• Transactions of the Korean Society of Mechanical Engineers A
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• v.21 no.8
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• pp.1298-1310
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• 1997

In recent years, grinding techniques for precision machining of brittle materials used in electric, optical and magnetic parts have been improved by using superabrasive wheel and precision grinding machine. The completion of optimum dressing of superabrasive wheel makes possible the effective precision grinding of brittle materials. However, the present dressing system cannot have control of optimum dressing of the superabrasive wheel. In this study, a new system and the grinding mechanism of optimum in-process electrolytic dressing were proposed. This system can carry out optimum in-process dressing of superabrasive wheel, and give very effective control according to unstable current and gap increase. Therefore, the optimum in-process electrolytic dressing is a good method to obtain the efficiency and mirror-like grinding of brittle materials.

• Journal of the Korean Society for Precision Engineering
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• v.20 no.7
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• pp.70-77
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• 2003

The centerless through-feed grinding is performed by passing the workpiece between the grinding wheel and the regulating wheel. So, the amount of removed material around the leading end, of the workpiece is always more than that around the trailing end until the leading end leaves the grinding wheel. Because of this, there are differences in diameters along the workpiece axis during grinding, and workpiece axis is not parallel to the grinding wheel axis and the contact lines between the workpiece and wheels. Thus the ground workpiece shows tapering error inherently. To eliminate this error, the workpiece axis must be kept to be parallel to the grinding wheel axis. And, the direction of the workpiece axis can be controlled by the work-rest blade. Therefore, the effects of work-rest blade inclination angle on the through-feed centerless ground part are investigated in this study. As a result, it is found that there is a positive inclination angle of the work-rest blade for minimizing the tapering error of a ground workpiece.

• Journal of the Korean Society for Precision Engineering
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• v.16 no.3 s.96
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• pp.103-108
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• 1999

A problem in the grinding with a small diametric wheel is the decrease of wheel speed. In order to resolve this problem, an accelerating unit which increases the wheel speed is recommended. In this paper, the accelerating effect of an accelerating unit has been investigated through the side-cut grinding experiments performed with a vitrified bonded CBN wheel in a machining center(MC). The static stiffness, normal force, and machining error were measured in the experiments. As the accelerating unit is attached on the column of machining center, the static stiffness of tool system is largely decreased. But as the wheel speed increased by the accelerating unit, this problem is overcome and machining efficiency is improved. The lesser the quill stiffness was, the higher the accelerating effect became.

• Transactions of the Korean Society of Automotive Engineers
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• v.21 no.2
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• pp.9-16
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• 2013

The comparisons of performance characteristics between the super-mirror face grinding machine using variable air pressure developed in this laboratory to grind precisely the sliding face of a surface hardened workpiece with thermal spray and the conventional one are investigated by measuring the surface roughness and hardness for a SCM440. To process variously workpiece according to shape, size and materials, the rotating and contacting forces of the developed grinding machine can be changed by air pressure. The surface roughness of processed workpiece can be also attained to state of mirror face by grinding precisely the sliding face with changing the rotating speed of diamond wheel. It is possible to be attached to the various machine tools because the super-mirror face grinding machine using variable air pressure is a small size. The grinding efficiency is elevated because it can be worked by two or more grinding machines attached to concurrently a machine tool for the large workpiece. In this study, results show that the cusp height of the super-mirror face grinding machine for the particle size of 100 and $1500No./mm^2$ is lower than that of the conventional one because the vibration is reduced by rotating very fast the diamond wheel with a pressed air and it can be processed by rotating the diamond wheel with a constantly varied air pressure perpendicular to workpiece surface, and that the workpiece in the super-mirror face grinding machine for the particle size of $3000No./mm^2$ can be processed to state of mirror face that is rarely seen by the cusp height. It is also found that the surface hardness of both the conventional and the super-mirror face grinding machines are increased as the particle size of diamond wheel is reduced, and the surface hardness of the super-mirror face grinding machine is HRC 1.1 ~ 1.8 higher than that of the conventional one.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.21 no.9
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• pp.1531-1540
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• 1997

Mordern industrial society pursues unmanned system and automation of manufacturing process. Abreast with this tendensy, production of goods which requires advanced accuracy is increasing as well. According to this, the work sensing time of dressing by monitoring and diagnosing the condition of grinding, which is th representative way in accurate manufacturing, is an important work to prevent serious damages which affect grinding process or products by wearing grinding wheel. Computer vision system was composed, so that grinding wheel surface was acquired by CCD camera and the change of cutting edge ratio was measured. Then we used automatic thresholding technique from histogram as a way of dividing grinding cutting edge from grinding surface. As a result, we are trying to approach unmanned system and automation by deciding more accurate time of dressing and by visualizing behavior of grinding wheel by making use of computer vision.

• Transactions of the Korean Society of Mechanical Engineers
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• v.18 no.10
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• pp.2514-2522
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• 1994

The mirror surface grinding of carbon fiber reinforced plastics(CFRP) was realized by using the metal bonded super-abrasive micro grain wheel with electrolytic in-process dressing(ELID). The maximum surface roughness $R_{max}$ of CFRP which was obtained with #6,000 wheel, was 0.65 $\mu{m}$, which was rougher surface finish compared to those of hard and brittle materials with the same mesh number wheel with ELID. The grinding performance was much dependent on the grinding direction and the best surface roughness was obtained at $90^{\circ}C$ grinding with fiber direction. The spark-out effect on the surface improvement was significant when smaller mesh number grinding wheels were used. From the surface observations of CFRP with scanning electron microscope(SEM) and Auger electron spectroscopy(AES), it was found that the mirror surface grinding of CFRP was generated by the homogenization due to carbonization of the ground surface and smearing of chips composed of the carbon fiber and carbonized epoxy resin into the ground surface.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2002.10a
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• pp.70-73
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• 2002

Using zirconium ceramics makes the ferrule, which is the part of optical communications. The quality of optical communications is directly affected by the concentricity of the optic ferrule. The products of optic ferrule should be meet the following general conditions which are the outer diameter of 2.5mm and the inner diameter of 0.125mm, and high quality conditions which are the concentricity of 0.1~$0.3\mu\textrm{m}$, the form accuracy of $0.2\mu\textrm{m}$, the roundness and the cylindricity of $0.1\mu\textrm{m}$ and the surface roughness of 10nm. Generally, the diamond wheel is used for the high efficiency and precision grinding of the materials. It is good for keeping the shape as it has little wear. Because of the loading phenomena, however, it is difficult to keep the fresh surface of the wheel. In grinding process, grinding fragments resemble fine powders rather than chips. It can easily get attached to the wheel surface and thus cause a loading. The loading takes place, in which the impurities stick to the wheel surface, and the grinding characteristics of wheel is deteriorated. To prevent all of these, a suitable dressing method should be used for the wheel. In this research, the dressing system fur co-axial grinding machine was designed and produced for the machining of ferrule, which is a high performance part. The performance of the developed dressing system was evaluated by measuring the form accuracy of ferrule, which is machined by the dressed wheel in developed dressing system.

• Journal of the Korean Society for Precision Engineering
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• v.3 no.2
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• pp.55-61
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• 1986

The study is concerned with the investigation of grinding factor affecting the AE Source by means of the relation between the amplitude level of AE signal and the depth of wheel engagement in surface grinding by AE method. As the result, work velocity was confirmed that the amplitude of AE signal had almost constant value in comparison with the depth of wheel engagement. But the depth of wheel engagement and the width of wheel engagement were proportional to the amplitude of AE signal. Therefore, when the AE Source was classified by 3-zone, Ws and Wf were affected by the depth of wheel engagement and that Wr was affected by the width of wheel engagement. Also, the adaptability of the AE method was studied about the detection of tool life of grinding wheel, sparkout and initial contact point.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 1999.10a
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• pp.498-501
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• 1999

Grinding machine rotating at high speed express the unbalance by the spindle and the weight of grinding wheel. Therefore, the parts requiring a precision processing for grinding machine need acutely to establish of automatic balancer. But the more wheel speed increases the more vibration amplitude increases, surface roughness show the satisfactory according to increase of the wheel speed. Surface roughness of the occasion installing the automatic balancer made better than an occasion no installing the automatic balancer.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1997.04a
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• pp.905-909
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• 1997

A geometric error of machine parts is one of the most important factors that affect the accuracy of positioning, generating and measuring for precision machinery. It is known that the thermal deformation of a workpiece during surface grinding is the most important in the geometric error of ground surface. This paper experimentally describes the grinding characteristics of creep-feed grinding. The wheels have 6 slotted pieces in order to compare the grinding temperature with the geometric.