• The Journal of Korean Academy of Prosthodontics
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• v.23 no.1
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• pp.155-164
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• 1985

Acrylic resin has some disadvantages in its physical properties such as a low surface hardness, being easily abraded as well as low degree of impact resistance. To overcome these disavantages, Perma Cure System was introduced in 1981, in which photo polymerizing monomers coated on acrylic resin surface were polymerized. In this study, to observe the effect of Perma Cure System on physical properties of treated surface of different types of acrylic resin, abrasion resistance, surface hardness and surface roughness of 4 different types of resin (Premium, Ortho-jet acrylic, Quick resin, Thermo jel) were tested before and after coating treatment. The conclusions arised from this study are as follows; 1. In all types of resin, the abrasion resistance of coated specimen was higher than that of uncoated specimen, and there was difference in amount of abrasion among the types of coated resin. 2. In all types of resin, the surface hardness of coated specimen was higher than that of uncoated specimen, and there was no difference in surface hardness among the types of coated resin. 3. In all types of resin, surface roughness of coated specimen was lower than that of uncoated specimen, and was different according to the degree of surface roughness before coating treatment in same sort of resin specimen.

• Proceedings of the KSME Conference
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• 2004.04a
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• pp.1148-1153
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• 2004

Recently the high speed end-milling processing is demanded the high-precise technique with good surface rougj1ness and rapid time in aircraft, automobile part and molding industry. The working factors of high speed end-milling has an effect on surface roughness of cutting surface. Therefore this study was carried out to analyze the working factors to get the optimum surface roughness by design of experiment. From this study, surface roughness have an much effect according to priority on Spindle speed, feed rale, hardness and axial depth of cut By design of experiment, it is effectively represented shape characteristics of surface roughness in high speed end-milling And determination($R^2$) coefficient of regression equation had a satisfactory reliability of 89.7% and regression equation of surface roughness is made by regression analysis.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 2004.10a
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• pp.54-59
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• 2004

A measure for good products manufactured by grinding process is the surface roughness that is affected by a lot of operating parameters such as types of abrasive, grain size, bond material, wheel speed, table speed, depth of cut, hardness of workpiece and stiffness of grinding machine. In this study, an application of the design of experiments was tried for evaluating the effect of operating parameters on the surface roughness. The workpiece was a high speed tool steel(SKH51) and the surface grinding was conducted. In order to obtain the best surface roughness within constraints of the working range, the optimal grinding conditions were selected. The usefulness of this method was evaluated by the statistical strategy.

• 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.

• Journal of the Korean Society for Precision Engineering
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• v.1 no.2
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• pp.24-32
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• 1984

The object of the study is to discuss the effect of magic ink as a surface active substance on the mechanism of chip formation in oblique cutting. The Rehbinder effect has been known as a phenomenon that the mechanical strength reduces when the metal is coated with some surface active substances. In order to interpret these surface effects defined by Rehbinder, the influence on the shear strength of shear plane by coating surface active substances, cutting force by the depth of cut, surface roughness and hardness ratio were observed. The results are as follows: 1. By coating the magic ink on free surface of the forming chip, the effective shear angle increases, and the cuttinbg force and the deformed chip thickness decreases. 2. With the large inclination angle the effective shear angle increases, and the specific cutting force and the friction angle decrease. 3. Cutting of the coated surface improves the surface roughness and the hardness ratio drops, which means another Rehbinder effect.

• Transactions of the Korean Society of Machine Tool Engineers
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• v.13 no.3
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• pp.53-60
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• 2004

We have developed and manufactured an experimental ultrasonic polishing machine with frequency of 20kHz at the power of vibration 1.7㎾ for effective ultrasonic polishing in processing of high hardness material. Design of the horn is performed by the FEM analysis. The following conclusions were empirically deduced through experimental results to clarify the major elements which affect the surface roughness during the ultrasonic process by following the experimental plans. The ultrasonic polishing machine has been developed in parts of structure part, ultrasonic generator, vibrator. We were able to process the high hardness material without difficulty as a result of ultrasonic polishing by utilizing the groove added step-type horn. Through analyzing by applying the experimental plans, the rotating speed of the horn was determined to be the major factor in influencing the surface roughness. In the case of ceramic, wafer, we were able to obtain good surface roughness when the feed rate and the ultrasonic output were higher. Because the load on slurry particle increases when the ultrasonic output is higher, the processed surface becomes worse in the case of optical glass.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.62 no.2
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• pp.284-287
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• 2013

In this work, we have fabricated TiC films by using unbalanced magnetron sputtering method with graphite and Ti targets for contact strip application of electric railway. TiC films were deposited with various substrate temperatures. We investigated various properties of TiC films prepared with various substrate temperatures, such as the hardness, surface roughness, friction coefficient, resistivity, FESEM (Field Emission Scanning Electron Microscopy), HRTEM (High Resolution Transmission Electron Microscopy) and XPS (X-ray Photoelectron Spectroscopy). The hardness and friction coefficient properties of TiC films were improved with increasing substrate temperature. These results indicate that the improvement of hardness and resistivity is related to the increase of sp2 clusters in TiC films. And also, the resistivity value of TiC films were decreased with increasing substrate temperature.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.61 no.10
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• pp.1561-1564
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• 2012

In this work, we have fabricated the nanocrystalline carbon films by using unbalanced magnetron sputtering method with graphite and Ti targets for contact strip application of electrical railway. The power density of graphite target was fixed and the power density was increased for the increase of Ti concentration in TiC films. We investigated the hardness, surface roughness, contact angle, resistivity, HRTEM and XPS of TiC films with Ti concentration. The hardness and resistivity were improved with increasing Ti concentration. These results indicate that the improvement of hardness and resistivity is related to the increase of sp2 clusters in TiC films.

• Journal of the Korean Society of Industry Convergence
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• v.5 no.4
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• pp.367-372
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• 2002

Experimental study was conducted for lapping process after WEDMed specimen. In order to decide the lapping depth of the specimen, the number of the grain size was increased from 400, 600 to 800 to obtain the better surface. Observation of scanning electron microscope, hardness test, surface roughness test and energy dispersive spectrum(EDS) analysis were used for this experimental study. From the comparison and analyses of the results of between the wire-cut electrical discharge machining and the lapping, the following results were obtained. The surface roughness after lapping was found to be improved as increasing the number of lapping process like 1st, 2nd, 3rd lapping and the number of grain size such as 400, 600, 800. The surface hardness after increasing the lapping depth of the specimen was slowly increased. It was found that after 3rd lapping process the hardness was reached the hardness of original base material. It was found that the small amount of coating components within 3% was remained after the 1st lapping process, compared to that approximately 16% after WEDM process.

• Journal of the Korean Society for Precision Engineering
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• v.22 no.2
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• pp.202-209
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• 2005

A new effective thick-layered RP process, Transfer-type Variable Lamination Manufacturing using expandable polystyrene foam (VLM-ST) has been developed with thick layers and sloped surfaces. VLM-ST has the innate advantages by virtue of its working principle: high building speed, low cost for introduction and maintenance of VLM-ST apparatus, little staircase surface irregularities of parts. Despite these advantages in VLM-ST, the surface roughness of VLM-ST parts is still inadequate to be used as RP master patterns for rapid tooling (RT). This paper describes the systematic and effective methodology to remove the laminated pattern and improve the surface roughness for VLM-ST parts. From the results of surface finishing of VLM-ST parts, it can be seen that the laminated pattern is completely removed and the surface characteristics such as surface roughness, surface hardness, and paintability are improved.