• Journal of the Korean Society of Manufacturing Process Engineers
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• v.19 no.1
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• pp.81-88
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• 2020

In this paper, the performances of the electrical characteristics of the Fused Deposition Modeling (FDM) 3D-printed flexible resistance sensor was evaluated. The FDM 3D printing flexible resistive sensor is composed of flexible-material thermoplastic polyurethane and a conductive PLA (carbon black conductive polylactic acid) polymer. While 3D printing, polymer filaments heat up quickly before being extruded and cooled down quickly. Polymers have poor thermal conductivity so the heating and cooling causes unevenness, which then results in internal stress on the printed parts due to the rapidity of the heating and cooling. Electrical resistance measurements show that the 3D-printed flexible sensor is unstable due to internal stress, so the 3D-printed flexible sensor resistance curve does not match the increases and decreases in the displacement curve. Therefore, annealing was performed to eliminate the mismatch between electrical resistance and displacement. Annealing eliminates residual stress on the sensor, so the electrical resistance of the sensor increases and decreases in proportion to displacement. Additionally, the resistance is lowered in comparison to before annealing. The results of this study will be very useful for the fabrication of various devices that employ 3D-printed flexible sensor that have multiple degrees of freedom and are not limited by size and shape.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 1998.06b
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• pp.1-7
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• 1998

본 연구에서는 3차원 솔리드 모델러로부터 Modeling한 후 제작된 model 에 사용자가 원하는 측정 위치를 지정함으로써 자동적으로 측정용 NC Data를 얻을 수 있는 알고리즘을 설계하고 이를 Program화하였다. 3-D Modeler로서 Unigraphics를 사용하였으며, 공작기계는 FANUC Controller를 장착한 Machining Center이다. 측정용 센서는 접촉식 Probe를 사용하였다. 본 연구를 통하여 CAD시스템에서 구축된 Geomaatric Model로부터 직접 측정을 위한 NC data를 얻고 이 data를 가공후의 측정 Data와 비교하여 봄으로써 제품의 가공정밀도를 확인해 볼 수 있으며, 가공시의 간섭 check, 잔삭가공여유, 과절삭등 다양한 정보를 얻을 수 있을 것이다. 향수 지속적인 연구개발을 통하여 data의 통계처리 및 공작기계의 오차 보정등을 고려하여 줌으로써 기계상에서의 측정 data에 대한 신뢰도를 구축할 수 있을 것으로 사료된다.

• The Journal of Korean Academy of Prosthodontics
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• v.58 no.4
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• pp.313-320
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• 2020

Purpose: The purpose of this study was to evaluate the machining precision and the marginal and internal fit of single restorations fabricated with three types of lithium disilicate ceramic blocks and to evaluate the correlation. Materials and methods: Single restorations were designed using a CAD software program. The crown designed model file was extracted from the CAD software program. Three types of lithium disilicate blocks (Rosetta; HASS, IPS e.max CAD; Ivoclar vivadent, VITA Suprinity; VITA) were milled using a milling machine. For the fabrication of the crown scanned model file, the intaglio surface of the restoration was digitized using a contact scanner. Then, using the three-dimensional inspection software (Geomagic control X; 3D Systems), the process of the overlap of the crown designed model and the scanned model and 3-dimensional analysis was conducted. In addition, the marginal and internal fit of the crowns was evaluated by a silicone replication method. The difference among three types of single ceramic crown was analyzed using a Kruskal-Wallis H test, and Spearman correlation analysis was performed to analyze the correlation between machining precision and fitness (α=.05). Results: There was a significant difference in the machining precision and the marginal and internal fit according to the type of ceramic block (P<.001). In addition, the machining precision and the marginal and internal fit were positively correlated (P<.001). Conclusion: The marginal fit of crowns fabricated according to the types of ceramic blocks was within the clinically acceptable range (< 120 ㎛), so it can be regarded as appropriate machining precision applicable to all clinical as aspects in terms of the marginal fit.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.9 no.2
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• pp.270-275
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• 2008

The straight bevel gear for automobile part has been manufactured by the cold forging instead of the gear machining tool for the mass production. The application to CAD/CAM system has been necessary in order to develop the precision product quickly by forging through the minimization of trial and error and confirm the reproducibility. In the study, the straight bevel gear with the crown teeth has been modelled by the CAD/CAM system. The master gear after the gearing test has been machined after the modelling, NC data generation and verification. The die for forging and the jig for machining has been manufactured using the master gear.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2001.10a
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• pp.190-194
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• 2001

The integration of rapid prototyping and tooling has the potential for the rapid net shape manufacturing of three-dimensional parts with geometrical complexity. In this study, a new rapid prototyping process, transfer type of Variable Lamination Manufacturing (VLM-ST), was proposed to manufacture net shape of 3-D prototypes. In order to examine the efficiency and applicability of the proposed process, various 3-D parts, such as a world-cup logo, and extruded cross and a knob shape, were fabricated on the apparatus. In addition, the new rapid tooling process, which is a triple reverse process, was proposed to manufacture of 3-D functional part using VLM-ST prototypes and the plastic part of the knob shape was produced by the new rapid tooling process.

• Journal of Dental Rehabilitation and Applied Science
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• v.36 no.4
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• pp.254-261
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• 2020

Purpose: The purpose of this study was to assess the marginal and internal fit of interim crowns fabricated by two different manufacturing method (subtractive manufacturing technology and additive manufacturing technology). Materials and Methods: Forty study models were fabricated with plasters by making an impression of a master model of the maxillary right first molar for ceramic crown. On each study model, interim crowns (n = 40) were fabricated using three types of 3D printers (Meg-printer 2; Megagen, Zenith U; Dentis, and Zenith D; Dentis) and one type milling machine (imes-icore 450i; imes-icore GmbH). The internal of the interim crowns were filled with silicon and fitted to the study model. Internal scan data was obtained using an intraoral scanner. The fit of interim crowns were evaluated in the margin, absolute margin, axial, cusp, and occlusal area by using the superimposition of 3D scan data (Geomagic control X; 3D Systems). The Kruskal-wallis test, Mann-Whitney U test and Bonferroni correction method were used to compare the results among groups (α = 0.05). Results: There was no significant difference in the absolute marginal discrepancy of the temporary crown manufactured by three 3D printers and one milling machine (P = 0.812). There was a significant difference between the milling machine and the 3D printer in the axial and occlusal area (P < 0.001). The temporary crown with the milling machine showed smaller axial gap and higher occlusal gap than 3D printer. Conclusion: Since the marginal fit of the temporary crown produced by three types of 3D printers were all with in clinically acceptable range (< 120 ㎛), it can be sufficiently used for the fabrication of the temporary crown.

• Journal of Broadcast Engineering
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• v.3 no.1
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• pp.93-99
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• 1998

본 논문에서는 Ka-밴드 위성통신 송신주파수대역(30.085∼30.885 GHz)의 대역통과 필터를 유도성 fin-line 구조를 이용하여 분석, 설계 및 제작하였다. 도파관내의 공진기들이 전계면에 수직한 금속 fin으로 구성된 구조를 해석하는데 가장 적합한 모드정합법을 사용하여 설계하였다. 제작된 필터는 마이크로파대역 뿐만 아니라 밀리미터파대역의 주파수에서도 우수한 필터특성을 갖는다는 특징을 가지고 있으며, 상업용 도파관을 사용하는 대신에 가격이 저렴하고 가공이 용이한 알루미늄을 사용함으로써 대량생산이 가능하다. 또한 도파관내 금속삽입형태에 의한 대역 통과 필터의 구현이 아닌 유한한 두께를 갖는 포토-에칭된 유전체 기판을 삽입함으로써 제작성의 어려움을 해결하였다. 설계, 제작된 필터의 측정결과 통과대역내에서 1.6dBal만의 삽입손실과 18dB이상의 반사손실을 갖는 응답특성을 얻었으며 이론에 의한 계산치와 측정치와의 비교를 통해 본 논문에서 제안된 설계방법의 타당성을 입증하였다.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.38 no.10
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• pp.817-829
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• 2014

One of the main issues in tissue engineering has been the development of a three-dimensional (3D) structure, which is a temporary template that provides the structural support and microenvironment necessary for cell growth and differentiation into the target tissue. In tissue engineering, various biomaterials and their processing techniques have been applied for the fabrication of 3D structures. In particular, 3D printing technology enables the fabrication of a complex inner/outer architecture using a computer-aided design and manufacturing (CAD/CAM) system, and it has been widely applied to the fabrication of 3D structures for tissue engineering. Novel cell/organ printing techniques based on 3D printing have also been developed for the fabrication of a biomimetic structure with various cells and biomaterials. This paper presents a comprehensive review of the functional scaffold and cell-printed structures based on 3D printing technology and the application of this technology to various kinds of tissues regeneration.

• Proceedings of the KAIS Fall Conference
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• 2007.05a
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• pp.279-282
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• 2007

본 연구의 목적은 조정을 거친 수치지도를 이용하여 3차원 도시공간모델을 생성하는 자동제작기를 제안하는 것이다. 일반적인 디지털 도시공간모탤 제작방식에 대해 분석하여 3차원 도시공간모델 제작에 필요한 소요정보 및 공간제작함수(기능, Method} 등을 추출한다. 수치지도에서 3차원 도시공간모델 제작에 필요한 정보를 추출하고 이런 정보들을 가공하여 모텔제작에 사용가능한 정보로 바꾸어 준다. 또한 수치지도를 이용하여 3차원 모델을 제작할 때 사용자가 필요로 하는 부가정보들을 수동으로 입력할 수 있도록 한다. 수치지도에서 얻는 정보에 공간제작함수를 적용해서 3차원 모텔을 제작한다. 수치지도가 2차원지도로만 활용되고 있는 현실이며 수치지도의 다양한 3차원 정보를 이용한 3차원 도시 공간모델 자동제작을 제안함으로써 재래식 모델제작에 필요했던 대량의 시간과 노동력을 절감할 것이고 또한 제작된 도시공간모텔은 건축이나 도시설계분야에서 보다 경제적이고 보다 쉽게 활용될 수 있을 것이라고 기대된다.

• Journal of the Korean Society for Precision Engineering
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• v.21 no.9
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• pp.41-47
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• 2004

As mechanical structures are minimized, the demand on micro dies and molds has increased. Machining complex 3D shapes requires fabrication procedures for preparing the electrodes. Micro electrical discharge milling using a simple shape electrode can produce 3D micro structure. In this paper the machining characteristics of micro electrical discharge milling according to depth of cut and capacitance are investigated. The machining time is diminished when simple tool-paths and algorithms for changing the feedrate are applied. But a distorted bottom shape and a tapered wall shape are inevitable after machining. The distorted bottom shape and the taper angle of wall are reduced by finish machining.