. An error of 5 nm is defined from the difference between both profiles for a pitch of 1 mm. This simple method can be applied to measure the surface profiles of flat glass with high accuracy.
In our previous work, robust control structure based on disturbance observer for a fast and precise fine motion mechanism has been proposed. The functionality of the controller was verified using one axis of precise X-Y table combined with-one axis fine motion mechanism. As a further step in this paper, the approach is extended to two-axes fine motion mechanism with a SCARA robot as a real system to realize the final purpose, that is, the development of high-precision mounting robot. First, the paper introduces a high performance robot system based on a SCARA robot coupled with a fine motion mechanism which was developed in our laboratory. Second, the paper presents a control scheme that enables correction of possible offsets of the end-effector relative to the target and compensation of the oscillations at the end-point. Finally, experimental results show significant improvements in end-point accuracy and settling time achieved by the novel configuration of the coarse/fine robotic system. As a result, a repeatability (3σ) less than 2 μm and the CP positioning error (3σ) less than 4.0 μm were achieved by the coarse/fine robotic system.
To amplify dye laser intensity, injection locking of a 0.5W broad area laser (BAL) diode at 670.9nm was studied. The threshold current of BAL was dropped by the injection locking. Almost 90% of the total output power was able to be put in a single transverse mode. The spectral profile of injected BAL was almost the same as that of the master dye laser. The linewidth was determined to be less than 400kHz by beat-note spectrum between the master dye laser and the slave BAL. At the maximum gain of 20, the maximum output of 105mW was obtained for an injected power of 5mW and an injected current of 700mA. The locking bandwidths were 17GHz for gain 10 and 13GHz for gain 20. Compared with the conventional method to increase the dye laser intensity, where the pumping Ar+ laser power is increased, this method is quite effective with the lower energy consumption (<1/3800), with the lower cost (<1/4) and with the higher output power (>×2).
This paper presents the gravity compensation and kinematic calibration considering gravity for parallel mecha-nisms, which reduce position errors caused by elastic deformations of machine parts due to gravity. The influence on the elastic deformations to the positioning accuracy is analyzed using the model of force balance between gravity and the motor power. Then the inverse kinematics solution with gravity compensation is proposed, in which the kinematic parameters are updated gradually according to the traveling plate pose. This provides us a real time motion control with compensation not requiring extra compensation values. The kinematic calibration considering gravity is also proposed to identify kinamatic parameters with no load. In order to improve the positioning accuracy, the identified parameters are used with gravity compensation. These methods are applied on the parallel mechanism based milling machine, named HexaM, and the validity is verified by simulations and experiments.
This paper presents a new method for precision measurement of axial and angular motion errors in the main rotational axis of a manufacturing machine. Three displacement sensors and one angle sensor are used in this method. Applying a calculation technique, it is possible to separate axial motion error, two angular motion errors, and the circumference profile. The principle of this method is examined from the viewpoint of spatial frequency analysis. From this principle, it appears that this new method can measure all spatial frequencies, without omitting any frequency. A measurement system performed experiments. The measurement experiments confirmed the separate measurement of the profile and motion errors.
The present paper presents a new method to realize ultraprecision high-speed positioning by switching two feed drive methods, which are 'walking drive' proposed by the authors in the previous report and 'running drive' utilizing elliptical vibration. It is clarified that the walking drive is suitable for ultraprecision positioning and smooth and slow motion over long stroke but not advantageous for high speed motion. The walking drive positioner can also be driven at high speed by the running drive without changing any hardware. A new dual-mode feed drive system is developed in order to increase the maximum feed velocity by applying the running drive far from the desired position and switching to the walking drive near the desired position. It is confirmed experimentally that ultraprecision high-speed positioning with a settling time of about 400 ms for a step positioning of 10 mm and an allowable error of 5 nm is achieved by employing the dual-mode positioning system.
The condition of a grinding wheel surface has a strong influence on the grinding results, such as grinding force, temperature, and work-piece surface roughness. The automatic image processing system has been developed in order to examine a grinding wheel surface condition quickly and precisely. The system consists of three components; (a) the surface grinder equipped with a wheel spindle driven by the servo-motor positioned at the angle accuracy of 0.01 degrees, (b) the observation system of a grinding wheel surface with a micro-scope, a CCD camera and a video-capture-board using digital handling technique of microscopic images, and (c) the newly developed software program for the automatic extraction of cutting edges on the images. The components are controlled with a personal computer operated by a multi-task Windows-OS. The system can evaluate the cutting edge density, the successive cutting edge spacing and the cutting edge ratio by processing 900 images of a 200-mm-diameter wheel periphery by every 670-μm width at the accuracy of 19 μm within 120 minutes.
This paper describes a validation of the detection system with patterned illumination for convexo-concave defects on optical films by using the ray tracing method. The method is based on a phenomenon that stripe patterns in a reflected image are locally blurred by the existences of their defects. The high-contrast repetition pattern such as stripe is effective. The detection algorithm proposed in the previous report is shown briefly. Then, the ray tracing method is applied to the estimation of images reflected from the films. The estimated images are very much in accord with the experimental ones. By estimating in various conditions including defect size and optical arrangement, optimum pattern spacing is found.
The objective lens for DVD optical-heads must have high optical performance, being aligned in high accuracy on the optical head For high speed of this alignment process, a method based on wave aberration included in exit light from the objective lens on the optical head has been studied. An optical system based on stable shearing interference with diffraction grating has been devised, as well as algorithm that can detect coma aberration from fringe patterns formed in this optical system. This algorithm processes divisional area of patterns therefore this algorithm can detect coma at high speed, besides independently of spherical aberration or astigmatism Alignment system of the objective lens on DVD optical head based on these optical system and algorithm has been developed. This system detects coma at 0.5s intervals and repeatability of tilt measurement is 0.01°. This alignment system has achieved high-accuracy alignment of 0.14° at 3 σ that is enough for DVD optical-heads, attaining 1/3 to 1/4 alignment time of conventional jitter method or spot method.
This paper describes a vibration control system and a recognition of cutting state in sawing by a circular saw blade. In the machining using a dcircular saw blade, unstable vibration in the rotating shaft direction of the tool is generated by the effect of cutting edge angle or rake angle of the tool. This vibration causes generation of the noise and the tool failure, and the productivity remarkably lowers. In this study, an improvement in the cutting stability is attempted by the reduction in the axial displacement of the tool by fastening the circular saw blade with coned disk springs. In addition, cutting state recognition system which is based on an artificial neural network is also proposed. In this system, power spectrums of the signals detected by a displacement detector and a sound-level meter are calculated to identify the cutting state. The input data of the artificial neural network are normalized by the maximum value of the power spectrum. The normarized patterns are utilized to identify whether the cutting state is stable or unstable. The vibration control system and the cutting state recognition system have been examined in cutting tests. The test results verify the effectiveness of the proposed systems for practical application.
It is known that organic substances such as oleic acid (C188H34O2) coated on work-hardened metal surface affect the decrease of cutting force and surface roughness. According to our FTIR measurement, it is presumed that these coating effects are caused by the chemisorption of oleic acid molecules to metallic atoms near dislocation. In the present research, two groups of coating materials are examined, that is, 1) liquid paraffin or ethanol containing 0.2mass% organic substances of the number of carbon being 18 (C18H38, C18H36O2, C18H35O2Na and C18H38O), and 2) liquid paraffin containing 0.2 or 100mass% carboxylic acid (CxH2xO2, x:2-18). Cutting speed and depth are 1.67mm/s and 0.02mm, respectively. The following results were obtained. 1) Cutting force is decreased by coating of 0.2mass% carboxylic acid of x??7. 2) Surface roughness were drastically improved by the coating of organic substances which the number of carbon is more than 12. 3) Cutting force is always decreased by coating of 0.2mass% organic substances of x=18 with the polarity (C18H36O2, C18H35O2Na and C18H38O).
Recently, as an electronic and an optical part with high precision are required, the research about nano technology is done very much; those are an ultra precision machining such as an ion beam machining and an ultra precision measurement such as STM technology. Nano technology is influenced from vibration and temperature change of the device and around the device. However, the research in order to reduce an ambient temperature fluctuation and the thermal drift of the device is not done very much. On the other hand, in the 21st century, it is also important to be careful on conservation of energy for protecting the earth. Therefore, in this report, a shelter with conservation of energy for supporting high precision machining was developed. At first, some properties of isolator using two kinds of styrol foams are investigated for shelter design. Next, a simple shelter using those styrol foams is manufactured. At last, in the experiment, temperature fluctuation and heat transfer coefficient fluctuation in the shelter were measured, and the thermal stability in the shelter was evaluated. It is concluded from the results that (1) the proposed shelter structure are very effective in order to reduce ambient temperature fluctuation. (2) the developed shelter is useful for supporting high precision machining and measurement. (3) this shelter is very simple, easy and low cost for setting, and running cost isn't need.
In order to reveal the mechanism of the electrochemical etching process in ultrapure water, first-principles molecular -dynamics simulations for etching process of the hydrogen-terminated Si(001) surfaces by hydroxyl ion in ultrapure water were carried out on the basis of the Kohn-Sham local-density-functional formalism. A plane-wave basis set and a norm-conserving pseudopotential were used. The standard molecular-dynamics method for the optimization of the ionic system and the steepest-descents (SD) method for the quenching procedure of the electronic degrees of freedom were adopted. It was confirmed that the chemisorbed four hydroxyl ions on the hydrogen-terminated Si(001) step edge decrease the covalent bond strength of Si-Si back-bond and initiate the etching process.
The sideward curl of chip is one of the factors by which the chip geometry can be determined, and plays a very important part in chip control. In finish cutting, especially, it is important to control the sideward curl of chip for improvement of chip breaking because chip is hardly curled upward. In this paper, the relation between sideward curl radius of chip and cutting conditions are investigated experimentally, and the cause of sideward curl formation is also discussed. Main results are as follows: (1) Sideward curl radius decreases most remarkably as the depth of cut decreases. (2) The effect of corner radius of tool on sideward curl of chip is remarkable when depth of cut is small. (3) The causes of sideward curl formation are the side flow of chip to be formed at the free edge of chip and the interference of the chip to be formed at the corner of tool.
In order to reveal the mechanism of the electrochemical etching process in ultrapure water, first-principles molecular-dynamics simulations for the etching process of hydrogen-terminated Si(001) surfaces interacting with OH molecules were carried out on the basis of the Kohn-Sham local-density-functional formalism. A plane-wave basis set was used, and the cut-off energy is 327eV(24Ry). A norm-conserving pseudopotential was also used. The standard molecular-dynamics method for the optimization of the ionic system and the preconditioned conjugate-gradient (CG) method for the quenching procedure of the electronic degrees of freedom were adopted. The optimized ionic configurations, local density of states, and atomic and bond populations for OH chemisorbed Si(001) surfaces were determined and the electronic structures relevant to the etching mechanism were clarified. It was confirmed that the interaction between two OH molecules and the hydrogen-terminated surface silicon atom on the step edge breaks the Si-Si back-bond and initiates the etching process forming a SiH2(OH)2 molecule.
Milligrams of onion-like fullerenes, so-called carbon onions, have been synthesized by heating diamond clusters in inert ambient at atmospheric pressure. Diamond clusters, of which average grain size is 5nm, were heated up to 1730°C and maintained at the temperature for 1minute in argon using an infrared image furnace. Transformation of diamond clusters into onion-like fullerenes was confirmed by high-resolution electron microscopy, which showed onion-like fullerenes have a well-controlled size ranging from 5 to 10 nm. Ball-on-disk type friction testing was conducted to characterize the tribological properties of onion-like fullerenes as a solid lubricant. As a result, onion-like fullerenes have exhibited lower friction, compared with graphite powders, in both air and vacuum. This low friction property of onion-like fullerenes has been displayed on a sliding disk with lower surface roughness and higher hardness.
This paper describes the development of a new dry wire electrical discharge machining (dry-WEDM) method which is conducted in a gas atmosphere without using dielectric liquid in order to improve the accuracy of finish cutting. In dry-WEDM, since the process reaction force is negligibly small, the vibration of the wire electrode is minute. The gap distance in dry-WEDM is narrower than that in conventional WEDM using dielectric liquid, enabling dry-WEDM to realize high accuracy in finish cutting. Moreover, since there is no need to use water as dielectric liquid, there is no corrosion of the workpiece, making dry-WEDM advantageous for the manufacturing of high-precision dies and molds.
This study proposes a new machine tool based on a new type of parallel mechanism platforms. Most parallel mechanisms, which are applied to machine tools, are based on Stewart-Gough platform that is consisting of several telescopic struts. Then, a new type of parallel mechanism platforms consisting of several linear motion actuators and constant-length rods is developed. This paper describes the feature of the new platform by comparison with Stewart-Gough platform, evaluating result of its maximum acceleration, maximum feed rate, positioning repeatability, absolute positioning accuracy and static stiffness. As a result, developed platform is 6.4 times higher than Stewart-Gough platform in natural frequency of the actuator, and 4 times higher in static stiffness of the actuator.
The non-linear analysis of chatter on-set process in single degree of freedom developed in the 1st report is further extended to chatter vibration with multiple mode coupling in actual engine lathes. The impulse excitation technique during actual turning is improved to obtain the non-linear variations of vibration parameters mi, ki, ci in each mode direction with applied load. The chatter on-set is then simulated by solving numerically the simultaneous vibration equation of mode coupling with taking both the variable mi, ki, ci obtained and the non-linearity of dynamic cutting process into account. The predicted stability thresholds of chatter vibration through the simulation are in good quantitative agreement with the experimental results which include the well known non-linear phenomena such as high feed and high speed stabilities of chatter and the finite amplitude chatter vibration.
Wear performances of CVD (Chemical Vapor Deposition) diamond films caused by PWB (Printed Wiring Board) drilling were investigated. For glass epoxy resin boards, only major cutting edge wear occurred, and chisel edge wear, margin wear, and face wear were very little. By the wear of CVD diamond films, major cutting edge showed "knife edge shape". These phenomena are very characteristic as compared to carbide drills. On the other hand, for paper phenol resin boards, almost all wear didn't occur. It is considered that the main influence factor for wear of CVD diamond films is not abrasive but thermal. Chipping of major cutting edge was triggered by appearance of substrate followed by the extension of major cutting edge wear. Wear performances were affected by a film thickness and cutting conditions. It was revealed that there were critical thickness for chipping of major cutting edge, and low feed rates accelerated wear progress.