• 한국윤활학회:학술대회논문집
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• 한국윤활학회 2003년도 학술대회지
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• pp.388-394
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• 2003

This paper deals with a premature failure mechanism of deep grooved ball bearing for automobiles. A close examination of used bearings revealed that the premature failure could be arose by dents on the ball. Universal testing machine with specially designed tools is used to simulate the practical dents on the ball and test bearings are assembled with dented balls and new hearing components. The endurance test results showed that the dents on the balls were printed on the races and these phenomena come to premature failure.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2007년도 제38회 하계학술대회
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• pp.1581-1582
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• 2007

본 컨트롤러는 기존 고속인쇄기 인쇄 속도인 250 [mpm]의 두 배 속도인 500 [mpm]의 고속 인쇄에서도 사용할 수 있는 고성능 레지스터 컨트롤러를 개발해 오차 보정을 좀 더 정확하고 신속하게 하는 것에 그 목적이 있다. 즉, 고속 인쇄기에서 인쇄물의 인쇄오차 보상을 위한 고속 인쇄기용 레지스터 컨트롤러의 특성을 분석하고, 고성능 DSP를 이용하여 기존의 하드웨어에 의존하던 기능의 상당 부분을 소프트웨어로 처리함으로써 간단한 하드웨어 구조와 고성능 오차 보상 기능을 갖는 레지스터 컨트롤러를 개발하였다.

• Journal of the Korean Association of Oral and Maxillofacial Surgeons
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• 제47권3호
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• pp.233-236
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• 2021

A mandibular continuity defect can be repaired using either a prosthetic device or autogenous bone. A titanium reconstruction plate can be used with a localized or vascularized flap over the defect of the mandible. Unfortunately, the plate may fail due to plate exposure, screw loosening, fracture, or infection, and will need to be removed. Plate exposure though the skin or mucosa is one of the main reasons for failure. In the present work, the authors introduced a lingually positioned reconstruction plate fabricated via three-dimensional printed bending support. This custom reconstruction plate can avoid plate re-exposure as well as reduce surgical errors and operation time.

• Journal of International Society for Simulation Surgery
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• 제1권1호
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• pp.13-15
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• 2014

Nowadays, with advanced 3D printing techniques, the custom-made implant can be manufactured for the patient. Especially in skull reconstruction, it is difficult to design the implant due to complicated geometry. In large defect, an autograft is inappropriate to cover the defect due to donor morbidity. We present the process of manufacturing the 3D custom-made implant for skull reconstruction. There was one patient with skull defect repaired using custom-made 3D titanium implant in the plastic and reconstructive surgery department. The patient had defect of the left parieto-temporal area after craniectomy due to traumatic subdural hematoma. Custom-made 3D titanium implants were manufactured by Medyssey Co., Ltd. using 3D CT data, Mimics software and an EBM (Electron Beam Melting) machine. The engineer and surgeon reviewed several different designs and simulated a mock surgery on 3D skull model. During the operation, the custom-made implant was fit to the defect properly without dead space. The operative site healed without any specific complications. In skull reconstruction, autograft has been the treatment of choice. However, it is not always available and depends on the size of defect and donor morbidity. As 3D printing technique has been advanced, it is useful to manufacture custom-made implant for skull reconstruction.

• The Journal of Advanced Prosthodontics
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• 제12권5호
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• pp.322-328
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• 2020

PURPOSE. This study evaluated the shear bond strength between 3D printed provisional resin and conventional provisional resin depending on type of conventional provisional resin and different surface treatments of 3D printed resin. MATERIALS AND METHODS. Ninety-six disc-shaped specimens (Ø14 mm × 20 mm thickness) were printed with resin for 3D printing (Nextdent C&B, Vertex-Dental B. V., Soesterberg, Netherlands). After post-processing, the specimens were randomly divided into 8 groups (n=12) according to two types of conventional repair resin (methylmethacrylate and bis-acryl composite) and four different surface treatments: no additional treatment, air abrasion, soaking in methylmethacrylate (MMA) monomer, and soaking in MMA monomer after air abrasion. After surface treatment, each repair resin was bonded in cylindrical shape using a silicone mold. Specimens were stored in 37℃ distilled water for 24 hours. The shear bond strength was measured using a universal testing machine at a crosshead speed of 0.5 mm/min. Failure modes were analyzed by scanning electron microscope. Statistical analysis was done using one-way ANOVA test and Kruskal-Wallis test (α=.05). RESULTS. The group repaired with bis-acryl composite without additional surface treatment showed the highest mean shear bond strength. It was significantly higher than all four groups repaired with methylmethacrylate (P<.05). Additional surface treatments, neither mechanical nor chemical, increased the shear bond strength within methylmethacrylate groups and bis-acryl composite groups (P>.05). Failure mode analysis showed that cohesive failure was most frequent in both methylmethacrylate and bis-acryl composite groups. CONCLUSION. Our results suggest that when repairing 3D printed provisional restoration with conventional provisional resin, repair with bis-acryl composite without additional surface treatment is recommended.

• The Journal of Advanced Prosthodontics
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• 제12권4호
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• pp.218-224
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• 2020

PURPOSE. The objectives of this study were to evaluate the fracture strength and fracture patterns of provisional crowns fabricated from different materials and techniques after receiving stress from a simulated oral condition. MATERIALS AND METHODS. A monomethacrylate-based resin (Unifast Trad) and a bis-acryl-based (Protemp 4) resin were used to fabricate provisional crowns using conventional direct technique. A milled monomethacrylate resin (Brylic Solid) and a 3D-printed bis-acrylate resin (Freeprint Temp) were chosen to fabricate provisional crowns using the CAD/CAM process. All cemented provisional crowns (n=10/group) were subjected to thermal cycling (5,000 cycles at 5°-55℃) and cyclic occlusal load (100 N at 4 Hz for 100,000 cycles). Maximum force at fracture was tested using a universal testing machine. RESULTS. Maximum force at fracture (mean ± SD, N) of each group was 657.87 ± 82.84 for Unifast Trad, 1125.94 ± 168.07 for Protemp4, 953.60 ± 58.88 for Brylic Solid, and 1004.19 ± 122.18 for Freeprint Temp. One-way ANOVA with Tamhane post hoc test showed that the fracture strength of Unifast Trad was statistically significantly lower than others (P<.01). No statistically significant difference was noted among other groups. For failure pattern analysis, Unifast Trad and Brylic Solid showed less damage than Protemp 4 and Freeprint Temp groups. CONCLUSION. Provisional crowns fabricated using the CAD/CAM process and the conventionally fabricated bis-acryl resins exhibited significant higher fracture strength compared to conventionally fabricated monomethacrylate resins after the aging regimen. Therefore, CAD/CAM milling and 3D printing of provisional restorations may be good alternatives for long term provisionalization.

• 한국전자통신학회논문지
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• 제15권4호
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• pp.759-764
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• 2020

4차 산업혁명에 맞춰 제조·생산의 패러다임 또한 변경되고 있는 상황에서 인더스트리 4.0에 대한 사회적 요구 및 방향은 이미 되돌릴 수 없으며, 그로 인하여 3D프린팅 기술의 확장성과 범용성이 주목받고 있다. 3D 프린터는 제품 개발 비용 감소를 위한 목적으로 개발된 기술로, 최근 3D 프린터 기술특허가 만료되면서 관련 기술이 공개되었고 이를 적용한 다양한 기술이 연구 개발되고 있으며 이로 인해 다양한 특이점이 발견 및 보완되고 있다. 이에 본 연구에서는 3D 프린터 사용에 있어 오프라인에서 기계를 직접 조정하고, 모델링 데이터의 직접 입력을 통해 3D프린팅 시작해야 하는 현재 출력방식에 대한 불편함을 보완하기 위해 다중 3D 프린터에 대한 실시간 온라인 출력요청 및 정상적인 출력물을 기대할 수 있는 모니터링 기능 그리고 다중 3D 프린터에 대한 온라인 실시간 원격관리 기능을 수행하기 위해 IoT 시스템에 대한 설계를 제안한다.

• 대한두개안면성형외과학회지
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• 제16권1호
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• pp.11-16
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• 2015

Background: Source material used to fill calvarial defects includes autologous bones and synthetic alternatives. While autologous bone is preferable to synthetic material, autologous reconstruction is not always feasible due to defect size, unacceptable donor-site morbidity, and other issues. Today, advanced three-dimensional (3D) printing techniques allow for fabrication of titanium implants customized to the exact need of individual patients with calvarial defects. In this report, we present three cases of calvarial reconstructions using 3D-printed porous titanium implants. Methods: From 2013 through 2014, three calvarial defects were repaired using custom-made 3D porous titanium implants. The defects were due either to traumatic subdural hematoma or to meningioma and were located in parieto-occipital, fronto-temporo-parietal, and parieto-temporal areas. The implants were prepared using individual 3D computed tomography (CT) data, Mimics software, and an electron beam melting machine. For each patient, several designs of the implant were evaluated against 3D-printed skull models. All three cases had a custom-made 3D porous titanium implant laid on the defect and rigid fixation was done with 8 mm screws. Results: The custom-made 3D implants fit each patient's skull defect precisely without any dead space. The operative site healed without any specific complications. Postoperative CTs revealed the implants to be in correct position. Conclusion: An autologous graft is not a feasible option in the reconstruction of large calvarial defects. Ideally, synthetic materials for calvarial reconstruction should be easily applicable, durable, and strong. In these aspects, a 3D titanium implant can be an optimal source material in calvarial reconstruction.

• 에너지공학
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• 제28권1호
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• pp.49-56
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• 2019

본 연구에서는 발전소에서 사용되는 부품의 넓은 표면을 세정하기 위한 브라스팅 노즐을 비압축성 유동해석에 기초하여 설계하였다. 설계된 노즐의 출구측 단면은 광폭의 직선 모양이다. 설계 후 3차원 프린팅으로 노즐 시제품을 제작하였고 이를 브라스팅 머신에 장착 후 세정 성능실험을 수행하였다. 해석 후 얻은 광폭 크기와 실험 후 시편 표면에서 얻은 세정된 광폭 크기가 거의 같았다. 이로부터 대면적 표면처리를 위한 브라스팅 노즐의 설계가 유효함을 확인하였다.

• 월간산업보건
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• 통권8호
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• pp.4-30
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• 1988

Examination of working environments was conducted to get more detailed data about harmful working environments and to make a contribution to more effective management. Study was carried out on 722 factories located in Taegu city and eight counties in Kyungpook Province, Korea, for a period of one year, from February 1 to December 30, 1986. The total number and proportion of workers exposed to harmful material was 37,697, 45.2% among 83,368 workers. The results according to exposed material were as follows: 1. In the case of noise, proportion of exceeding the 8-hour TLV was 59%, Included were nail-cutting in assembly metal manufacturing industry and weaving process in textile. 2. Dust in mill process of coal manufacturing industries exceeded the TLV of second class of dust at all parts and exceeded the TLV at 6% as a whole.: 3. The fields of industry lower than 70 lux of illumination were storage equipment of food, auto-winder of textile, painting of wood wares and coal mixing, and 44% of all cases was lower than standard. 4. As a result of temperature index investigation(WBGT), about 12% of all sujects exceeded limit value. Included parts were rolling machine and reducing room. 5. In the case of organic solvents, TLV was exceeded at about 8%, The parts exceeded TLV according to materials belonged to this category were as follows. 1) Toluene: adhesive work in assembly metal manufacturing 2) Xylene: printing and paint mixing in chemical manufacturing 3) Methyl ethytl ketone: paint mixing in all parts examined and coating machine partially in chemical manufacturing 4) Methyl isobutyl ketone: printing in chemical manufacturing 5) Acetone: vapor polishing in assembly metal manufacturing 6. Among specified chemical materials, the concentration of HC1 in the air in metal assembly manufacturing factory exceeded TLV. in one of three assembly metal manufacturing examined. Others, such as benzene, acetic acid, formic acid, sodium hydroxide, formalin, ammonia, copper, chromate etc. were lower than TLV in its indoor atmospheric concentration. As a whole, the proportion of exceeding TLV was about 0.8% 7. The concentrations of inorganic lead were lower than TLV in all parts examined. The results of this investigation show the fact that current management of working environments is not satisfactory, and so more active management is needed.