• 마이크로전자및패키징학회지
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• 제25권1호
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• pp.23-28
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• 2018

최근 4차 산업혁명의 조류 하에 표면 실장 분야에서도 Smart Factory 구현을 위한 노력이 활발히 이루어지고 있다. 표면 실장 분야에서도 이러한 변화와 발 맞추어 많은 연구가 진행되고 있으며, 그중 핵심 공정이라 할 수 있는 솔더 인쇄 공정의 최적화에 대한 방법과 인쇄 효율에 영향을 미치는 인쇄 외적 요소에 대한 영향도를 분석하였다. 이 분석에는 설비에서 제공하는 Big Data를 활용하여 통계적 방법으로 접근하였고, 신뢰성 높은 결과와 함께 시뮬레이션을 통해 결과을 예측할 수 있는 가능성을 확인하였다. 이 연구가 실장 분야의 Smart Factory 구현에 조금이나마 기여가 되었으면 하는 바람이다.

• 한국기계가공학회지
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• 제16권3호
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• pp.1-8
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• 2017

Tool path generation is a part of process planning in 3D printing. This is done before actual printing by a computer rather than an AM machine. The mesh geometry of the 3D model is sliced layer-by-layer along the Z-axis and tool paths are generated from the sliced layers. Each 2-dimensional layer can have two types of printing paths: (i) shell and (ii) infill. Shell paths are made of offset loops. During shell generation, twists can be produced in offset loops which will cause twisted tool paths. As a twisted tool path cannot be printed, it is necessary to remove these twists during process planning. In this research, An algorithm is presented to remove twists from the offset loops. To do so the path segments are traversed to identify twisted points. Outer offset loops are represented in the counter-clockwise segment order and clockwise rotation for the inner offset loop to decide which twisted loop should be removed. After testing practical 3D models, the proposed algorithm is verified to use in tool path generation for 3D printing.

• 한국기계가공학회지
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• 제20권2호
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• pp.38-44
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• 2021

To cater to the transition from single-color to multicolor/multi-material printing, this paper proposes a cartridge-replacing type multi-nozzle Fused Depositon Modeling(FDM) three-dimensional (3D) printer. In the test printing run, tool change failure/wobble/layer shift occurred. It was confirmed that improper support was the cause of this tool change failure. As a solution, spline and electromagnetic cartridges were designed. Wobble was caused by machine vibration and the motor stepping out. To minimize wobble, an additional Z-axis was installed, and the four-point bed leveling method was used instead of the three-point bed leveling method. The occurrence of layer shift was ascribed to the eccentricity of the Z-axis lead screw. Therefore, slit coupler was replaced with an Oldham type. In addition to the mechanical supplementation, the control environment was integrated to prevent accidents and signal errors due to wire connections. Before the final test printing run, a rectifier circuit was added to the motor to secure precise control stability. The final test printing run confirmed that the wobble/layer shift phenomenon was minimized, and the maximum error between layers was reduced to 0.05.

• 한국기계가공학회지
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• 제14권4호
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• pp.62-72
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• 2015

Interest in three-dimensional (3D) printing processes has grown significantly, and several types have been developed. These 3D printing processes are classified as Selective Laser Sintering (SLS), Stereo-Lithography Apparatus (SLA), and Fused Deposition Modeling (FDM). SLS can be applied to many materials, but because it uses a laser-based material removal process, it is expensive. SLA enables fast and precise manufacturing, but available materials are limited. FDM printing's benefits are its reasonable price and easy accessibility. However, metal printing using FDM can involve technical problems, such as suitable component supply or the thermal expansion of the heating part. Thus, FDM printing primarily uses materials with low melting points, such as acrylonitrile butadiene styrene (ABS) or polylactic acid (PLA) resin. In this study, an FDM process for enabling metal printing is suggested. Particularly, the nozzle and heatsink for this process are focused for stable printing. To design the nozzle and heatsink, multi-physical phenomena, including thermal expansion and heat transfer, had to be considered. Therefore, COMSOL Multiphysics, an FEM analysis program, was used to analyze the maximum temperature, thermal expansion, and principal stress. Finally, its performance was confirmed through an experiment.

• The Journal of Advanced Prosthodontics
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• 제9권4호
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• pp.265-270
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• 2017

PURPOSE. This study is to evaluate the internal fit of the crown manufactured by CAD/CAM milling method and 3D printing method. MATERIALS AND METHODS. The master model was fabricated with stainless steel by using CNC machine and the work model was created from the vinyl-polysiloxane impression. After scanning the working model, the design software is used to design the crown. The saved STL file is used on the CAD/CAM milling method and two types of 3D printing method to produce 10 interim crowns per group. Internal discrepancy measurement uses the silicon replica method and the measured data are analyzed with One-way ANOVA to verify the statistic significance. RESULTS. The discrepancy means (standard deviation) of the 3 groups are $171.6\;(97.4){\mu}m$ for the crown manufactured by the milling system and 149.1 (65.9) and $91.1\;(36.4){\mu}m$, respectively, for the crowns manufactured with the two types of 3D printing system. There was a statistically significant difference and the 3D printing system group showed more outstanding value than the milling system group. CONCLUSION. The marginal and internal fit of the interim restoration has more outstanding 3D printing method than the CAD/CAM milling method. Therefore, the 3D printing method is considered as applicable for not only the interim restoration production, but also in the dental prosthesis production with a higher level of completion.

• 한국염색가공학회지
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• 제22권3호
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• pp.282-291
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• 2010

Digital textile printing(DTP) is becoming more important because the production trend of textile printing goods is adapting to small-lot multiple items. Recently enhanced use of DTP is closely connected with production of high value-added products in fashion industry, which is also appropriate for quick response system(QRS). Quality of DTP depends on pre-treatment, after-treatment, ink, media, printer, etc. One of these parameters, Selection of good media is very important to obtain high quality of DTP products. Especially, the effects of media on printing quality of DTP according to yarn twist and structure of knitting fabric were examined in this study. Two types of yarn twist of 830 t.p.m and 1630 t.p.m for cotton knit were used and five types of media structures were knitted with single circular knitting machine. First, MIU, MMD, SMD's values are closely related with surface roughness of sample as well as printing quality. The hard twist samples were higher values than normal twist samples in the same media structure. In case of SMD, the values increased from plain to corduroy types. Second, aspect of line sharpness, line area, and line width values of hard twist samples decreased from plain to corduroy than those of normal twist samples. Third, line deviation values of hard twist samples, blurriness of line, also decreased than those of normal twist samples.

• 구강회복응용과학지
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• 제37권1호
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• pp.16-22
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• 2021

목적: 표면연마와 제작방법이 임시 수복용 레진의 굽힘강도에 미치는 영향을 분석하고자 한다. 연구 재료 및 방법: 4가지 제작방법을 이용하여 각각 30개의 임시 수복용 레진 시편을 제작하였고, 기계적 연마로 표면연마를 시행한 그룹과 연마를 시행하지 않은 2개의 그룹으로 나누었다. 시편은 37℃ 항온기에 24시간 보관 후 만능시험기(Universal testing machine)을 이용하여 3점 굽힘강도를 측정하였다. 통계분석은 Two-way ANOVA와 Tukey's HSD test, Paired t-test를 이용하여 분석하였다. 결과: 표면연마 여부와 관계없이 CAD/CAM milling으로 제작한 시편이 가장 높은 굽힘강도를 나타냈고, SLA 3D printing, DLP 3D printing, Conventional method 순으로 높은 굽힘강도를 나타냈다. 결론: 표면연마는 임시 수복용 레진의 굽힘강도에 유의한 영향을 끼치지 못했지만(P > 0.05), 제작방법에 의해서는 굽힘강도의 유의한 차이가 나타났다(P < 0.05).

• 한국기계가공학회지
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• 제18권7호
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• pp.83-89
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• 2019

In the conventional casting and forging method, there is a disadvantage that a mold is an essential addition, and a production cost is increased when a small quantity is produced. In order to overcome this disadvantage, a metal 3D printing production method capable of directly forming a shape without a mold frame is mainly used. In particular, overseas research has been conducted on various materials, one of which is a metal printer. Similarly, domestic companies are also concentrating on the metal printer market. However, In this case of the conventional metal 3D printing method, it is difficult to meet the needs of the industry because of the high cost of materials, equipment and maintenance for product strength and production. To compensate for these weaknesses, printers have been developed that can be manufactured using sand mold, but they are not accessible to the printer company and are expensive to machine. Therefore, it is necessary to supply three-dimensional casting printers capable of metal molding by producing molds instead of conventional metal 3D printing methods. In this study, we intend to reduce the unit price by replacing the printing method used in the sand casting printer with the FDM method. In addition, Ag paste is used to design the output conditions and enable ceramic printing.

• 펄프종이기술
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• 제32권2호
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• pp.51-57
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• 2000

Cylinder machine usually gives more fiber orientation than fourdrinier and has limitation in machine speed because of fiber wash-off caused by centrifugal force when machine speed increases. This study aimed for the improvement of paper formation and productivity by setting an apron in vat inlet and by adjusting mould water head. Improvement of formation and increase of machine speed were achieved, which ultimately improve productivity. Installing an apron successfully decreased fiber wash-off. Fiber orientation and two-sideness of ash distribution became less severe. The proper adjustment of water head inside the cylinder mould proved to be an important factor not only in paper formation but also in decreasing paper two-sideness.

• 한국정보디스플레이학회:학술대회논문집
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• 한국정보디스플레이학회 2008년도 International Meeting on Information Display
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• pp.1638-1641
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• 2008

We have investigated the effectiveness of a gravure printing method for the fabrication of organic light-emitting diode (OLED) and Organic Thin Film Transistor (OTFT). Printing of the organic layers was performed with a small-scale gravure coating machine, while the metallic layers were vacuum-evaporated. Devices with gravure-printed layers are at least comparable with the spin-coated devices. Effects of the solvent formulation and surface energy mismatch between the organic layer materials on the printed patterns and device performance were discussed. We will present the initial design and experimental data of OTFT fabricated by roll-type soft contact transfer process.