• 한국생산제조학회지
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• 제19권6호
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• pp.847-851
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• 2010

It was attempted to develop an auto part by over molding injection mold that produces precision products in high productivity with use of an eco-friendly TPE substitute material for NBR. NBR is currently used in motor gear cover, one of the key parts in motor module for auto doors. Gear cover is composed of plastics and rubber mostly today, which requires a two (2) step process for production using two presses of different types. A hot press is used at this time for forming the rubber, which has drawback of requiring a rather long forming time of 400 seconds for one forming process. Even though this difficulty is overcome by reducing production time through employment of multi-cavity molds, time for forming process must be shortened for improvement of the productivity eventually, and the existing method of insert injection for products that have been formed with plastic material must be outgrown. In this point of view, over molding injection using TPE has a big advantage. Forming time is shortened to 54 seconds, and working the two (2) processes in series by one (1) press could solve the durability problem caused by deflection of the plastics, not to mention shortening the process time. Enhancement of productivity by almost 80% and improvement in the accuracy of the product could thus be achieved.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2006년도 춘계학술대회 논문집
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• pp.529-530
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• 2006

Manufacturing industry is changing rapidly. Prototyping with rapid manufacturing is a part of every business in many companies and prototypes are used efficiently as a part of the production development process. Sheet metal forming has traditionally been a technology area where prototyping has been extremely expensive and efficient options for low volume have been limited. This paper describes the process for incremental sheet forming technologies to make the prototype for a brake dust shield of vehicles, which includes the remodeling method to make a base mold and tool path for sheet metal forming and 5-axes laser cutting machine to trim the prototype product.

• 한국생산제조학회지
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• 제23권6호
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• pp.590-595
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• 2014

We have investigated anamorphic prism lenses with distortions of 0.3-0.5%. We designed the plastic triangular lens and confirmed the minimum resolution using MTF graphs. Also we confirmed that the SVGA optical system can realize a resolution of $864{\times}648$ 56 megapixels. A distortion of about 0.5% aberration appears in the maximum field, and a finite beam aberration of about $15{\mu}m$ is confirmed. We made a mold based on the design data and completed the prism lens through exodus molding. We confirmed the shape error (< $30{\mu}m$) and surface roughness (> 40 nm) of the three sides. We made the video-information-display prototype glasses using prism lens by measuring the performance, we determined the distortion aberration (0.3%) and SVGA resolution. Our approach will enable fabrication of a portable large-screen display device for glasses and sunglasses for the domestic market and, after 2015, for the world market.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2010년도 제35회 추계학술대회논문집
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• pp.707-710
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• 2010

KSLV-I 킥모터 노즐 개발에 있어서 가장 중요한 개발품은 노즐 구동에 필요한 플렉시블 씰 개발이다. 특히 플렉시블 씰 제작 기술의 확보는 킥 모터 노즐 개발에 있어서 핵심 개발 사항 중에 하나였다. 킥모터 플렉시블 씰 제작에 사용된 방법은 금형에 순서대로 배열된 보강재 사이에 고무를 주입하는 인젝션 방식을 사용하였다. 플렉시블 씰 제작을 통해 금형 설계 기술, 고무 인젝션 방법, 성형 공정을 확립하였다. 제작된 플렉시블 씰은 X-Ray 검사를 통해 내부 접착 상태 및 보강재/고무 배열 상태를 확인하였다.

• 한국기계가공학회지
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• 제9권1호
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• pp.81-86
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• 2010

This paper investigated into process characteristics of AlTiN coated layers for machining to the direction of upper and lower in plastic mold material (KP-4) with the cemented carbide ball endmill with the diameter of 8mm coated AlTiN layers (1~4) step by step using machining center. The material used in experiments was KP-4 that was machined by three types of inclined angles; $15^{\circ}$, $30^{\circ}$ and $45^{\circ}$ As estimated mechanical properties of AlTiN coated layers, it was shown the most result in the condition of three layered coating that the coating that the coating depth, the hardness of the coated layer and the surface roughness of the coated layer were $13{\mu}m$, Hv 3027.3 and $0.042{\mu}m$, respectively. The cutting component was better at the condition of upper direction than that of lower direction in all experimental conditions and indicated to be less which the bigger angle of the material was increased the effective diameter of the tool.

• 한국기계가공학회지
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• 제13권4호
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• pp.50-55
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• 2014

Currently, flat cover glasses are widely applied to mobile devices. However, for a good design and for convenience of use, curved cover glasses are in demand. Thus, many companies are attempting to produce curved cover glasses using a shaving technique, but the production efficiency is very low. Therefore, a molding technique has been adopted to increase the efficiency of curved glass production systems. For a glass molding system, a uniform temperature distribution of the mold is crucial to produce high-quality curved cover glasses. Before setting the heating conditions of the molding system for a uniform temperature distribution by a thermal analysis, verification is required. Therefore, in this study, temperature measurements were conducted for a prototype molding system and the experimental results were compared with simulation computations. The temperatures of the heating block surface were in good agreement with the computational results for transient and steady conditions.

• 한국기계가공학회지
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• 제13권6호
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• pp.73-81
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• 2014

In this paper, multiple gate locations and process conditions under concern are automatically optimized by considering robustness to minimize the injection pressure required to mold an automotive dashboard. Computer simulation-based experiments using orthogonal arrays(OA) and a design-range reduction algorithm are consolidated into an iterative search scheme, which is then used as a tool for the optimization process. The robustness of a design is evaluated using an OA-based simulation of process fluctuations due to noise as well as the signal-to-noise ratio. The optimal design solution for the automotive dashboard shows that the robustness of the injection pressure is significantly improved when compared to the initial design. As a result, both the die clamping force and the pressure distribution in the part cavity are also much improved in terms of their robustness.

• 한국기계가공학회지
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• 제12권6호
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• pp.30-36
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• 2013

An FFD(flexible fine die) is an embossed mold that consists of a thin plate ranging from 0.6 to 3 mm in thickness. FFDs are primarily used for cutting LCD films and F-PCB sheets. In the high-speed micro-milling process of flexible fine dies, the lubrication and cooling of the cutting edges is very important from the aspect of eco machining and cutting performance. In this paper, a comparative study of tool wear and surface roughness between cutting fluid and hybrid lubrication for eco-machining of FFD was conducted for processes of high-speed machining of highly hardened material (STC5, HRC52). Especially, the incorporated fluid method for eco machining, in which the cutting performances can be simultaneously measured, was introduced. The machining results show that hybrid lubrication, instead of conventional cutting fluid, leads to excellent tool wear and surface roughness and represents the proper conditions for eco micro-machining of flexible fine dies.

• 한국기계가공학회지
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• 제16권5호
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• pp.157-165
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• 2017

The high-pressure resin transfer molding (HP-RTM) technology has been commercialized for fast production of fiber reinforced composite materials. The high-pressure mixing head was one of the most core component of the HP-RTM process. In this study, a mixing head was systematically designed, manufactured and evaluated. This mixing head was composed of a nozzle, a mixing chamber, a cleaning piston part, and an internal mold release part. In actual, a straight-type structure was newly designed instead of the conventional L-type structure for improving the maximum mixing pressure and mixing ratio precision. The performance of mixing head was showed maximum mixing pressure of 15.22MPa and mixing ratio precision of 0.12%. CFRP molding experiments were successfully obtained a 6~11 laminating carbon sheet using HP-RTM presses and specimen molds.

• 한국생산제조학회지
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• 제18권6호
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• pp.697-701
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• 2009

A simple method for the fabrication of porous nano-master for the anti-reflection effect on the transparent substrates is presented. In the conventional fabrication methods for antireflective surface, coating method using materials with low refractive index has usually been used. However, it is required to have a high cost and long processing time for mass production. In this paper, we developed a porous nano-master with anti-reflective surface for the molding stamper of the injection mold, hot embossing and UV imprinting by using the aluminum anodizing process. Through two-step anodizing and etching processes, a porous nano-master with anti-reflective surface was fabricated at the large area. Pattern size Pore diameter and inter-pore distance are about 130nm and 200nm, respectively. In order to replicate anti-reflective structure, hot embossing process was performed by varying the processing parameters such as temperature, pressure and embossing time etc. Finally, antireflective surface can be successfully obtained after etching process to remove selectively silicon layer of AAO master.