• 대한기계학회:학술대회논문집
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• 대한기계학회 2001년도 추계학술대회논문집A
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• pp.766-771
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• 2001

Gas-assisted injection molding is an innovative low-pressure injection molding technique that can provide numerous benefits such as reduced part warpage, excellent surface quality without sink marks, low injection pressure, and greater design flexibility. However, the adoption of gas-assisted injection molding may cause unexpected defects if the gas channel design is not conducted properly. The objective of this paper is to broaden the understanding of gas-assisted injection molding by summarizing the design procedures and experimental results of the gas-assisted injection molding of a 17" flat monitor front cover. The gas channels were designed by using Moldflow(MF/GAS) simulations and a 450 ton injection molding machine with a 5 stage pressure control gas kit was used in the experiments.

• 소성∙가공
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• 제21권1호
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• pp.36-41
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• 2012

Gas Assisted Injection Molding is a relatively new low-pressure injection molding technique that provides benefits such as reduced part warpage, excellent surface quality without shrink marks, greater design flexibility, etc. In the gas assisted injection molding process, the injected pressurized nitrogen gas flows through designed gas channels and forms hollow sections within the part. However, due to the characteristics of the gas, the design of the gas channels which are the paths for the injected gas is important in order to avoid defects such as gas blowout, fingering, etc. Therefore, in this study, the gas channel design for gas assisted injection molding of exterior display panels was conducted by examining the results of three CAE analyses. The designed gas channel was verified by conducting tryouts using a 450 ton injection molding machine with 3-stage pressure controlled gas kit. In addition, the hollow shapes which were formed by the gas with the installed gas channels were examined by examining the cross sections of the prototypes that were produced. As a result, it was found that exterior display panels can be produced without any defect by applying the gas assisted injection molding technique.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2001년도 추계학술대회논문집A
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• pp.772-777
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• 2001

The gas-assisted injection molding process is often perceived to be unpredictable, because of the extreme sensitivity of the gas. Since a slight change in design or process parameters can significantly change the resulting gas penetration, few designers and molders have the level of experience with the new gas-assisted injection molding process required for the development of new parts. This paper is concerned with the unified molding for a thick cosmetic chest by using gas-assisted injection molding. CAE analysis was carried out to design the part and the gas channel without inducing sink marks. And based on the part weight measurement, the processing parameters to control gas penetration percentage were chosen through the method of design of experiments. A thick cosmetic chest was successfully produced using the gas assist technology. The sink mark issue associated with the conventional injection molded parts was resolved. Weight savings and cycle-time reduction were also achieved.

• 소성∙가공
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• 제10권5호
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• pp.402-410
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• 2001

The gas-assisted injection molding process is often perceived to be unpredictable, because of the extreme sensitivity of the gas. Since a slight change in design or process parameters can significantly change the resulting gas penetration, few designers and molders have the level of experience with the new gas-assisted injection molding process required for the development of new parts. This paper is concerned with the unified molding for a thick cosmetic chest by using gas-assisted injection molding. CAE analysis was carried out to design the part and the gas channel without inducing sink marks. And based on the part weight measurement, the processing parameters to control gas penetration percentage were chosen through the method of design of experiments. A thick cosmetic chest was successfully produced using the gas assist technology. The sink mark issue associated with the conventional injection molded parts was resolved. Weight savings and cycle-time reduction were also achieved.

• Korea-Australia Rheology Journal
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• 제16권1호
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• pp.27-33
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• 2004

Application of gas assisted injection molding has been expanded during last two decades because of many advantages such as design flexibility, dimensional stability, reduction of machine tonnages, and so on. However, the surface defects including hesitation mark and gloss difference are observed for thick parts. Difficulties in lay-out of the gas channel and processing condition are another disadvantages. Liquid gas assisted injection molding(LGAIM), in which a liquid with a boiling point lower than the temperature of the polymer melt is injected into the melt stream, and travels with the melt into the mold where it vaporizes and pushes the melt downstream and against the cavity walls to create hollow channels within the part, is a good alternative of the conventional gas assisted injection molding especially in manufacturing simple and very thick parts. Though this is a new frontier of the innovation in the injection molding industry, there is no guideline for the design and processing conditions. In this paper, theoretical analysis has been made to describe the hollow formation dynamics in LGAIM. This model provides an insight into LGAIM process: explains why LGAIM has advantages over conventional gas assisted injection molding, and gives a guideline for the design and processing conditions.

• 소성∙가공
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• 제21권2호
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• pp.107-112
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• 2012

Gas-assisted injection molding(GAIM) produces parts with hollow internal sections. The technique offers benefits to powder injection molding(PIM), with lower material usage and reduced time for de-binding processes. In this study, the effects of processing parameters on gas penetration length of gas-assisted powder injection molding(GAPIM) were investigated for SUS316L stainless steel powder feedstock. Experiments were planned based on the Taguchi method, involving processing variables such as melt temperature, shot size, gas pressure, and gas delay time. The most significant parameters affecting gas penetration length were gas delay time and shot size, while the effects of melt temperature and gas pressure was relatively insignificant.

• 한국정밀공학회지
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• 제17권10호
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• pp.102-109
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• 2000

In the present study, gas-assisted molding and structural vibration analysis of hollow long cylinder with the variation of gas injection pressure are performed. Though there are so many parameters such as delay time, injection pressure, and gas pressure on gas-assisted molding, the latter has the most dominant effect on this process. Therefore, the present paper deals with the effects of gas pressure on the dynamic stiffness of the model by means of vibration analysis and then suggests the fundamental materials which can be directly adapted to manufacturing lines.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 1999년도 춘계학술대회논문집
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• pp.131.2-135
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• 1999

This study focuses on part quality and cycle times under gas-assisted injection molding(GIM) of housing molded parts. The position of the gas channel was estabished near to parting line at the end of last locations to fill. Applied hot runner and valve gates the gas was introduced directly into the mold cavity via gas pin. As GIM was applied the introduced directly into the mold cavity via gas pin. As GIM was applied the conclusion reached as follows. I) The quality of appearance was improved by reducing sink marks and scratches of texture ii) The realibility was improved by preventing warpages and reinforcing rigidity through optimum gas channel layout iii)It is enable to use small size of injection molding machine step by step as GIM was accomplished low pressure and reduced clamp forces against CIM iv)The productivity were improved by reducing cycle times.

• 소성∙가공
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• 제8권3호
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• pp.276-283
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• 1999

This study focuses on part quality and cycle times under gas-assisted injection molding (GIM) of box shape molded parts. The position of the gas channel was established near to parting line at the end of last locations to fill. Applied hot runner and valve gates, the gas was introduced directly into the mold cavity via gas pin. As GIM was applied, the conclusion reached as follows. I) The quality of appearance was improved by reducing sink marks and scratches of texture. ii) The reliability was improved by preventing warpages and reinforcing rigidity through optimum gas channel layout. iii) It is enable to use small size of injection molding machine step by step as GIM was accomplished low pressure and reduced clamp forces against CIM. iv) The productivity were improved by reducing cycle times.

• 한국분말재료학회지
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• 제24권5호
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• pp.351-356
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• 2017

Tin dioxide nanoparticles are prepared using a newly developed synthesis method of plasma-assisted electrolysis. A high voltage is applied to the tin metal plate to apply a high pressure and temperature to the synthesized oxide layer on the metal surface, producing nanoparticles in a low concentration of sulfuric acid. The particle size, morphology, and size distribution is controlled by the concentration of electrolytes and frequency of the power supply. The as-prepared powder of tin dioxide nanoparticles is used to fabricate a gas sensor to investigate the potential application. The particle-based gas sensor exhibits a short response and recovery time. There is sensitivity to the reduction gas for the gas flowing at rates of 50, 250, and 500 ppm of $H_2S$ gas.