Katsuo Syoji

Ductile regime turning at large tool feed

Ductile regime turning is a new technology for obtaining a crack-free surface on brittle material. However, the fundamental obstacle for industrial application of this technology is diamond tool wear. This problem is difficult to solve for existing methods of turning with roundnosed tools due to limitation on tool feed. In this paper, ductile regime turning using the straight-nosed diamond tool is proposed. This method enables thinning of undeformed chip thickness in the nanometric range and at the same time provides significant cutting width ensuring plain strain conditions. Adopting a small cutting edge angle enables ductile regime turning at a large tool feed up to a few tens of micrometers. Single crystal silicon is machined and chip morphology and machined surface texture are examined for clarifying the brittle‐ductile transition mechanism. Ductile surface with nanometric roughness is obtained and generation of plastically deformed continuous chips is confirmed. # 2002 Elsevier Science B.V. All rights reserved.

A new grinding method for aspheric ceramic mirrors

Abstract This paper reports the development of an ultra-precise grinding system based on a new grinding technique called the “Arc Envelope Grinding Method (AEGM)”. AEGM, which is used for grinding aspheric ceramic mirrors, increases both wheel life and grinding performance, and significantly decreases total production costs. The necessary instrumentation and control system of our new instrument that utilizes AEGM have been designed and built. The tool path was calculated on a supercomputer, and the CNC program generation and tool path compensation were performed on a PC linked to the same supercomputer. Using this grinding system, aspheric mirrors of glass and silicon carbide, 100 mm in diameter, were successfully ground. The form error after the first grinding (without any compensation) was less than 1.8 μm, and the roughness was R max = 82 nm ( R a = 10 nm).

Electrorheological fluid-assisted ultra-precision polishing for small three-dimensional parts

This paper deals with a new machining method (electrorheological fluid-assisted polishing) for small three-dimensional parts such as micro-aspherical lens, die and mirror. The behavior of electrorheological particles and abrasive particles in the vicinity of the tip of the tool was observed by CCD microscope, and the electric field strength, electrode shape, and type of abrasive particles were investigated. It was clear that the electrorheological effect facilitates collection of the abrasive particles at the tool tip, even while the tool is rotating. Then, electrorheological fluid-assisted micro-aspherical generator system was developed, which is capable of micro-grinding and micro-polishing on the same machine. The system demonstrated the excellent polishing performance of small area after grinding process.

Crystallographic effects in micro/nanomachining of single-crystal calcium fluoride

Single-crystal calcium fluoride (CaF2) is an excellent optical material in the infrared range and the ultraviolet range. It is an indispensable substrate material for the 193 and 157 nm wavelength laser optics for future large-scale semiconductor photolithography systems. Due to its delicate nature, for the most part the CaF2 elements have been fabricated using conventional pitch polishing combined with interferometry and local surface correction to form the desired flat, sphere or aspherical surface. In the present work, the feasibility of generating high quality optical surfaces on CaF2 by single-point diamond turning is examined. The development of this technology may provide the possibility of fabricating aspherical and diffractive optical components in an efficient way. The machining experiments described in this article were done on a high-stiffness, ultraprecision, numerically controlled diamond lathe with a sharply pointed single-crystal diamond tool. The scale of machining was varied from the mic...

A New Centerless Grinding Technique without Employing a Regulating Wheel

A new centerless grinding method without a regulating wheel is pr oposed. Instead of using a regulating wheel, this method employs an ultrasonic vibrating shoe t o support the workpiece. The end of the vibrating shoe is in an elliptic motion at a high frequency, while the rotational speed of the workpiece is controlled by the elliptic motion of the shoe. An experime ntal apparatus has been designed and constructed. Tests involving the rotational drive of a workpiec e were then conducted on the apparatus, which showed that the workpiece rotational speed depends on the AC voltage and the frequency. Finally, grinding tests involving pin-shaped workpieces with an initial roundness of 20 μm were performed. The results show that the roundness of the workpieces w as improved to 1.5 μm after grinding using the new apparatus.

Determination of an Optimum Geometrical Arrangement of Workpiece in the Ultrasonic Elliptic-Vibration Shoe Centerless Grinding

This paper clarifies the influence of the geometrical arrangement of the workpiece on workpiece roundness in the ultrasonic elliptic-vibration shoe centerless grinding, and determines an optimum geometrical arrangement for minimizing the roundness error of the workpiece. The influence of the geometrical arrangements ( , , ) of the workpiece on workpiece roundness were investigated by computer simulation involving a cylindrical workpiece of 5 mm in diameter with an initial roundness error of 25 μm. The results indicated that the final roundness error of the workpiece after grinding reaches a minimum at + =7° for various values of . It was found that the smaller the blade angle , the more precise the workpiece in terms of final roundness. Practical grinding operations involving pin shaped workpieces, such as SKH51, 5 mm in diameter and 15 mm in length, were carried out on the experimental apparatus previously developed. The experimental results agreed closely with those obtained by the simulation, showing that the optimum geometrical arrangement of the workpiece can be determined at + =7° and =60°, in which the workpiece roundness was improved from an initial roundness error of 25 μm to the final one of approximately 0.6 μm.

Nano-Topography Characterization of Axisymmetrical Aspherical Ground Surfaces

There is nano-topography on axisymmetric aspherical ground surfaces. Usually, the axisymmetric aspherical lens or molding dies are finished by poli shing after they are machined by grinding. However, nano-topography cannot be removed by polishing. Nano-topography caus es grinding marks, which lowers the accuracy of optical instruments such a s lenses. In this research, the formation mechanism of nano-topography on axisymmetric ground surfaces a nd rel tionship between the topography and grinding conditions is analyzed theoretically. The res ults show that the vibration of the grinding wheel causes nano-topography. In addition, grinding marks chang es with the variation in the grinding wheel revolution speed and the workpiece revolution speed. Introduction Axisymmetric aspherical lenses or molding dies are m achined by grinding and finished by polishing. The surface roughness is smoothed with polishing. H owever, polishing cannot eliminate the surface waviness— that is, the nano-topography—that is gene rated by the grinding process. Nano-topography causes the grinding marks, which lowers the accurac y of optical instruments such as lenses. In additio n, the nano-topography measures approximately 30 nm. Be caus the form accuracy of an axisymmetric aspherical surface is approximately 100 nm, nano-top graphy size can adversely affect form accuracy. If the pattern of the nano-topography is controllab le, i.e., removable, it can be controlled by polishing. There fore, to attain the goal of increased accuracy, nano-topogra hy should be controllable. In our research, we apply theory a nd simulation to analyze the relationship between the grinding conditions and grinding marks caused by nano-topogr aphy. Generation Mechanism of Grinding Marks Figure 1 is a photograph of the grinding marks on an axisymmetric aspherical ground surface. The grinding marks, which consist of concentric circle patterns and whirling patterns, are apparent. We found that the cause of the grinding marks in high-speed reciprocation grinding is the vibration of the grinding wheel [1]. Therefore, we believe that the cause of grinding marks in axisymmetric aspherical grinding is also the vibration of the grinding wheel. Figure 2 shows a grinding mark formation model in axisymmetric grinding. In this model, the workpiece rotates at a constant frequency fw and is Fig. 1 Photograph of grinding marks Fig. 2 Formation model of grinding marks Key Engineering Materials Online: 2003-04-15 ISSN: 1662-9795, Vols. 238-239, pp 125-130 doi:10.4028/www.scientific.net/KEM.238-239.125

Development of a Polishing Disc Containing Granulated Fine Abrasives

Polishing technology has provided the possibility of obtaining super smooth surfaces on semiconductor and other brittle materials for electronic and optical applications. In this study, a new manufacturing method for a polishing disc with fixed fine abrasive grains is proposed. This manufacturing method consists of three main processes. In the first process, an undiluted solution of abrasives is produced by adding some sodium alginate into the solution in which fine abrasive grains of SiO2, Al2O3 and Cr2O3 are dispersed. Next, by dropping the undiluted abrasive solution into a lactic acid calcium solution, the fine abrasive grains are granulated into spheres having diameters of 2-3 mm. In the second process, the granulated spheres are combined using the same undiluted abrasive solution as a binder. In the last process, the combined body of granulation spheres is dried up and formed by a lathe. The polishing disc produced by this method has a bulk density of 0.5g/cm, a Vickers hardness less than HV10. Observations using a scanning electron microscope show that the polishing disc has a high-density and homogeneous structure and the bonding strength is low. Experimental results indicate that the developed polishing disc can be used in high efficiency polishing for silicon wafers.

Nano-topography on axisymmetric aspherical ground surfaces

Recently, axisymmetric aspherical lenses are being increasingly installed in optical devices such as digital cameras. As the pixel number of digital image sensors increases, both high form accuracy and fine surface roughness are required, compared with conventional products. However, distortion in an optical image occurs even if an axisymmetric aspherical lens, which has high form accuracy and fine surface roughness, is used. The distortion of the optical image is caused by the surface nano-topography, which is generated in the grinding process. In this paper, the relationship between grinding conditions and the distribution of the nano-topography is investigated. In addition, a fluctuation-free grinding machine was developed to control the nano-topography.

A Novel Form Error Compensation Technique for Tungsten Carbide Mould Insert Machining Utilizing Parallel Grinding Technology

Mould inserts with high form accuracy can be produced with ease using modem grinding technologies. However, several grinding cycles are often required to reduce the form error to an acceptable value, significantly dependent on the tool path compensation technique used. This paper reports on a novel form error compensation technique for tungsten carbide mould insert machining utilizing a parallel grinding method. In this technique, a newly developed program is used to process the profile data measured using a Form Talysurf profilometer, and to further generate the NC tool path for form error compensation. The developed technique focuses on the compensation of form error resulted by two major error sources, wheel radius and waviness errors. Using the developed technique, the initial residual form error upon the completion of primary grinding is minimized. Subsequently, the residual form error is compensated by modifying the NC tool path. With this technique, the speed of convergence of the residual form error has improved markedly. The grinding result shows that, after just one compensation cycle, a form error of approximately 0.3 mu m in PV is achieved.