Flow visualization of filling process during micro-injection molding / S.-Y. Yang in INTERNATIONAL POLYMER PROCESSING, Vol. XVII, N° 4 (12/2002)  

[article]  inINTERNATIONAL POLYMER PROCESSING > Vol. XVII, N° 4 (12/2002) . - p. 354-360 Titre : Flow visualization of filling process during micro-injection molding Type de document : texte imprimé Auteurs : S.-Y. Yang, Auteur ; S. C. Nian, Auteur ; C. Sun, Auteur Année de publication : 2002 Article en page(s) : p. 354-360 Note générale : Bibliogr. Langues : Anglais (eng) Index. décimale : 668.9 Polymères Résumé : Micro-injection molding has been under development for the mass manufacture of micro parts. This paper presents fundamental research on the filling characteristics during micro-injection molding. Flow visualization was employed to observe the fast filling process. A lab-made impact type micro-injection machine was developed and used in this study. Filling of 4 x 4 x 0.2 mm3 and 2 x 2 x 1 mm3 cavities in quartz glass molds was recorded with a high-speed video camera. The effects of the processing conditions on the filling behaviors are systematically studied. The processing parameters include air pressure, mold temperature, and melt temperature. Based on the analysis of flow patterns, it was found that the melt fronts advanced quickly and filled the cavity in less than 0.1 seconds. The filling process can be divided into impact-filling and pressure-filling stages. Mold temperature and air pressure are found to be the dominant processing parameters. Note de contenu : - EXPERIMENTAL SET-UP : Impact type micro-injection machine - Mold construction - Image capture system and operation procedure - Processing conditions - RESULTS AND DISCUSSION : Flow visualization of the filling process during filling of the shell-shaped cavity - Flow visualization of the filling process during filling of the block-shaped cavity - Effects of processing conditions in filling behaviors during micro-injection molding - Effects of air pressure - Effects of mold temperature - Effects of melt temperature DOI : 10.3139/217.1706 En ligne : https://drive.google.com/file/d/1DCPLSdI11t9o9-8P3ETib79_x-4SfevY/view?usp=drive [...] Format de la ressource électronique : Pdf Permalink : https://e-campus.itech.fr/pmb/opac_css/index.php?lvl=notice_display&id=16039 [article]

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Flow visualization of filling with aid of colored billets during impact micro-injection molding / S. C. Nian in INTERNATIONAL POLYMER PROCESSING, Vol. XIX, N° 4 (12/2004)  

[article]  inINTERNATIONAL POLYMER PROCESSING > Vol. XIX, N° 4 (12/2004) . - p. 402-407 Titre : Flow visualization of filling with aid of colored billets during impact micro-injection molding Type de document : texte imprimé Auteurs : S. C. Nian, Auteur ; S.-Y. Yang, Auteur Année de publication : 2004 Article en page(s) : p. 402-407 Note générale : Bibliogr. Langues : Anglais (eng) Index. décimale : 668.9 Polymères Résumé : Injection molding of thermoplastic parts with micro shotweight has been developed for many Micro-Electro-Mechanical (MEMS) applications. A lab-made high speed impact type micro-injection machine was developed to perform the microinjection molding. Many phenomena regarding impact microinjection molding is not clear and needs systematical investigation. In this study, the filling phenomena during impact microinjection was observed and investigated. Molds of spiral cavity of four different depths were constructed and employed. One side of the cavity was implemented with transparent window to observe the filling, and the filling phenomena were recorded with a high-speed video camera. To aid detailed observation, in the injection sleeve of the machine, sequential transparent and colored billets were inserted. The recorded images of filling flows of the colored melt in the spiral cavity were used for visualization and analysis of the filling with impact-type micro-injection molding machine. It is observed that melt behind from the sleeve will flow through the core of melt ahead and lead the melt front. Fountain flow in high speed micro-injection molding is dominant. During penetration, the colored melt, which is behind the transparent melt originally, is comparatively hot and flows along the core, following the inner side of core to seek shortest flow path. DOI : 10.3139/217.1841 En ligne : https://drive.google.com/file/d/1jOY94kWGCc0wJtZyrB3Kqf_5w_CDoz5N/view?usp=drive [...] Format de la ressource électronique : Pdf Permalink : https://e-campus.itech.fr/pmb/opac_css/index.php?lvl=notice_display&id=3274 [article]

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Molding of thin sheets using impact micro-injection molding / S. C. Nian in INTERNATIONAL POLYMER PROCESSING, Vol. XX, N° 4 (12/2005)  

[article]  inINTERNATIONAL POLYMER PROCESSING > Vol. XX, N° 4 (12/2005) . - p. 441-448 Titre : Molding of thin sheets using impact micro-injection molding Type de document : texte imprimé Auteurs : S. C. Nian, Auteur ; S.-Y. Yang, Auteur Année de publication : 2005 Article en page(s) : p. 441-448 Note générale : Bibliogr. Langues : Anglais (eng) Index. décimale : 668.9 Polymères Résumé : The micro-injection molding is used to fabricate ultra-thin polymeric components used in optoelectronics and biotechnology. Due to the extremely high flow resistance and fast heat transfer, ultra-thin parts is difficult to mold. In this study, a lab-made impact type micro-injection machine and a rapid heating/cooling system are used to perform the micro-injection molding. A mold with test-sheet cavities of thickness 100 lm and 200 lm are constructed. The molding capacity and the effects of processing conditions are systematically investigated. The processing conditions include the mold temperature, air pressure of accelerating cylinder, and air pressure of packing cylinder. The thicker parts have larger operation window. The high mold temperature reduces the area of short shot but induces more shrinkage and sink mark. The increase of air pressure in accelerating and packing cylinders can effectively reduce shrinkage. DOI : 10.3139/217.2008 En ligne : https://drive.google.com/file/d/1sUbivA9-Jl6f-QrsvAvQBeevDUat38sL/view?usp=drive [...] Format de la ressource électronique : Pdf Permalink : https://e-campus.itech.fr/pmb/opac_css/index.php?lvl=notice_display&id=2970 [article]

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Novel embossing system for replicating micro-structures on curved surfaces / S. C. Nian in INTERNATIONAL POLYMER PROCESSING, Vol. XXIX, N° 3 (07/2014)  

[article]  inINTERNATIONAL POLYMER PROCESSING > Vol. XXIX, N° 3 (07/2014) . - p. 364-370 Titre : Novel embossing system for replicating micro-structures on curved surfaces Type de document : texte imprimé Auteurs : S. C. Nian, Auteur Année de publication : 2014 Article en page(s) : p. 364-370 Note générale : Bibliogr. Langues : Anglais (eng) Catégories : Films plastiques Gaufrage à chaud Microstructures Polycarbonates Résines photosensibles Surfaces (technologie) Surfaces courbes Index. décimale : 668.4 Plastiques, vinyles Résumé : Hot embossing is widely used to replicate micro-structures on polymer plate surfaces. The polymer parts of curved surfaces with micro-structures have important functions in various optoelectronic components. However, due to the high precision needed for embossing machines and mold manufacturing, achieving uniform pressure on curved surfaces during the embossing process is difficult. This study modified conventional hot embossing processes to develop an elastic bag embossing system (EBES) for replicating micro-structures on curved surfaces. The pressure equalizing properties of the elastic bag enabled uniform application of pressure on curved surfaces embossed with a general hot compression machine. For the EBES-assisted hot embossing process, a nickel stamper was attached to the elastic bag to compress and replicate micro-structures on the PC film covering the mold surface with single direction curve. This study also developed an EBES-assisted UV exposure process that used a PDMS soft-mold attached to the elastic bag surface to compress the UV curable photoresist covering the surface of the convex lens. Micro-structures were then formed by exposing the photoresist. Experimental results showed that the EBES with Ni stamper could successfully replicated micro-structures onto a 200 mm × 200 mm curved PC film and that the EBES-assisted UV exposure could successfully produced a 50 mm diameter fresnel lens on a convex profile with material of UV photoresist. Experimental tests of pressure-sensitive film showed that EBES enables uniform application of pressure on curved surfaces during the embossing process on standard hot compression machines. The experimental results confirm that the EBES developed in this study is an efficient and economical method for replicating micro-structures on curved surface. Note de contenu : - EXPERIMENT : Setup for EBES-assisted hot embossing process - Setup for EBES-assisted UV exposure - RESULTS AND DISCUSSION : Embossing pressure distribution - Experimental results for EBES-assisted hot embossing process - Experimental results for EBES-assisted UV exposure DOI : 10.3139/217.2790 En ligne : https://drive.google.com/file/d/1FpVYjGOVkNZ_1q_-HRDMGrNnssmXTKyl/view?usp=drive [...] Format de la ressource électronique : Pdf Permalink : https://e-campus.itech.fr/pmb/opac_css/index.php?lvl=notice_display&id=21734 [article]

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