• 제목/요약/키워드: Internal Grinding

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마이크로 코어 핀 정밀 연삭 시스템 (Precision Grinding System for Micro Core-pin)

  • 양지경;이인철;강동성;한봉석;한유진;이정우;송기혁
    • 한국산학기술학회논문지
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    • 제18권4호
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    • pp.50-57
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    • 2017
  • 본 사출 금형을 통해 제품 생산 시 사출 금형 내에서 제품 형상을 형성하는 코어는 금형 내부에 틀의 형태로 가공되어 설치되며 이때 부분적인 코어의 형상을 핀에 가공하여 설치하는 부품을 코어 핀이라 한다. 이러한 사출 코어 용 코어 핀은 제품의 소형화 집적화에 따라 그 크기가 마이크로의 크기로 작아지고 있다. 하지만 이를 가공 시 기존의 센터리스 연삭 장치로는 마이크로 사이즈의 피삭재를 고정하여 밀착 시켜주는 장치의 부재로 인해 진동이 발생한다. 이러한 이유로 마이크로 크기의 직경을 가지는 코어 핀의 경우 가공 시 진동에 의해 변형 발생으로 가공 불량률이 매우 높다. 따라서 본 논문에서는 마이크로 크기의 코어 핀을 가공하기 위해 기존의 평면 연삭기에 설치하여 사용이 가능한 소형의 연삭 시스템을 개발 하였다. 이를 이용하여 코어 핀에 대한 연삭 실험을 진행하였으며 표면 거칠기, 진원도, 원통도의 측정을 통해 성능을 검증하였다.

교합 및 외과적 치료를 이용한 악관적 내장증의 치험례 (Surgical and Occlusal Treatment of TMJ Internal Derangement)

  • 황경룡;안재진;장세홍
    • 대한치과의사협회지
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    • 제25권7호통권218호
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    • pp.657-664
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    • 1987
  • The purpose of this article is to report a case of internal derangement of TMJ which was successfully managed with surgical and occlusal treatment. The Obtained results were summarized as follow: 1. The patient surgically operated via high condylectomy with meniscoplasty to correct anteriorly displaced meniscus. 2. During operation, the junction area of bilamina zone and meniscus was easily identified and resected using microscopy. 3. The mandible was relocated into therapeutic position with occlusal splint. 4. The occlusal rehabilitation with selective grinding and prosthodontic treatment was done so that the new patient's intercuspal position should correspond to the therapeutic position.

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누적통과톤수에 의한 레일교체기준의 타당성 분석 (A Study on Logicality for the Periodic Replacements of Continuous Welded Rail based on Accumulated Passing Tonnage)

  • 성덕룡;공선용;김박진;신효정;박용걸
    • 한국철도학회:학술대회논문집
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    • 한국철도학회 2007년도 추계학술대회 논문집
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    • pp.1058-1070
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    • 2007
  • Internal and external railway management corporations are using the periodic replacement criteria of rail by accumulated passing tonnage and wear to maintain rails for servicing. However, internal the periodic replacement criteria of continuous welded rail(CWR) by accumulated passing tonnage is the one(50kg/m-5 million gross tonnage, 60kg/m-6 million gross tonnage) presented in Japan before. It was estimated with the fatigue life about 50kg N rail joints applied diesel train load but it wasn't applied to current conditions of track; elimination of rail joint, using the concrete slab track and operation of light train load and effect of welding, manufacturing technique, grinding of rail. Therefore, in this study, it was investigated the types of damage and cause in welded rails and examined standards and information resources. Also, this study presents preliminary data to revise the periodic replacement criteria of CWR by current accumulated passing tonnage in bending test of laid welded rail and a survey of track maintenance history of Seoul metro.

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금 합금 보철물의 교합면 삭제로 인한 임플란트-골 계면으로의 열전달에 관한 연구 (Study of heat transfer to the implant-bone interface induced by grinding of occlusal surface of implant gold prosthesis)

  • 조재영;강선녀;정창모;윤미정;허중보;전영찬
    • 대한치과보철학회지
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    • 제50권1호
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    • pp.29-35
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    • 2012
  • 연구 목적: 임플란트-골 계면에서 발생하는 과도한 열은 골유착을 저해하여 임플란트의 실패를 유발한다. 이에 이번 연구에서는 임플란트 금 합금 보철물의 교합면 삭제시 임플란트-골 계면으로의 열전달 양상과 냉각 방식의 효율성을 알아 보고자 하였다. 연구 재료 및 방법: 온도 감지 장치 제작을 위하여 Internal cone 연결형태의 임플란트에 16개의 K형 열전대를 부착하여 아크릴릭 레진에 포매하였다. 치과용 금 합금과 주조용 abutment를 사용하여 교합면에 3개의 요철을 가지는 시편을 10개 제작하였고, 연결 나사를 이용하여 임플란트와 연결한 뒤 온도 감지 장치를 $37^{\circ}C$ 유지되는 수조에 위치시켰다. 저속 핸드피스와 green stone bur를 이용하여 30초 동안 보철물의 요철을 삭제하였는데, 무냉각군, 공기 냉각 군, 물 분사 냉각 군으로 나누어 요철을 삭제하였다. 보철물이 삭제 되는 동안 임플란트의 부위별로 온도가 0.05초 간격으로 기록되었고, 삭제를 멈춘 뒤에도 무 냉각 군의 경우 임계 온도인 $47^{\circ}C$ 이하로 온도가 하강할 때까지, 공기 냉각군과 물 분사 냉각군의 경우 삭제 중단 후 30초 동안 추가로 온도를 기록하였다. 냉각 방식에 따른 임플란트-골 계면의 온도를 알아보고, 임플란트의 부위별 온도변화의 유의차를 알아보기 위하여 one-way ANOVA를 실시하였고, Turkey HSD 이용하여 95% 유의수준에서 사후 검증하였다. 결과: 무 냉각 군은 임플란트-골 계면의 온도가 $47^{\circ}C$ 이상으로 상승하였으며, 임플란트의 경부에서 유의하게 높은 열이 측정되었다(P>.05). 공기냉각군과물분사냉각군은 임플란트-골 계면의 온도가 $47^{\circ}C$ 이하로 유지되었다. 무 냉각 군에서 임플란트 경부의 온도가 $47^{\circ}C$에 도달되는 데는 약 $10.8{\pm}1.5$초가 소요되었다. 공기 냉각 군과 물 분사 냉각 군 사이에서는 임플란트-골 계면 온도의 유의차가 없었다(P>.05). 결론: 이상의 결과로부터 임플란트 금 합금 보철물의 교합면 삭제 시, 임플란트 주위 조직에 위해를 가할 수 있는 임계 온도 이상의 열이 발생했음을 알 수 있었으며, 냉각 방식은 공기 냉각과 물 분사 냉각 모두 효과적이라고 생각된다.

고강성 병렬형 로봇의 최적 여유 구동 (Optimal Redundant Actuation of Parallel Manipulators with High Operational Stiffness)

  • 김성복
    • 제어로봇시스템학회논문지
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    • 제6권2호
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    • pp.181-189
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    • 2000
  • This paper presents the optimal redundant actuation of parallel manipulators for complicated robotic applications such as cutting grinding drilling and digging that require a high degree of operational stiffness as well as the balance between force applicability and dexterity. First by taking into account the distribution(number and location) of active joints the statics and the operational stiffness of a redundant parallel manipulator are formulated and the effects of actuation redundancy are analyzed, Second for given task requirements including joint torque limit task force maximum allowable disturbance and maximum allowable deflection the task execution conditions of a redundant parallel manipulator are derived and the efficient testing formulas are provided. Third to achieve high operational stiffness while maintaining moderate dexterity the redundant actuation of a parallel manipulator is optimized which determines the optimal distribution of active joints and the optimal internal joint torque, Finally the simulation results for the optimal redundant actuation of a planar parallel manipulator are given.

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베어링의 로브형상과 절삭력 모델링 (Bearing Lobe Profile and Cutting Force Modeling)

  • 윤문철;조현덕;김성근
    • 한국윤활학회:학술대회논문집
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    • 한국윤활학회 1998년도 제28회 추계학술대회
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    • pp.343-349
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    • 1998
  • A modeling of machined geometry and cutting force was proposed for the case of round shape machining, and the effects of internally machined profile are analyzed and its realiability was verified by the experiments of roundness tester, especially in boring operation in lathe. Also, harmonic cutting force model was proposed with the parameter of specific cutting force, chip width and chip thickness, and in this study, we can see that bored workpiece profile was also mapped into cutting force signal with this model. In general, we can calculated the theoretical lobe profile with arbitrary multilobe. But in real experiments, the most frequently measured numbers are 3 and 5 lobe profile in experiments. With this results, we can predict that these results may be applied to round shape machining such as drilling, boring, ball screw and internal grinding operation with the same method.

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고속태핑에 있어서 탭의 형상과 절삭토크의 특성 (On Tap Geometry and Characteristics of Torque in High Speed Tapping)

  • 최만성;송지복
    • 한국정밀공학회지
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    • 제13권8호
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    • pp.139-145
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    • 1996
  • Tapping is one of the most widely used machining operations. There are several methodes of producing external screw threads, e.g. turning, milling with single or multiple cutter, rolling, and grinding, but the methods available for cutting enternal threads are less numerous, and for threads in small holes, tapping is employed almost exclusively. In this study, the tap with the various geometry has been developed in order to tap special workmaterial at considerably higher cutting speed than that of the conventional HSS tap. The experimental tests are run with various cutting speed by using a piezo type tool dynamometer to measure tapping torque. Tapping torque is affected by the design of the tap, which seems to be due to internal friction and shearing of the metal. It is clarified that the process of chip formation strongly depends on rake angle, relief angle, angle of twist.

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복합레진 인레이 수복시 와동형태에 따른 치아파절에 관한 유한요소법적 연구 (A THREE DIMENSIONAL FINITE ELEMENT ANALYSIS WITH CAVITY DESIGN ON FRACTURE OF COMPOSITE RESIN INLAY RESTORED TOOTH)

  • 김철순;민병순
    • Restorative Dentistry and Endodontics
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    • 제19권1호
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    • pp.231-254
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    • 1994
  • Fracture of cusp, on posterior teeth, especially those carious or restored, is major cause of tooth loss. Inappropriate treatments, such as unnecessarily wide cavity preparations, increase the potential of further trauma and possible fracture of the remaining tooth structures. Fracture potential may be directly related to the stresses exerted upon the tooth during masticatory function. The purpose of this study is to evaluate the fracture resistance of tooth, restored with composite resin inlay. In this study, MOD inlay cavity prepared on maxillary first premolar and restored with composite resin inlay. Three dimensional finite element models with eight nodes isoparametric solid element, developed by serial grinding-photographing technique. These models have various occlusal isthmus and depth of cavity, 1/2, 1/3 and 1/4 of isthmus width and 0.7, 0.85 and 1.0 of depth of cavity. The magnitude of load was 474 N and 172 N as presented to maximal biting force and normal chewing force. These loads applied onto ridges of buccal and lingual cusp. These models analyzed with three dimensional finite element method. The results of this study were as follows : 1. There is no difference of displacement between width of occlusal isthmus and depth of cavity. 2. The stress concentrated at bucco-mesial comer, bucco-disal comer, pulpal line angle and the interface area between internal slopes of cusp and resin inlay. 3. The vector of stress direct to buccal and lingual side from center of cavity, to tooth surface going on to enamel. The magnitude of vector increase from occlusal surface to cervix. 4. The crack of tooth start interface area, between internal slop of buccal cusp and resin inlay. It progresses through buccopulpal line angle to cervix at buccomesial and buccodistal comer. 5. The influence with depth of cavity to fracture of tooth was more than width of isthmus. 6. It would be favorable to make the isthmus width narrower than a third of the intercuspal distance and depth of cavity is below 1 : 0.7.

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500 MW 석탄화력 발전소에서 바이오매스 혼소율이 미분기 운전인자에 미치는 영향 (Effect of Biomass Co-firing Ratio on Operating Factors of Pulverizer in 500 MW Coal-fired Power Plant)

  • 금준호;문승재
    • 플랜트 저널
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    • 제18권3호
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    • pp.28-40
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    • 2022
  • 신재생에너지 발전 비중 확대가 예상됨에 따라 공공 발전사업자들은 바이오매스 혼소의 확대 시행을 적극적으로 검토해야 할 필요가 있다. 본 연구에서는 500MW 석탄화력에서 바이오매스 혼소율을 0wt.%에서 5.0wt.%까지 변화하며 미분기 주요 운전 특성을 측정하였다. 먼저, 목질계 바이오매스에 대한 구성성분 분석과 분쇄 특성을 알아보았고, 혼합연료의 부피 증가가 미분기 보울 압력 차이, 모터 전류, 이물질 처리횟수, 출구 온도, 내부 화재횟수에 미치는 영향을 분석하였다. 혼소율 증가에 따라 미분기 보울 압력 차이와 모터 전류, 이물질 처리횟수는 상승함을 확인하였고, 출구 온도는 상승 폭이 미미하였다. 내부 화재횟수는 명확한 상관관계를 찾기 힘드나, 다른 운전인자와 결합하여 발생할 가능성이 크다는 것을 확인하였다.

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Direct Detection of Cylindrocarpon destructans, Root Rot Pathogen of Ginseng by Nested PCR from Soil Samples

  • Jang, Chang-Soon;Lim, Jin-Ha;Seo, Mun-Won;Song, Jeong-Young;Kim, Hong-Gi
    • Mycobiology
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    • 제38권1호
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    • pp.33-38
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    • 2010
  • We have successfully applied the nested PCR to detect Cylindrocarpon destructans, a major pathogen causing root rot disease from ginseng seedlings in our former study. The PCR assay, in this study, was used to detect the pathogen from soils. The nested PCR using internal transcribed spacer (ITS) 1, 4 primer set and Dest 1, 4 primer set maintained the specificity in soils containing various microorganisms. For a soil DNA extraction method targeting chlamydospores, when several cell wall disrupting methods were tested, the combination of lyophilization and grinding with glass beads, which broke almost all the chlamydospores, was the strongest. The DNA extraction method which was completed based on the above was simple and time-saving because of exclusion of unnecessary stages, and efficient to apply in soils. As three ginseng fields whose histories were known were analyzed, the PCR assay resulted as our expectation derived from the field information. The direct PCR method will be utilized as a reliable and rapid tool for detecting and monitoring C. destructans in ginseng fields.