• 한국정밀공학회지
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• 제32권11호
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• pp.953-960
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• 2015

The thermoforming process has been widely used to manufacture medium- and large-sized plastic parts because of the relatively low cost and high productivity, as compared with other plastic forming processes. One of current salient issues of thermoforming industries is the reduction of trial and error during the production of the thermoformed product. Hence, there is a significant increasing interest in the thermoforming analysis by the thermoforming industries. The goal of this paper is to investigate a methodology of the three-dimensional thermoforming analysis for medium- and large-sized plastic parts. There is a discussion about methodologies of thermoforming analysis, as well as material modeling, and three-dimensional finite element analysis. Furthermore, there is an examination, through case studies, about the applicability of the proposed methodology concerning the thermoforming analysis.

• Design & Manufacturing
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• 제12권2호
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• pp.5-10
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• 2018

Vacuum-assisted thermoforming is one of the critical steps for successful application of film insert molding(FIM) to parts of complex shape. In this study, the simulations and experiments of thermoforming processes were performed to investigate the effects of process conditions on thickness distribution and printed pattern deformation of films in vacuum-assisted thermoforming. The film thickness uniformity increased with decreasing film heating time, whereas it increased with increasing vacuum delay time. After thermoforming of films with uniform pattern space of 5mm, the maximum space was 9.432mm. Based on the simulation, a modified pattern was calculated to obtain uniform spaces after thermoforming. In the experiments for film with the modified pattern, the maximum space appeared 5.837mm. In, addition. the predicted patterns were in good agreement with the experimental results.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2008년도 춘계학술대회 논문집
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• pp.281-284
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• 2008

Film insert melding is one of the surface processes that enhances functional or aesthetic qualities of an existing product's surface. In general, film insert molding consists of three processes including thermoforming, trimming and injection molding. Thermoforming, which is the first process of film insert molding, is the most important process because the variation of film thickness has an effect on the mold design and process conditions for the subsequent processes, that are, trimming and injection molding. This study is focused on predicting the film thickness distribution through film insert thermoforming process using commercial FEM code. In order to describe rheological behavior of thermoplastic film (ABS), G'Sell's viscoelastic constitutive law was adopted. The numerical model of film insert thermoforming was established, and the simulation to predict film thickness distribution was performed. Comparison between the results of simulation and experiment was made to validate the proposed finite element analysis.

• 대한기계학회논문집A
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• 제40권5호
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• pp.505-511
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• 2016

이 연구에서는 3차원 진공 열성형 해석을 통하여 3개의 캐비티를 가지는 냉장고 내상의 진공 열성형 특성을 분석/고찰 하고자 한다. 3개의 캐비티를 가지는 냉장고 내상 금형의 3차원 모델을 이용하여 냉장고 내상 제품의 기초 성형성을 분석하였다. 고온 인장시험을 수행하여 진공 열성형 재료에 대한 물성데이터 도출과 재료 특성 분석을 하였다. 3개의 캐비티를 가지는 냉장고 내상의 열성형 공정의 세부 공정들을 설계하고 세부 공정들에 적합한 유한요소해석 모델을 개발하였다. 각 세부 공정들에 대한 3차원 유한요소해석을 수행하여 제품의 변형 형상 및 두께 분포를 분석하였다. 최종적으로 3개의 캐비티를 가지는 냉장고 내상의 성형성과 진공 열성형 특성을 고찰하였다.

• 한국정밀공학회지
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• 제29권9호
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• pp.946-957
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• 2012

The objective of this paper is to investigate into the development of a thin flat panel photo-bioreactor case with characteristics shapes. The thin flat panel photo-bioreactor case was designed to be manufactured from a plastic thermoforming process. A proper design with a relatively high rigidity was obtained through the structural analyses for different designs of the photo-bioreactor case. The thermoforming analyses were performed. From the results of the thermoforming analyses, a proper forming condition and the formability of the designed plastic photo-bioreactor case were estimated. The thermoforming moulds for the flat panel photobioreactor cases were manufactured. The thermoforming experiments were performed to examine the manufacturability of the designed flat panel photo-bioreactor cases. From the results of the thermoforming experiments, it was shown that thin flat panel photo-bioreactor cases with characteristic shapes can be manufactured from the designed thermoforming mould and process.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2008년도 춘계학술대회 논문집
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• pp.819-820
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• 2008

• 대한기계학회:학술대회논문집
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• 대한기계학회 2007년도 춘계학술대회B
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• pp.2528-2533
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• 2007

Thermoforming is one of the most versatile and economical processes available for the manufacturing polymer products. The drawback of thermoforming is difficult to get uniform thickness of final products. For the distribution of thickness strongly depends on the temperature distribution of sheet, the adjustment of heater power is very important In this paper, an optimization study for getting uniform temperature distribution was carried out using dual optimization steps. At first, the steady state optimal distribution of heater power is searched by numerical optimization to get uniform temperature of sheet surface. In the second step, time-dependent optimal heater inputs have been found out to decrease the temperature difference through the direction of thickness using Rseponse Surface Method and D-optimal method. The optimization results show that the time-dependent optimal heater power distribution gives acceptable uniform sheet temperature in the field of forming temperature..

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2003년도 The Korea-Japan Plastics Processing Joint Seminar
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• pp.63-66
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• 2003

Thermoforming of fiber reinforced thermoplastic (FRTP) braided tubes was studied as a new forming technique. FRTP braided tubes with four plies are fabricated by the pressure bonding method are used in thermoforming. Bulge forming, bending process, pipe fittings and FE analysis are carried out in this study. In bulge forming the composite tube can be expanded up to about two times initial diameter. The suggested bending process can be obtained bent products with various bending radii. In pipe fitting it is possible to fabricate T-shape fitting, cross fitting and two-branch fitting. These results exhibit developed forming processes become useful processes for textile composite tubes.

• 소성∙가공
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• 제22권3호
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• pp.171-177
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• 2013

Vacuum-assisted thermoforming is one of the critical steps for successful application of film insert molding (FIM) to make parts of complex shape. If the thickness distribution of the formed film is non-uniform, then cracking, deformation, warpage, and wrinkling can easily occur at the injection molding stage. In this study, the simulation of thermoforming was performed to predict the film thickness distribution, and the results were compared with experiments. Uniaxial tensile tests with a constant crosshead speed for various high temperatures were conducted to investigate the stress-strain behavior. An instance of yielding occurred at the film temperature of $90^{\circ}C$, and the film stiffness increased with increasing crosshead speed. Two types of viscoelastic models, G'Sell model, K-BKZ model, were used to describe the measured stress-strain relationship. The predicted film thickness distributions were in good agreement with the experimental results.

• 한국복합재료학회:학술대회논문집
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• 한국복합재료학회 2004년도 추계학술발표대회 논문집
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• pp.131-134
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• 2004

In this paper, a representative unit volume (RUV) model was employed to simulate thermoforming process of carbon fabric-polymeric foam sandwich structures. Thermoforming simulations, which capture crimp angles and amplitude changes of carbon fabric with respect to different types of foams under the operating pressure were conducted with the help of RUV model. Changed shapes of tow structure after thermoforming were reflected in the two dimensional to determine mechanical properties of skin parts, i.e_ carbon fabric composites after thermoforming. Bending simulations with respect to different foam systems as well as different moduli of carbon fabric composites were successfully carried out by using properties obtained from two-dimensional analyses.