• Proceedings of the Korean Society of Precision Engineering Conference
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• 1995.10a
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• pp.105-108
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• 1995

So far,in deep drilling process there are several manufacturing problems such as hole deviation, hole over size, circularity,straightness and surface roughness. Whit regard to these problems, we atudied the abrasion process on carbided tip of BTA drill and got the follow test results through the abrasion characteristic test and analysis on cutting mechanism for the drill tooth and guide pad. 1) In SM55C drilling process, the most stable and reasonable drilling speed range for optmum abrasion characteristic of drill tooth was 60m.min. 2) The total drilling torque was about 60kg .deg.cm on condition drilling speed 60m/min and 0.15mm/rev. These results show that the theoretical burnising torque is well accord with the tested torque which is working on guide pad.

• The korean journal of orthodontics
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• v.19 no.2
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• pp.109-120
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• 1989

We tend to consider only static occlusion such as molar relationship, canine key, and interdigitation at finishing stage. Of course, this static occlusion is important for post-orthodontic stability. But we should remember that mandible is always on the move during its various functions. If no pressure or too much pressure is put on during its functions, untoward tooth movement could occur. And tooth mobility, periodontitis, wear facet, bruxism, and far worse temporomandibular disorder could occur. After many studies have been done on what is a desirable occlusal scheme to strengthen post-orthodontic stability, today, "mutually protective occlusion" is recommended. If an orthodontist does not have understanding about this occlusal scheme during orthodontic treatment, the following conditions will be resulted after orthodontic treatment. I. Centric discrepancy 1. centric prematurity 2. sunday bite 3. molar fulcrum II. Eccentric discrepancy 1. posterior interference 2. anterior interference If we have deep understanding about these discrepancies that can happen after orthodontic treatment and their causes, corrections, and especially preventions against them, post-orthodontic stability could be strengthened and further temporomandibular disorder could be prevented.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2000.11a
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• pp.801-805
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• 2000

This paper presents a new method of tool path optimization. A NC verification model based Z-map was utilized to obtain chip load in feed per tooth. This developed software can regenerate a NC program from cutting condition and the NC program that was generated in CAM. The regenerated NC program has not only all same data of the ex-NC program but also the new feed rates in every block. The new NC data can reduce the cutting time and manufacture precision dies with the same chip load in feed per tooth. This method can also prevent tool chipping and make constant tool wear. This paper considered the effects of acceleration and deceleration in feed rate change.

• 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.

• 한국금형공학회:학술대회논문집
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• 2008.06a
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• pp.129-133
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• 2008

As a rotating machine element, plastic gears are more and more widely used in such as industrial machine element, since plastic gear is lighter, higher wear-resistance, and higher vibration absorbing ability than metal gears. When operating plastic parts, tooth breakage and fatigue life shortened due to increasing number of applying load and tooth flank temperature rising, such that accuracy of plastic gears is divided from allowable range to cause vibration and noise. On this study, a internal plastic gears are developed which improved the filling balance molding process by a new injection mold structure. The new mold structure called HR3P(hot runner type 3plate mold). As the result from this studies, we obtained a very accurate roundness internal gears by using design of experiment.

• The Journal of Korean Academy of Prosthodontics
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• v.38 no.3
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• pp.366-374
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• 2000

FRC/ceromer system provides the clinician with a durable, flexible, and esthetic alternative to conventional porcelain fused to metal crowns. FRC is the matrix which is silica-coated and embedded in a resin matrix. The ceromer material which is a second generation indirect composite resin contains silanized, microhybrid inorganic fillers embedded in a light-curing organic matrix. FRC/ceromer restoration has a several advantages: better shock absorption, less wear of occluding teeth, translucency, color stability, bonding ability to dental hard tissues, and resiliency. It has versatility of use including inlay, onlay, single crown, and esthetic veneers. With adhesive technique, it can be used for single tooth replacement in forms of inlay adhesion bridge. In single tooth missing case, conventional PFM bridge has been used for esthetic restoration. However, this restoration has several disadvantages such as high cost, potential framework distortion during fabrication, and difficulty in repairing fractures. Inlay adhesion bridge with FRC/ceromer would be a good alternative treatment plan. This article describes a cases restored with Targis/Vectris inlay adhesion bridge. Tooth preparation guide, fabrication procedure, and cementation procedure of this system will be dealt. The strength/weakness of this restoration will be mentioned, also. If it has been used appropriately in carefully selected case, it can satisfy not only dentist's demand of sparing dental hard tissue but also patient's desire of seeking a esthetic restorations with a natural appearance.

• Journal of the Korean Society for Precision Engineering
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• v.18 no.5
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• pp.130-136
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• 2001

Generally, a metal slitting saw is plain milling cutter with thickness less than 3/16 inch. This is used for cutting a workpiece that high dimensional accuracy and surface finish is necessary. A small thin milling cutter like a metal slitting saw is useful for machining a narrow groove. In this case, built up edge(BUE) is severe at each tooth and affects the surface integrity of the machined surface and tool wear. It is well known that tool geometry and cutting conditions are decisive factors to remove BUE. In this paper, we optimized the geometry of the milling cutter and selected cutting conditions to remove BUE by the experimental investigation. The experiment was planned with Taguchi method based on the orthogonal array of design factors such as coating, rake angle, number of tooth, cutting speed, feed rate. Response table was obtained from the number of built-up edge generated at tooth. The optimized tool geometry and cutting conditions could be determined through response table. In addition, the relative effect of factors was identified bh the analysis of variance (ANOVA). Finally, coating and cutting speed turned out important factors for BUE.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.20 no.7
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• pp.677-684
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• 2010

Backlashes of gears provide gears for good lubrication and for removal of the interference between teeth by the wear and manufacturing errors. The backlash is the strong nonlinear factor to gears. This study deals with nonlinear modeling of helical gears with backlash. Excitation of helical gears comes from torque variation, the tooth surface error, and the periodical change of mesh stiffness. To study the effect of torque fluctuation, equation of motion for the single degree of freedom torsional model of helical gears with the periodical change of mesh stiffness and the backlash was derived. The Newmark beta method and the Newton-Raphson method were used to obtain the nonlinear behaviors of mesh forces of helical gears. All excitation frequencies initially caused the tooth separation and single-sided impacts of the gear pair and eventually led to the normal tooth contact. However, some special excitation frequencies caused the single-sided impacts in the entire time as well as the initial time. Damping increase reduced the duration of single-sided impacts, and the backlash increase caused those in the entire time domain.

• Korean Journal of Materials Research
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• v.14 no.1
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• pp.52-58
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• 2004

The surface property and formation behavior of a boride layer formed on Ni-Cr-Mo steel in a plasma paste boronizing treatment were investigated. The plasma paste boronizing treatment was carried out at 973～1273 K for 1-7 hrs under the gas ratio of Ar:H$_2$ (2:1). The thickness of the boride layer increased with increasing temperature and time in the boronizing treatment. The cross-section of the boride layer was a tooth structure and the hardness was Hv 2000～2500. XRD analysis revealed that the compound was identified as FeB, $Fe_2$B, and mixed phase of FeB/$Fe_2$B in the boride layer formed at 973～1073 K, 1173K, and 1273K, respectively. The Ni-Cr-Mo alloy boronized at 1173-1273 K showed the best excellent wear resistance against the sand. As a results of corrosion test in 1 M $H_2$$SO_4$ solution, $Fe_2$B formed on the matrix alloy exhibited higher corrosion resistance than FeB.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2002.11a
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• pp.363.1-363
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• 2002

This paper presents that the Wavelet Transform can be used to detect the various local defects in a gearbox. Two types of defects which are broken tooth and localized wear, are experimented and the signals are collected by accerometer and acoustic sensors and analyized. Because of the complecity of the signals acquired form sensors, it is needed to identify the interesting signal. (omitted)