• Proceedings of the Korean Society of Precision Engineering Conference
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• 1995.04b
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• pp.52-57
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• 1995

In order to suggest the proper cutting conditions of the CNC milling machining for the free-from surface, some experiments were carried out. In experiments, the influence of cutting conditions on the inclined spherical surface were examined by geometrical anlysis. In thos study, the roundness and cutting force were measured to know the effect of several cutting conditions on the machined surface and the cutting characteristics were carefully investigated. As the result, it was appeared that rigidder tool must be used and the cutting speed must be maintained constantlyfor more effective machining. It can be also known from the experiments that the improved machining surface obtained under about 80 degree, but coarse surface obtained over about 80 degree because of the existance of immproper shape of ball-end mill at the extreme portion.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2006.05a
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• pp.565-566
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• 2006

High speed machining experiment on the inclined surfaces of hardened mold steel(STAVAX at hardness HRC 53) is carried out using the long-neck type ball endmill. Surface texture and roughness are compared fur various cutting conditions. Tool overhang length greatly affects the roughness of machined surface. It is found that, fur this type of long-neck endmill, the chip load should be carefully selected by reducing either the axial depth of cut or feedrate to avoid tool vibration. Feedrate adjustment is more appropriate method in terms of tool wear.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 2000.10a
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• pp.262-267
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• 2000

During the turning of the workpiece, cutting heat causes thermal deformation of the cutting tool which influences the surface characteristics of the machined part. This paper presents a study of thermal deformation of the cutting tool. For this purpose, cutting tool is modeled based on Pro/Engineering and temperature and deformation are simulated by means of the finite element method. The thermal effect on the surface roughness profile is simulated by using surface-shaping system.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.17 no.5
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• pp.70-75
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• 2018

This study analyzes the change of Al 6061-T6 specimen surface shape when undergoing microparticle spraying and analyzes the influence of factors on the experiment. Fine particle spraying is applied to the specimen and the surface shape of the processed surface is measured through a surface shape measuring device. The measured data was analyzed by the ANOVA method to investigate the effect of factors such as particle, nozzle diameter, pressure, injection height, and injection time on the injection depth and injection diameter.

• The Journal of the Korean dental association
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• v.46 no.8
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• pp.494-504
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• 2008

Osseointegration is a result of bone formation and bone regeneration process, which take place at the interface between bone and implant and biologic determinants such as cytokine, growth factors, bone matrix proteins play an important role in osseointegration. The purpose of this study is to compare the expressoin of TGF-$\beta$, IGF-I, BMP2, BMP4 during osseointegration. We designed an experimental group which was inserted with a RBM surface titanium implants and machined surface, and compared with a control group which had a simple bone cavity and normal bone. Titanium implants were placed into tibia of 8 rabbits. We compared the expression of TGF-$\beta$, IGF-I, BMP2, BMP4 using RT_PCR (reverse transcriptase chain reaction)analysis in day 3,7,14 and 28 of implant insertion. According to the results, growth factors of experimental groups were more expressed than control groups. Among experimental groups, expression of TGF-$\beta$, IGF-I, BMP4 of BMP group had tedency to increase more at 14th, 28th days than Machined surface group. Therefore, our results suggest that TGF-$\beta$, IGF-I, BMP4 are expressed within the bone around the implant and more increased around rough surface implants while osseointegration occurs after dental implant insertion.

• Design & Manufacturing
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• v.1 no.1
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• pp.7-11
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• 2007

The fabrication of precision optical components by deterministic CNC grinding is an area of great current interest. Replacement of the traditional, craftsman driven, optical fabrication process is essential to reduce costs and increase process flexibility and reliability. Moreover, CNC grinding is well suited to the fabrication of complex shapes such as aspheres, making it possible to design optical systems with fewer components and reduced weight. Current technology is capable of producing surfaces with less than 2 microns peak to valley error, 50 nm rms surface roughness, and less than 1 micron subsurface damage. Bound abrasive tools, in which the abrasive particles are fixed in a second (matrix) material, play an important part in achieving this performance. In this paper, the factors affecting the ultra-fine surface roughness and profile accuracy of machined surfaces of aspheric parts has been analyzed experimentally and theoretically and on ultra-precision aspheric grinding system and precise adjusting mechanism have been designed and manufactured. In the paper we report the results of experiments and modeling performed to examine the effects of machinability, occurring during grinding of optical surfaces, on the tool surface profile. Profiles of machined surface were measured by using SEM. In order to optimize grinding conditions of aspheric lens processing, we performed experiments by design of experiments.

• Journal of the Korean Association of Oral and Maxillofacial Surgeons
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• v.37 no.3
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• pp.214-224
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• 2011

Objective: This study examined the potential of the in vitro osteogenesis of microtopographically modified surfaces, RBM (resorbable blasting media) surfaces, which generate hydroxyapatite grit-blasting. Methods: RBM surfaces were modified hydroxyapatite grit-blasting to produce microtopographically modified surfaces and the surface morphology, roughness or elements were examined. To investigate the potential of the in vitro osteogenesis, the osteoblastic cell adhesion, proliferation, and differentiation were examined using the human osteoblast-like cell line, MG-63 cells. Osteoblastic cell proliferation was examined as a function of time. In addition, osteoblastic cell differentiation was verified using four different methods of an ALP activity assay, a mineralization assay using alizarin red-s staining, and gene expression of osteoblastic differentiation marker using RT-PCR or ELISA. Results: Osteoblastic cell adhesion, proliferation and ALP activity was elevated on the RBM surfaces compared to the machined group. The cells exhibited a high level of gene expression of the osteoblastic differentiation makers (osteonectin, type I collagen, Runx-2, osterix). imilar data was represented in the ELISA produced similar results in that the RBM surface increased the level of osteocalcin, osteopontin, TGF-beta1 and PGE2 secretion, which was known to stimulate the osteogenesis. Moreover, alizarin red-s staining revealed significantly more mineralized nodules on the RBM surfaces than the machined discs. Conclusion: RBM surfaces modified with hydroxyapatite grit-blasting stimulate the in vitro osteogenesis of MG-63 cells and may accelerate bone formation and increase bone-implant contact.

• Journal of Periodontal and Implant Science
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• v.31 no.2
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• pp.451-463
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• 2001

Following the extensive use of implant, the incidence of peri-implantitis increases. Guided bone regeneration has been used for the optimal treatment of this disease. Because implant surface was contaminated with plaque and calculus, cleaning and detoxification were needed for the reosseointegration when guided bone regeneration was performed. Various mechanical and chemical methods have been used for cleaning and detoxification of implant surface, air-powder abrasive and oversaturated citrate were known to be most effective among these methods. However, these methods were incomplete because these could not thoroughly remove bacteria of implant surface, moreover deformed implant surface. Recent studies for detoxification of the implant surface using laser were going on, $CO_2$ laser and Soft Diode laser were known to be effective among these methods. The purpose of this study was to obtain clinical guide by application these laser to implant surface. 15 experimental machined pure titanium cylinder models were fabricated. The $CO_2$ laser treatment under dry, wet and hydrogen peroxide condition or the Soft Diode laser treatment under Toluidine blue O solution condition was performed on the each of models. Each groups were examined with SPM and SEM to know whether their surface was changed. The results were as follows : 1. Surface roughness and surface form weren't changed when $CO_2$ laser was usedunder dry condition(P>0.05). 2. Surface roughness and surface form weren't changed when $CO_2$ laser was used under wet condition(P>0.05). 3. Surface roughness and surface form weren't changed when $CO_2$ laser was used under hydrogen peroxide condition(P>0.05). 4. Surface roughness and surface form weren't changed when Soft Diode laser was used under toluidine blue O solution condition(P>0.05). From the result of this study, it may be concluded that the $CO_2$ laser having relatively safe pulse mode and the Soft Diode laser used with photosensitizer can be used safely to treat peri-implantitis.

• Design & Manufacturing
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• v.11 no.2
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• pp.51-56
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• 2017

Nitinol, a shape memory alloy (SMA), is manufactured from titanium and nickel and it used in various fields such as electrical applications, micro sensors. It is also recommended as a material in medical for implant because it has excellent organic compatibility. Nitinol is intended to be inserted into the human body, products require a high-quality surface and low residual stress. To overcome this problems, explore electrolyte polishing (EP) is being explored that may be appropriate for use with nitinol. EP is a particularly useful machining method because, as a non contact machining method, it produces neither machining heat nor internal stress in the machined materials. Sandpaper polishing is also useful machining method because, as a contact machining method, it can easily good surface roughness in the machined materials. The electrolyte polishing (EP) process has an effect of improving the surface roughness as well as the film polishing process, but has a characteristic that the residual stress is hardly generated because the work hardened layer is not formed on the processed surface. The sandpaper polishing process has the effect of improving the surface roughness but the residual stress remains in the surface. We experimented with three conditions of polishing process. First condition is the conventional polishing. Second condition is the electrochemical polishing(EP). And Last condition is a mixing process with the conventional polishing and the EP. Surface roughness and residual stress of the nitinol before a polishing process were $0.474{\mu}mRa$, -45.38MPa. Surface roughness and residual stress of the nitinol after mixing process of the conventional polishing and the EP were $1.071{\mu}mRa$, -143.157MPa. Surface roughness and residual stress of the nitinol after conventional polishing were $0.385{\mu}mRa$ and -205.15MPa. Surface roughness and residual stress of sandpaper and EP nitinol were $1.071{\mu}mRa$, -143.157MPa. The result shows that the EP process is a residual stress free process that eliminates the residual stress on the surface while eliminating the deformed layer remaining on the surface through composite surface machining rather than single surface machining. The EP process can be used for biomaterials such as nitinol and be applied to polishing of wafers and various fields.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.7 no.1
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• pp.34-40
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• 1998

Conductive metal matrix composite(MMC) material of 30% silicon carbide particulated based on aluminum matrix was machined by die sinking electrical discharge machining(EDM) process according to different current and duty factor for reverse polarity of electrode. Material removal rate(MRR) was examined by process under various operation conditions. The surface morphology was evaluated by surface roughness parameter and scanning electron microscopy(SEM) research. The MRR was suddenly increased over 11 ampere of current, and it was slightly changed over 0.3 of duty factor. The maximum surface roughness of EDMed surface was affected by the duty factor. The SEM photograghs of EDMed surface showed wide recast distribution region of melting materials as increased of current and duty factor.