PIM기술을 이용한 마이크로 부품 성형기술

이원식(W.S. Lee),고세현(S.H. Ko),장진만(J.M. Jang),김일호(I.H. Kim) 한국소성가공학회 2009 한국소성가공학회 학술대회 논문집 Vol.2009 No.5

Manufacturing technology of micro spur gear and micro mold by micro PIM were studied with stainless steel feedstock. For molding of gears, micro mold with gear cavity of 1.2㎜ in diameter was produced by wire EDM. The proper injection pressure was selected to 70bar by observation and measuring of shapes and shrinkage of gears before/after sintering. For fabrication of micro mold, a tiny polymer gear was produced by injection into the mold. Then, 316L feedstock was again injected/compressed on the polymer gear and debinded together with polymer gear followed by sintering. As a result, another metal mold with gear cavity reduced to about 20% was fabricated and through repetition of this process chain, micro gear mold with cavity about below 800 um was finally obtained. In reduction of size by injection/compression molding, height of gear tooth was shrunk more and the effort for decrease of roughness of micro cavity were carried out ultrasonic polishing and as a result, the roughness in cavity decreased from 3-4 um to about 200nm.

Fully-Integrated Numerical Analysis of Micro-Injection Molding with Localized Induction Heating

Keun Park,Hyeju Eom,Sang Ik Lee 한국소성가공학회 2010 기타자료 Vol.2010 No.6

High-frequency induction is an efficient way to heat mold surface by electromagnetic induction in a noncontact procedure. Due to its capability of rapid heating and cooling of mold surface, it has been recently applied to the injection molding of micro/nano structures. The present study investigates a localized heating method involving the selective use of mold materials to enhance the heating efficiency of high-frequency induction heating. A composite injection mold consisting of ferromagnetic material and paramagnetic material is used for localized induction heating. The feasibility of the localized heating method is investigated through numerical analyses in terms of its heating efficiency for localized mold surfaces and the resulting flow characteristics in a micro-channel. To take into account the effects of thermal boundary conditions of the localized induction heating, a fully-integrated numerical analysis effectively connecting electromagnetic field calculation, heat transfer analysis, thermal stress analysis, and injection molding simulation is carried out. The proposed integrated simulation is applied to the injection molding of a rectangular strip containing micro-channels, and the resulting mold heating capacity and replication characteristics of the micro-channels are compared with experimental findings in order to verify the validity of the proposed simulation.

Study on the Joining of 2D Microstructure during the Fabrication of 3D Micro-Mold

Bin Xu,Xiao-yu Wu,Jian-guo Lei,Feng Luo,Chen-lin Du,Shuang-chen Ruan,Zhen-long Wang 한국정밀공학회 2014 International Journal of Precision Engineering and Vol. No.

The 3D micro-mold which is fabricated by the femtosecond laser cutting and micro electric resistance slip welding is formed throughthe lamination of multilayer 2D microstructures. By using this technology, the 3D micro-mold with a high depth-width ratio can bemanufactured. In order to improve the laminated precision and joining strength of each layer of 2D microstructure, this researchapplied layer-by-layer micro electric resistance slip welding to weld each layer of 2D microstructure. Firstly, the proper technicalparameters were obtained through the experiments of layer-by-layer micro electric resistance slip welding. Secondly, through thelayer-by-layer micro electric resistance slip welding, multilayer 2D microstructures were weld together and a 3D micro-mold wasformed. Moreover, the anti-shear stress test of 3D micro-mold was done. In the layer-by-layer slip welding process, electrode couldproduce some losses and the losses could deposit on the surface of micro-mold. This research also studied the deposition effect ofthe electrode. Finally, based on the above studies, the micro square-hole array and the micro-gear cavity were fabricated by joiningmultilayer 2D microstructure.

Large volume production of plastic parts with micro-features

Yee-Cheong Lam,Phuong Quoc Mai Nguyen,Khoa Nhat Tran,Xing Chen 한국생산제조학회 2012 한국생산제조시스템학회 학술발표대회 논문집 Vol.2012 No.10

With miniaturization of products with more complex functions integrated, micro-parts have played an ever-increasingly important role in our daily life. This paper presents new developments in micro-injection molding and hot embossing, the two most viable processes for the production of micro-parts. Hot embossing can be used to create the necessary micro-structures not only on polymeric parts, but also on an aluminum alloy mold with controlled quality. A new mechanism of micro-forming, namely the plastic deformation of the polycrystalline AA 6061 grains near the material solidus temperature was reported. It was thus demonstrated that grain size is not the limiting factor on the minimum feature size that could be produced for a polycrystalline material. In the micro-injection molding technique, two main factors, namely melt compressibility and mold surface roughness, were studied. Melt compressibility can be neglected for simplicity in the simulation of macro-injection molding but should be considered in micro-injection mold-filling. Mold surface roughness also has effects on the flow in micro-cavity during the filling stage.

LIGA-like 공정을 이용한 마이크로 부품 복제용 Ni과 Ni-W 금형 제조 및 특성

황완식,박준식,강영철,조진우,박순섭,이인규,강성군,Hwang, W.S.,Park, J.S.,Kang, Y.C.,Cho, J.W.,Park, S.S.,Lee, I.G.,Kang, S.G. 한국재료학회 2003 한국재료학회지 Vol.13 No.1

Electroplated Ni and Ni-W micro-molds using LIGA-like process for replication of micro-components such as microfluidic parts and micro optical parts have been investigated. In general, it is hard to produce micro-parts using conventional mechanical processes. Micro-mold formed by LIGA-like process could fabricate micro-parts with high aspect ratio. In this paper, fabrication and properties of electroplated Ni molds with varying applied current types as well as those of Ni-W molds were investigated. Ni molds fabricated under pulse-reverse current showed the highest hardness value of about 160 Hv. Ni-W molds showed the hardness of about 500 Hv which was much harder than that of Ni electroplated molds. The above results suggested that high quality micro-molds could be fabricated by using Ni electroplating of pulse-reverse type for core molds and sequential Ni-W alloys coating.

Comparison of injection molding and injection/compression molding for the replication of microstructure

홍석관,황정호,강정진,윤경환 한국유변학회 2015 Korea-Australia rheology journal Vol.27 No.4

Because of increasing interest in the functional surfaces including micro- or nano-patterns, the mass production of such surfaces has been actively researched. Both conventional injection molding (CIM) and injection/compression molding (ICM) of micro-patterns were investigated in the present study. The molding subject is a multi-scale structure that consists of a macro-scale thin plate and micro-scale patterns formed regularly on its surface. The transcription ratios of micro pattern made by CIM and ICM for different flow length were experimentally measured, and the origin of the obtained results was identified through numerical analysis. It was found that the cavity pressure and polymer temperature are the most important factors for micro-pattern filling; in particular, the polymer temperature is the key factor determining the transcription ratio. It was also found that the difference in CIM and ICM micro-pattern transcription ratios originates from the differences in the cavity pressure history if other molding conditions are the same

Multi-scale filling simulation of micro-injection molding process

Sung-Joo Choi,김선경 대한기계학회 2011 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.25 No.1

This work proposes a multi-scale simulation method that can simulate filling during the micro-injection molding process. The multiscale simulation is comprised of two steps. In the first step, the macro-scale flow is analyzed using the conventional method. In the second step, the micro-scale simulation is conducted taking the slip and surface tension into consideration to investigate the filling of microcavity. Moreover, a conservative level set method is employed to accurately track the flow front. First, numerical tests have been done for circular micro-channels. The results show that slip and surface tension play important roles in the micro-regime. Second, to verify the multi-scale method, filling of a thin plate with micro-channel patterns has been simulated. The results show that the proposed multi-scale method is promising for micro-injection molding simulations.

Integrated Numerical Analysis to Evaluate Replication Characteristics of Micro Channels in a Locally Heated Mold by Selective Induction

엄혜주,박근 한국정밀공학회 2011 International Journal of Precision Engineering and Vol. No.

High-frequency induction heating is an efficient way to heat mold surfaces by electromagnetic induction using a non-contact procedure. Due to its ability to rapidly heat and cool mold surfaces, this method has been applied recently to the injection molding of micro/nano structures. The present study investigates a localized heating method involving the selective use of mold materials to enhance the heating efficiency of high-frequency induction heating. A composite injection mold consisting of ferromagnetic material and paramagnetic material was used for localized induction heating. The feasibility of this localized heating method was investigated through numerical analyses in terms of its heating efficiency for localized mold surfaces and the resulting flow characteristics in micro channels. To take into account the effects of thermal boundary conditions of localized induction heating, a fully integrated numerical analysis effectively connecting electromagnetic field calculation, heat transfer analysis, and injection molding simulation was carried out. The proposed integrated simulation was applied to the injection molding of a rectangular strip containing micro channels, and the resulting mold heating capacity and replication characteristics of the micro channels were compared with experimental findings in order to verify the validity of the proposed simulation.

미세사출성형에서의 유동성에 대한 실험 및 수치적 연구

이봉기(Bong-Kee Lee),이재구(Jae Gu Lee),권태헌(Tai Hun Kwon) 대한기계학회 2005 대한기계학회 춘추학술대회 Vol.2005 No.5

In this study, the moldability in micro injection molding is investigated both numerically and experimentally. A numerical analysis system, which is based on a domain decomposition of the whole part, has been developed for the injection mold filling of microstructures. Along with the numerical analysis, various injection molding experiments with micro-rib structures are also carried out in order to investigate the moldability in micro injection molding. The melt front advancements in micro-rib structures are measured in detail. Due to a rapid cooling of polymer melt through the thin micro-rib structures, not only the ‘shot shot’ but also the ‘flow back’ phenomena are observed. Furthermore the effects of processing conditions on the moldability in micro-rib structures are also investigated.

Integrated Numerical Analysis to Evaluate Replication Characteristics of Micro Channels in a Locally Heated Mold by Selective Induction

Eom, Hye-Ju,Park, Ke-Un 한국정밀공학회 2011 International Journal of Precision Engineering and Vol.12 No.1

High-frequency induction heating is an efficient way to heat mold surfaces by electromagnetic induction using a non-contact procedure. Due to its ability to rapidly heat and cool mold surfaces, this method has been applied recently to the injection molding of micro/nano structures. The present study investigates a localized heating method involving the selective use of mold materials to enhance the heating efficiency of high-frequency induction heating. A composite injection mold consisting of ferromagnetic material and paramagnetic material was used for localized induction heating. The feasibility of this localized heating method was investigated through numerical analyses in terms of its heating efficiency for localized mold surfaces and the resulting flow characteristics in micro channels. To take into account the effects of thermal boundary conditions of localized induction heating, a fully integrated numerical analysis effectively connecting electromagnetic field calculation, heat transfer analysis, and injection molding simulation was carried out. The proposed integrated simulation was applied to the injection molding of a rectangular strip containing micro channels, and the resulting mold heating capacity and replication characteristics of the micro channels were compared with experimental findings in order to verify the validity of the proposed simulation.