• Journal of the Korean Society of Manufacturing Process Engineers
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• v.4 no.3
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• pp.39-44
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• 2005

With the development of high speed and accuracy machining, the micro-chips are formed in the machining process and broken particles are circulated with the cutting fluid. The surface roughness and accuracy of part are deteriorated because the metal particles included in the cutting fluid are embedded on machined surface. In this study, the influences of particles for the machined surface according to filtering degrees are evaluated and the embedding mechanism is suggested.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.9 no.1
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• pp.106-113
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• 2010

The most suitable condition for plasma source ion implantation(PSII) was found based on the study of the characteristics of PSIIed tool and machined surfaces. The depth analysis according to the chemical bonding state of elements and surface component elements through the XPS and SIMS, was conducted to find the improved property of the PSIIed surface. Due to the diffusion of PSII, the nitrogen was found up to a depth of about 150nm according to the supplied voltage and ion implanted time. The deep diffusion by nitrogen caused the surface modification, but the formation of oxide component was found due to the residual gas contamination on the surface. Statistical method of ANOVA was conducted to find the effects of spindle speed and feed rate in interaction for machined surface roughness with PSIIed tools. The surface modification was found largely occurred by the nitrogen implanted surface with 2 hours for 27kV, 35kV and 43kV.

• Journal of the Korean Society for Precision Engineering
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• v.14 no.8
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• pp.101-107
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• 1997

In general, grinding is one of the final machining processes which determines the surface quality of machined products. Since the ground surface is affected by the states of grains and voids on the grinding wheel surface, the wheel should be dressed before the machined surface deteriorates over a quality limit This paper describes a systematic approach to decide a proper dressing chance and an optimal dressing depth for the working grinding wheel. An eddy current sensor and a laser displacement sensor are used to measure the loading on the working wheel surface and the topography of the dressed wheel surface respec- tively. The dressing chance can be properly decided through the relational locus between the amount of handing and the machined surface roughness. An optimal dressing depth to guarantee the less wheel loss and the higher wheel surface quality is decided through the analysis of the variance of topography for the dressed wheel surface, which decreases at three different rates according to the accumulated dressing depth.

• Journal of the Korean Society for Precision Engineering
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• v.21 no.1
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• pp.51-60
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• 2004

Ball-end milling is one of the most common manufacturing processes for the parts with sculptured surface. However, the conventional roughness model is not suitable for the evaluation of surface texture and roughness under highly efficient machining conditions. Therefore, a different approach is needed for the accurate evaluation of machined surface. In this study, a new method, named ‘Ridge method’, is proposed for the effective prediction of the geometrical roughness and the surface topology in ball-end milling. Theoretical analysis of a machined surface texture was performed considering the actual trochoidal trajectories of cutting edge. The characteristic lines of cut remainder are defined as three-types of ‘Ridges’ and their mathematical equations are derived from the surface generation mechanism of ball-end milling process. The predicted results are compared with the results of conventional method. The agreement between the results predicted by the proposed method and the values calculated by the simulation method shows that the analytic equations presented in this paper are useful for evaluating a geometrical surface roughness of ball -end milling process.

• The Journal of Korean Academy of Prosthodontics
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• v.48 no.2
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• pp.122-127
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• 2010

Purpose: The objective of this study was to investigate the effects of calcium phosphate coated titanium implant surface on bone response and implant stability at early stage of healing period of 3 weeks and later healing period of 6 weeks. Material and methods: A total of 24 machined, screw-shaped implants (Dentium Co., Ltd., Seoul, Korea) which dimensions were 3.3 mm in diameter and 5.0 mm in length, were used in this research. All implants (n = 24), made of commercially pure (grade IV) titanium, were divided into 2 groups. Twelve implants (n = 12) were machined without any surface modification (control). The test implants (n = 12) were anodized and coated with thin film (150nm) of calcium phosphate by electron-beam deposition. The implants were placed on the proximal surface of the rabbit tibiae. The bone to implant contact (BIC) ratios was evaluated after 3 and 6 weeks of implant insertion. Results: The BIC percentage of calcium phosphate coated implants ($70.8{\pm}18.9%$) was significantly higher than that of machined implants ($44.1{\pm}16.5%$) 3 weeks after implant insertion (P = 0.0264). However, there was no significant difference between the groups after 6 weeks of healing (P > .05). Conclusion: The histomorphometric evaluation of implant surface revealed that; 1. After 3 weeks early healing period, bone to implant contact (BIC) percentage of calcium phosphate coated implants (70.8%) was much greater than that of surface untreated machined implants (44.1%) with P = 0.0264. 2. After 6 weeks healing period, however, BIC percentage of calcium phosphate coated implants group (79.0%) was similar to the machined only implant group (78.6%). There was no statistical difference between two groups (P = 0.8074). 3. We found the significant deference between the control group and experimental group during the early healing period of 3 weeks. But no statistical difference was found between two groups during the later of 6 weeks.

• International Journal of Precision Engineering and Manufacturing
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• v.9 no.4
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• pp.74-78
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• 2008

High-speed tool steels are extensively used in tooling industries for manufacturing cutting tools, forming tools, and rolls. Electrical discharge machining (EDM) has been found to be an effective process for machining these extremely hard and difficult-to-cut materials. Extensive research has been conducted to identify the optimum machining parameters for EDM with different tool steels. This paper presents a fundamental study of the surface characteristics of SKH-51 tool steel machined by micro-EDM, with particular focus on obtaining a better surface finish. An RC pulse generator was used to obtain a better surface finish as it produces fine discharge craters. The main operating parameters studied were the gap voltage and the capacitance while the resistance and other gap control parameters were kept constant. A negative tungsten electrode was used in this study. The micro-EDM performance was analyzed by atomic force microscopy to determine the average surface roughness and the distance between the highest peak and lowest valley. The topography of the machined surface was observed using a scanning electron microscope and a digital optical microscope.

• Journal of the Korean Society for Precision Engineering
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• v.21 no.4
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• pp.24-31
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• 2004

The objective of this work is to suggest a mastless pattern fabrication technique using the combination of machining by Nanoindenter(equation omitted) XP and HF wet etching. Sample line patterns were machined on a borosilicate surface by constant load scratch (CLS) of the Nanoindenter(equation omitted) XP with a Berkovich diamond tip, and they were etched in HF solution to investigate chemical characteristics of the machined borosilicate surface. All morphological data of scratch traces were scanned using atomic force microscope (AFM).

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1997.04a
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• pp.873-877
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• 1997

This paper presents experimental results to know the charcteristics of machined surface due to cutter runout. Cutter runout is a common but undesirable phenomenon in multi-tooth machining such as end-milling process because it introduces variable chip loading to insert which results in a accelerated tool wear, amplification of force variation and hence enargement vibration amplitude. To develop in-proess cutter runout compensation system, set-up the micro-positoning mechanism which is based on piezoelectric translator embeded in the work holder to manipulate the depth of cut in real-time. And feasibility test of system was done under the various experimental cutting conditions. This results provide lots of information to build-up the precision machining technology.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2006.05a
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• pp.11-12
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• 2006

Actuator arm of HDD were machined with the slitting saw of tungsten carbide to clarify the cutting characteristics in terms of the roughness of machined surface, the burr size and the tool wear. An improved performance in all view of the surface machined, the tool life and the cutting efficiency was obtained at the cutting speed of 4,000rpm with the feed of 300m/min. The tool life increases with increasing the t/T value, whereas surface roughness decreases. The tool with alternate type of B and C edges has an effect to decrease the burr size.

• Journal of Periodontal and Implant Science
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• v.38 no.3
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• pp.467-474
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• 2008

Purpose: To evaluate RBM surface implant which has its good character like that good initial stability, early bone formation. Material and Methods: In this study fixures have divided in 2 group: Machined(Group I), RBM(Group II). Total 10 fixtures were implanted on rabbit which sacrificed on week 2 and week 4 for the histological specimens. By these specimens polarized microscopic view, micro CT view, ISQ value were measured, compared and analysed by each group to figure out the evidence that clinical use of RBM implant. Result: ISQ value had no significance differences between 2 groups, However in each group 4, 8 weeks had higher ISQ value than 2 weeks. In polarized microscope, calcification level was following: Group II, Group I. In micro CT, formation of cancellous bone level was following: Group II, Group I. Conclusion: RBM implant was the most excellent on the early bone formation and good initial stability.