• Tribology and Lubricants
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• 제35권2호
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• pp.106-113
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• 2019

We investigated the application of tetrahedral amorphous carbon (ta-C) coatings to fabricate a glass lens manufactured using a glass molding process (GMP). In this work, ta-C coatings with different thickness (50, 100, 150 and 200 nm) were deposited on a tungsten carbide (WC-Co) mold using the X-bend filter of a filtered cathode vacuum arc. The effects of thickness on mechanical and tribological properties of the coating were studied. These ta-C coatings were characterized by atomic force microscopy, scanning electron microscopy, nano-indentation measurements, Raman spectrometry, Rockwell-C tests, scratch tests and ball on disc tribometer tests. The nano-indentation measurements showed that hardness increased with an increase in coating thickness. In addition, the G-peak position in the Raman spectra analysis was right shifted from 1520 to $1586cm^{-1}$, indicating that the $sp^3$ content increased with increasing thickness of ta-C coatings. The scratch test showed that, compared to other coatings, the 100-nm-thick ta-C coating displayed excellent adhesion strength without delamination. The friction test was carried out in a nitrogen environment using a ball-on-disk tribometer. The 100-nm-thick ta-C coating showed a low friction coefficient of 0.078. When this coating was applied to a GMP, the life time, i.e., shot counts, dramatically increased up to 2,500 counts, in comparison with Ir-Re coating.

• Design & Manufacturing
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• 제12권1호
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• pp.36-40
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• 2018

The car requires an inside mirror installed between the driver's seat and the passenger's seat to ensure the driver's rear and side view of the driver. Inside mirrors must always be attached to the vehicle to ensure the driver's visibility. Inside mirrors attached to the windshield of a vehicle are always exposed to direct sunlight and should be semi-permanently usable in hot and humid summer weather in Korea. Therefore, the mirror mount, which is the junction of the inside mirror, is particularly important in corrosion resistance and wear resistance suitable for humidity. Mirror mounts are currently difficult to manufacture due to their reliance on powder molding technology in advanced countries such as Japan and Germany. This paper focuses on the fabrication of high corrosion resistant stainless mirror mounts by vacuum sintering technique and focuses on the selection of materials suitable for the production of mirror mounts through experiments of 300 series stainless steel and 400 series stainless steel manufactured by vacuum sintering.

• 접착 및 계면
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• 제12권4호
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• pp.144-150
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• 2011

폴리스티렌을 저수축제로 사용하고 Zn-stearate를 이형제로 사용하여 함량변화에 따라 벌크 몰드컴파운드의 표면형태 및 기계적 물성에 미치는 영향을 고찰하였다. XPS, 접촉각 측정기 등을 이용하여 표면과 깊이 방향에 대한 원소함량과 접촉각을 측정하였고, 표면형태는 FESEM을 이용하여 관찰하였으며, 표면조도 측정은 AFM을 이용하였다. 저수축제를 첨가하지 않은 경우에 비교하여 저수축제를 9.0 wt% 첨가하였을 경우에는 체적수축률은 0.35%에서 0.05%로 감소하였으며, 표면조도는 $0.27{\mu}m$에서 $0.12{\mu}m$로 감소하였다. 이형제의 함량을 1.8 wt%에서 3.6 wt%로 증가시켰을 경우에는 이형제가 주로 표면에 존재하고 표면조도를 증가시키는 것을 확인하였다. 저수축제의 함량을 5.0 wt%에서 9.0 wt%로 증가시킴에 따라 굴곡탄성율과 충격강도가 약 30% 감소하였다.

• 한국진공학회지
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• 제19권2호
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• pp.96-104
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• 2010

NIL, S-FIL과 같은 각인 기술(Imprinting lithography)를 적용하기 위한 투명하고 단단한 복제 틀(replica hard mold)을 제작하여 고가의 원판(master)와 패턴이 형성되는 기판과의 접촉을 근본적으로 방지해 경제적인 공정이 가능함을 제안한다. 실리콘 웨이퍼(Si wafer)와 같은 원판(master)과 패턴 형성 시 사용되는 기판과 직접적인 접촉을 방지하기 위해 우선 액상 공정을 이용하여 비접착성 표면처리된 고분자 복제(polymer copy)를 매개체(carrier)로 단단한 복제 틀을 제작한다. 이렇게 제작된 단단한 복제 틀(replica hard mold)는 유리와 거의 같은 강도와 투명도를 나타내며, 각인 공정(imprinting process)에서 석영 틀, 실리콘 웨이퍼(quartz mold, Si wafer)과 같이 값비싼 원판(master)의 직접 사용을 대체하여 성공적으로 패턴을 구현할 수 있다.

• 전기학회논문지
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• 제66권6호
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• pp.962-967
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• 2017

The Diamond-Like-Carbon (DLC) coating is a new carbon-based amorphous material. Carbon ions in the plasma are electrically accelerated and collide with the substrate to form a thin film. This film has similar properties to diamonds such as high surface hardness, low coefficient of friction, corrosion resistance and durability that do not react with acids and bases. Also, since there is no thermal deformation, it can be printed at room temperature. and coated on almost all materials such as paper, polymer, ceramics and various metals even aspheric lens it is possible to mirror surface coating with excellent surface roughness. In this paper, we have analyzed the DLC film formed by Filtered Arc Ion Plating (Filtered AIP) process.

• Design & Manufacturing
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• 제15권3호
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• pp.7-12
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• 2021

Plastic injection molds used for rapid heating and cooling must minimize surface damage due to friction and maintain excellent thermal and low electrical conductivity. Accordingly, various surface treatments are being applied. The properties of Al₂O₃ coating and DLC coating were compared to find the optimal surface treatment method. Al₂O₃ coating was deposited by thermal spray method. DLC films were deposited by sputtering process in room temperature and high temperature PECVD (Plasma enhanced chemical vapor deposition) process in 723 K temperature. For the evaluation of physical properties, the electrical and thermal conductivity including surface hardness, adhesion and wear resistance were analyzed. The electrical resistance of the all coated samples was showed insulation properties of 24 MΩ/sq or more. Especially, the friction coefficient of high temp. DLC coating was the lowest at 0.134.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2007년도 추계학술대회 논문집
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• pp.364-367
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• 2007

In nano-imprint lithography (NIL) process, which has shown to be a good method to fabricate polymeric patterns, several kinds of pattern defects due to thermal effects during polymer flow and mold release operation have been reported. A typical defect in NIL process with high aspect ratio and low resist thickness pattern is a resist fracture during the mold release operation. It seems due to interfacial adhesion between polymer and mold. However, in the present investigation, FEM simulation of NIL molding process was carried out to predict the defects of the polymer pattern and to optimize the process by FEA. The embossing operation in NIL process was investigated in detail by FEM. From the analytical results, it was found that the lateral flow of polymer resin and the applied pressure in the embossing operation induce the weld line and the drastic lateral strain at the edge of pattern. It was also shown that the low polymer-thickness result in the delamination of polymer from the substrate. It seems that the above phenomena cause the defects of the final polymer pattern. To reduce the defect, it is important to check the initial resin thickness.

• 한국응용과학기술학회지
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• 제29권1호
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• pp.13-18
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• 2012

금속 주조시 사용되는 탄소이형제를 카본블랙과 점증제 겸 알데하이드 화합물의 경화제로 사용될 수 있는 수용성 고분자인 잔탄검(X-gum), 카르복시메틸셀룰로오스(CMC)을 혼합하여 제조하였다. 이 때 카본블랙의 안정한 분산을 위하여 0.25 wt%의 X-gum 또는 1.0 wt%의 CMC가 적당하였다. 1.0 wt% 보다 낮은 농도의 CMC를 사용했을 경우 카본블랙이 매우 쉽게 층분리되었다. 유리판에 대한 부착력은 경화제와, 구르탈알데하이드 및 사슬연장제인 올리고당의 양에 비례하였으며. X-gum으로 제조된 탄소 이형제는 CMC를 이용해 제조된 것보다 유리에 대한 부착력이 우수하였다. 결과적으로 본 실험의 최적 조건에서 제조된 탄소이형제는 친환경적으로 주조시에 적용할 수 있을 것으로 판단된다.

• Design & Manufacturing
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• 제10권2호
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• pp.18-23
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• 2016

Injection molded thermoplastic parts may need to be coated to facilitate paint adhesion, or to satisfy other surface property requirements, such as appearance, durability, and weather resistance. In this paper, a two-component polyurethane metering system was developed for the simultaneous injection and surface coating of a plastic substrate. The system was composed of storage tanks, feed pumps, axial piston pumps, mixing head. The tank was designed to be double-jacket structured and fabricated for polyol and isocyanate, respectively. A temperature chamber was used to maintain the material temperature to be $80^{\circ}C$ during flowing from storage tank to mixing head. Inside the chamber, feed pump, low pressure filter, high pressure pump, high pressure filter, pressure sensor, flow meter were installed. A mixing head of L-type was used for homogeneous mixing of polyol and isocyanate. Inside the mixing head, a cartridge heater and a temperature sensor were installed to control the temperature of the materials. The flow rate of axial-piston pump was controlled by using closed-loop feedback control algorithm. The input flow-rates were compared with the measured values. The output error was 6.7% for open-loop control, whereas the error was below 2.2% for closed-loop control. In addition, the pressure generated through mixing-head nozzle increased with increasing flow rate. It was found that the pressure drop between metering pump and mixing-head nozzle was almost 10 bar.

• Design & Manufacturing
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• 제7권1호
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• pp.28-33
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• 2013

During the cold forming, due to high working pressure acting on the die surface, failure mechanics must be considered before die design. One of the main reasons of die failure in industrial application of metal forming technologies is wear. The mechanisms of wear are consisted of adhesion, abrasion, erosion and so on. Die wear affects the tolerances of formed parts, metal flow, and costs of process. The only way to control these failures is to develop a prediction method on die wear suitable in the design state in order to optimize the process. The wear system is used to analyse 'operating variables' and 'system structure'. In this study, with AISI D2, AISI 1020, AISI 304SS materials, a series of the wear experiments of pin-on-disk type to obtain the wear coefficients from Archard's wear model and the upsetting processes are carried out to observe the wear phenomenon during the cold forming process. The analysis of upsetting processes are performed by the rigid-plastic finite element method. The result of the analysis is used to investigate the die wear the processes, and the analysis simulated die wear profiles are compared with the experimental measured die wear profiles.