• Proceedings of the Korean Society of Precision Engineering Conference
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• 2002.10a
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• pp.291-295
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• 2002

Ceramics are very difficult-to-cut materials because of its high strength and hardness. Their machining process can be characterized by cracking and brittle fracture. Generally, ceramics are machined using traditional method such as grinding and polishing. However, such processes are generally costly and have low material removal rate. In this paper, to develop machinable ceramics those have good machinability without losing their material properties, machinability evaluations are performed by applying the experimental design method. In this paper, to evaluate the machinability of the developed ceramics, various workpieces are machined on the CNC machining center, and surface roughness are measured under predefined process parameters obtained using Taguchi method. And the experimental results are investigated to derive optimum cutting parameters for the given materials.

• Transactions of the Korean Society of Machine Tool Engineers
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• v.10 no.6
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• pp.109-115
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• 2001

This paper investigates the mechanical characteristics of angle-ply laminates with non-woven carbon tissue. The lami- nates were made by inserting non-woven carbon tissue at the interface. Specimens were rounded near the tabs by grinding and polishing to reduce the stress concentration. Cyclic loads were applied to the specimens and the stress and fatigue life curves were obtained. The matrix crack density was also evaluated to check the effects of non-woven carbon tissue on the fracture resistance of composite laminates. C-Sean technique was used to evaluate the delamination, and SEM was used to understand the fracture mechanisms of the laminates. Experimental results show that the fatigue strength and life of composite laminates were increased by inserting non- woven carbon tissues. The results also show that the matrix crack density and delamination area were reduced by inserting non-woven carbon tissues.

• Journal of the Optical Society of Korea
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• v.11 no.3
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• pp.85-92
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• 2007

In the past, precision optical glass lenses were produced through multiple processes such as grinding and polishing, but mass production of aspheric glass lenses requiring high accuracy and having complex profile was rather difficult. In such a background, the high-precision optical glass molding pressing (GMP) process was developed with an eye to mass production of precision optical glass parts by molding press. In this paper, as a fundamental research to develop the multi-cavity mold for higher productivity of a progressive GMP process used in the fabrication of an aspheric glass lens, an aspheric glass lens forming simulation was carried out.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2000.11a
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• pp.583-586
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• 2000

The non-selective method by polishing after grinding was used widely to thinning of SDB SOI structures. This method was very difficult to thickness control of thin film, and it was dependent on equipments. However electrochemical etch-stop, one of the selective methods, was able to accurately thickness control and etch equipment was very simple. Therefore, this paper described with the effect of leakage current and electrodes on electrochemical etch-stop. Consequentially, PP(passivation potential) was changed according to the kinds of contact and contact sizes, but OCP(open current potential) was not change with range of -1.5~-1.3V

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1992.10a
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• pp.115-120
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• 1992

Mirror-surface machining is very important machining technology to manufacture optical parts. especially brittle materials. In case of optical plastics, it is produced through both grinding and polishing till now. New machining method which is more efficient and contributed to the protection of the environmental pollution is, therefore, studied. In this , experimental results and an analysis of surface roughness in ultrasonic vibration cutting of optical plastic (CR-39) which is used for optical lens is presented. In results, a comparison of the micro-structure of machined surfaces produced by cutting with ultrasonic vibration and conventional turning is presented by analyzing S.E.M. photograph. Also, wavelength spectrum analysis is performed to investigate the surface-characteristics machined by ultrasonic vibration cutting.

• Proceedings of the Korean Society Of Semiconductor Equipment Technology
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• 2003.05a
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• pp.18-22
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• 2003

The sapphire wafers for blue light emitting devices were manufactured by the implementation of the surface machining technology based on micro-tribology. This process has been performed by grinding, lapping and polishing. The surfaces of sapphire wafers were mechanically affected by residual stress and surface default. This mechanical stress and strain can be cured by thermal anneal ing process. The sapphire crystalline wafers were annealed at $1100~1400^{\circ}C$ and then characterized by double crystal X-ray diffraction. The sample showed good quality of crystalline wafer surface wi th full width at hal f maximum of 16 arcsec for the 4-hour heat-treatment at $1300^{\circ}C$.

• Journal of Industrial Technology
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• v.17
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• pp.5-10
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• 1997

Fatigue tests were performed to investigate how much vary the fatigue limit under the different surface conditions on Carbon Steel(SM55C). Four types of specimen which have different surface roughness each other, Series A by turning, Series B by grinding, Series C by polishing and Series D by roller finishing showed the fatigue limit of 265, 320, 335 and 365MPa, respectively. Series D show 36% higher than Series A, which is caused by compressive residential stress on the surface. Therefore, roller finishing machining is helpful not only increase the fatigue limit but also improve the surface roughness. Moreover, to predict the fatigue limit under the conditions of knowing surface roughness and hardness of specimen, ${\sqrt{area}}$ area parameter method is very useful.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2004.10a
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• pp.1348-1352
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• 2004

An aspherical lens in information technology has been increased in order to enhance the optical performances. There are two kinds of approaches to machine the aspherica surface is generally conducted by the diamond turning machine, precision grinding machine, and polishing machine. This technique, however, has a problem which needs an expensive and high precision machine in order to increase the surface roughness and the machining accuracy. In this paper, a machine, which is able to machine the aspherical surface, was developed to decrease the cost. Also, the machining of the aspherical surface using a cone was carried out experimentally in order to compare the experiment with the simulation. The results showed that the machining experiments of the aspherical surface by using the titled cone were in accordance with the simulation.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2003.06a
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• pp.1257-1260
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• 2003

Rapid Prototyping technology has many advantages such as Rapid Tooling. However, Using the RT technique is limited by the poor surface quality of the RP part. Thus, additional post-machining is required for improving the surface roughness by the sanding, grinding and polishing etc. But, these traditional finishing techniques are time and labor cost consuming. Hence, improving and formulation the finishing technique is inevitably necessary for the RF part. A new post-machining methodology for RP part is presented by the SLS part is used for automobile components in this research. Also, a web based interface tool that user requirements are rapidly ordered for post-machining RP part is developed.

• Journal of the Korean Society for Precision Engineering
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• v.11 no.1
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• pp.177-183
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• 1994

The ball-end milling process is widely used in the die/mold industries, and it is very suitable for the machining of free-from surfaces. However, cusps(or scallops) remaining at the machined part along the cutter paths require anothe finish process such as polishing or grinding. In this study, a high sped micro ball-end milling method has been suggested for the finish of free- form surfaces. A new tool path which makes the geometrical roughness of workpiece be constant through the machined surface has been developed. In the high speed machining of micro ball-end muling experimets, the developed tool paths have been successfully applied. And it was concluded that the surface roughness from this finish cuts of micro ball-end milling process was acceptable.