带有微特征注塑件的复杂流动行为分析
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摘要
随着微机电系统和微／纳米技术的发展,微成型技术得到了快速发展,其中微注塑成型技术成为各国研究的热点之一。由于微注塑成型制品尺寸微小或精度等级高,传统的注塑成型理论及成型工艺不适用于微注塑成型。目前对于微注塑成型理论的还不完善,微注塑成型工艺还需要进一步的探索。
微注塑成型制品可以分为两大类,一类是整个制件本身的尺寸都是微观尺度；一类是宏观尺度的制件上局部带有微观特征。
本文对带有微特征的注塑件进行了充填模拟,重点探讨了微特征入口区域的复杂流动行为。论文主要的工作包括：
1.熔体在微流道入口区域的流动类似于变压力驱动的切变方腔流。通过对宏观制件和微观制件的耦合模拟,我们发现当主流道的速度与流体粘度的比值U/η≥100时,微流道入口区域并不能完全充满,微流道入口区域会有气旋出现,导致制品在微特征区域出现空洞。
2.对带有微特征的注塑件进行结构多尺度模拟,不考虑主流道熔体剪切力对微流道熔体的影响,主要关注微流道的充填长度。通过对注塑件宏观区域的模拟,得到微流道入口处压力的变化历史和熔体温度,并将变压力函数和熔体温度作为边界条件,利用ANSYS CFX对微特征结构的充填过程进行了进一步的数值模拟。详细分析了模具温度、注射速度、微流道入口压力、微流道宽度等工艺和几何因素对微流道充填长度的影响。
3.考虑主流道熔体剪切力对微特征区域的影响,对制件进行宏微观解耦模拟,并对微流道进行准静态方腔流分析。从模拟结果得到,在微流道入口处由于受到X方向和Y方向两个速度的影响下,熔体出现分离的流动,向下充填的同时不断的回旋,出现涡流中心。在主流道速度较大时,涡流中心混杂着空气,主流道速度较小时,涡流中心完全为聚合物熔体。
As the development of MEMS and Micro/Nano technology, the micro forming technology had a rapid development, and the micro injection molding technology has becoming the hot spot of all the countries. Due to products with the micro injection molding have tiny size or highly accuracy level, the traditional injection molding theory and technology shall not be used for micro injection molding. At present the micro injection molding theory is not perfect, and the micro injection molding process methods still need further exploration.
Products of Micro injection molding can be classified into two categories, one kind is the drawing of the size is microscopic scale; The other kind is the macro scale parts with microscopic features.
In this paper we simulated the filling process of injection molding with micro-features, mainly discussed the complex flow behavior in the micro characteristics of entrance areas. The main work includes:
1. The flow in entrance areas of micro channel is similar to variable pressure drive square lumen flow. Through the coupling simulation of the microscopic and microscopic parts, we found that the entrance areas cannot be completely filled whenU/η≥100, there will have a vortex.
2. Based on multi-scale method we simulate the filling length of micro-channel, not considering the influence of melt shear force in macro-channel. Through the filling simulation of the macro area, we get the history of pressure at the entrance micro channel and melt temperature, then taking the variable pressure function and melt temperature as boundary conditions, we simulate the filling process of the micro-channel used ANSYS CFX. We detailed analyze the influence of mould temperature, injection velocity, pressure at inlet region of micro-channel and width of micro-channel to the filling length.
3. We simulate the filling process of micro-channel based on macro and micro decoupling method, considering the influence of melt shear force in macro-channel, and analyze quasi-static square cavity flow. The results show that under the influence of X and Y melt flow directions at the micro-channel inlet region, melt rotate when filling the micro-channel, and then the vortex center appears. If the speed of melt in main channel is bigger, the vortex mingled with air; if the speed is less, vortex is completely full of polymeric melt.
微注塑成型制品可以分为两大类,一类是整个制件本身的尺寸都是微观尺度；一类是宏观尺度的制件上局部带有微观特征。
本文对带有微特征的注塑件进行了充填模拟,重点探讨了微特征入口区域的复杂流动行为。论文主要的工作包括：
1.熔体在微流道入口区域的流动类似于变压力驱动的切变方腔流。通过对宏观制件和微观制件的耦合模拟,我们发现当主流道的速度与流体粘度的比值U/η≥100时,微流道入口区域并不能完全充满,微流道入口区域会有气旋出现,导致制品在微特征区域出现空洞。
2.对带有微特征的注塑件进行结构多尺度模拟,不考虑主流道熔体剪切力对微流道熔体的影响,主要关注微流道的充填长度。通过对注塑件宏观区域的模拟,得到微流道入口处压力的变化历史和熔体温度,并将变压力函数和熔体温度作为边界条件,利用ANSYS CFX对微特征结构的充填过程进行了进一步的数值模拟。详细分析了模具温度、注射速度、微流道入口压力、微流道宽度等工艺和几何因素对微流道充填长度的影响。
3.考虑主流道熔体剪切力对微特征区域的影响,对制件进行宏微观解耦模拟,并对微流道进行准静态方腔流分析。从模拟结果得到,在微流道入口处由于受到X方向和Y方向两个速度的影响下,熔体出现分离的流动,向下充填的同时不断的回旋,出现涡流中心。在主流道速度较大时,涡流中心混杂着空气,主流道速度较小时,涡流中心完全为聚合物熔体。
As the development of MEMS and Micro/Nano technology, the micro forming technology had a rapid development, and the micro injection molding technology has becoming the hot spot of all the countries. Due to products with the micro injection molding have tiny size or highly accuracy level, the traditional injection molding theory and technology shall not be used for micro injection molding. At present the micro injection molding theory is not perfect, and the micro injection molding process methods still need further exploration.
Products of Micro injection molding can be classified into two categories, one kind is the drawing of the size is microscopic scale; The other kind is the macro scale parts with microscopic features.
In this paper we simulated the filling process of injection molding with micro-features, mainly discussed the complex flow behavior in the micro characteristics of entrance areas. The main work includes:
1. The flow in entrance areas of micro channel is similar to variable pressure drive square lumen flow. Through the coupling simulation of the microscopic and microscopic parts, we found that the entrance areas cannot be completely filled whenU/η≥100, there will have a vortex.
2. Based on multi-scale method we simulate the filling length of micro-channel, not considering the influence of melt shear force in macro-channel. Through the filling simulation of the macro area, we get the history of pressure at the entrance micro channel and melt temperature, then taking the variable pressure function and melt temperature as boundary conditions, we simulate the filling process of the micro-channel used ANSYS CFX. We detailed analyze the influence of mould temperature, injection velocity, pressure at inlet region of micro-channel and width of micro-channel to the filling length.
3. We simulate the filling process of micro-channel based on macro and micro decoupling method, considering the influence of melt shear force in macro-channel, and analyze quasi-static square cavity flow. The results show that under the influence of X and Y melt flow directions at the micro-channel inlet region, melt rotate when filling the micro-channel, and then the vortex center appears. If the speed of melt in main channel is bigger, the vortex mingled with air; if the speed is less, vortex is completely full of polymeric melt.
引文
[1]Freemantle M. Downsizing Chemistry[J]. Chem. Eng. News,1999,77(8):27-36
[2]Becker H, Gartner C. Polymer Micro fabrication Methods for Micro fluidic Analytical Applications analytical applications[J]. Electrophoresis,2000,21:12
[3]Weber L, Ehrfeld W. Micromoulding-market position and development[J]. Kunststoffe 1999,89(10): 192-202
[4]Lee L J, Madou M J, Koelling K W. Design and fabrication of CD-like microfluidic platforms for diagnostics: micro fabrication functions[J]. Biomedical Micro devices 2001,3(4), 339-351
[5]Kukla C, Loibl H, Detter H. Micro-injection moulding-the aims of a Project Partnership[J], Kunststoffe plast Europe,1998,88(9):1331-1336
[6]Yao D. Rapid thermal response injection molding for microfabrication[D]. [Ph. D. Thesis]. Amherst, Thesis University of Massachusetts,2001
[7]Harris C, Despa M, Kelly K. Design and fabrication of a cross flow micro heat exchanger[J]. Micro electro mech Syst,2000,9:502-508
[8]Hanemann T, Ulrich H, Ruprecht R. Micromolding of polymer waveguides[J]. Proc SPIE, 1999,3799:225-229
[9]Friedl R W. Injection molding of sub-μm grating optical elements[J]. Injection Molding Technol,2000,4:478-483
[10]Piotter V, Mueller K, Plewa K. Performance and simulation of thermoplastic micro Injection molding[J]. Microsystem Technologies,2002,8(6):387-390
[11]崔志香,刘春太等.带有微结构特征的微注塑过程充填分析[J].郑州大学学报(工学版),2009,30(3)：65-69
[12]YAO D, KIM B. Injection molding high aspect ratio microfeatures[J]. Journal of Injection Molding Technology,2002,6(1):11-17
[13]Shia-ChungChen, Wen-RenJong. Rapid mold temperature variation for assisting the micro injection of high aspect ratio microfeature parts using induction heating technology[J]. Mic-romech Microeng,2006,16:1783-1791
[14]Yao D G, Kim B. Simulation of the filling Process in micro channels for Polymeric materials[J]. MicromeChanics. Microengineering,2002,12(5):604-610
[15]Ya D G, Kim B. Scaling issues in miniaturization of injection molded Parts[J]. Manuf. Sci. Eng,2004,126 (4):733-738
[16]Yu L Y, Lee L J, Koelling K W. Flow and heat transfers simulation of injection molding with microstructures[J]. Polym. Eng. Sci,2004,44(10):1866-1876
[17]Young W B. Simulation of the filling Process in molding components with micro channels Microsystems[J]. Tech,2005,11(66):410-415
[18]Yu L Y, Koh C G, Lee L J. Experimental in vestigation and numerical simulation injection molding with micro-features[J]. Polymer engineer and science,2002,42(5):871-888
[19]Guojun Xu, Li yong Yu, James Lee. Experimental and Numerical Studies of Injection Molding with microfeature [J]. Polymer engineer and science,2005,45:867-875
[20]Tofteberg T R., Andreassen E. Multiscale Simulation of Injection Molding of Parts with Low Aspect Ratio Micro-features[J]. International Polymer Processing,2010,25:63-74
[21]Tofteberg T R, Andreassen E. Simulation of Injection Molding of Micro-featured Polymer Components. SINTEF Materials and Chemistry, Oslo
[22]Papautsky I, Brazzle J, Ameel T A, et al. Microchannel fluid behavior using micropolar fluid theory[J]. Micro Electro Mechanical Systems,1999:544-549
[23]Israelachvili J N. Measurements of the viscosity of thin fluid films between two surfaces with and without adsorbed polymers[J]. Colloid Polymer Science,1986,264:1060-1065
[24]Israelachvili J N. Measurement of the viscosity of liquids In very thin films[J]. Colloid Interface Sci,1986,110:263-271
[25]Forcada M L, Mate C M. The flow of thin viscous-liquid films on rotating-disks[J]. Colloid Interface Sci,1993,169:218-25
[26]Xu B, Ooi K T, Wong T N. Study on the viscosity of the liquid flowing in microgeometry [J]. Micromech,1999,9:337-84
[27]Pozhar L A. Structure and dynamics of nanofluids:theory and simulations to calculate viscosity[J]. Phys. Rev,2000, E61:1422-1446
[28]Papautsky I, Ameel T, Frazier A B. Single-phase fluid flow in microchannels Proc.2nd Int. Symp. Nagoya, Japan. On Advanced Energy Conversion Systems and Related Technologies, 1998,186-187
[29]Hasegawa T, Suganuma M, Watanabe H. Anomaly of excess pressure drops of the flow through very small orifices[J]. Phys. Fluids,1997,9:1-3
[30]Eringen A C, Okada K. A lubrication theory for fluids with microstructure[J]. Eng. Sci. 1995,33:2297-308
[31]庄俭,于同敏,王敏杰等.微注塑成型中熔体充模流动分析及其数值模拟[J].机械工程学报,2008,44(9)：43-49
[32]Berthelot G K. An Introduction to Fluid Dynamites [M]. Cambridge:Cambridge University Press,1970
[33]吴其哗,巫静安.高分子材料流变学[M].北京：高等教育出版社,2002,296-316
[34]Rose Baum EE, Hatzikiriakos S G. Wall slip in the capillary flow of molten polymers subject to viscous heating AICHE[J].1997,43:598-608
[35]Ghoreishy M H R, Razavi-Nouri M, Naderi G. Finite element analysis of flow of thermoplastic elastomeric melt through ax symmetric die with slip boundary condition Plast[J]. Rubber Compos.2000,29:224-228
[36]Kwon T H, Park J B. Finite element analysis modeling of powder injection molding filling process Polym[J]. Eng. Sci.1995,35:741-753
[37]Hwang C J, Kwon T H. Finite element analysis of PIM filling process with slip characterization of powder-binder mixtures[J]. Japan Soc. Powder Metall.1999,46: 837-843
[38]庄俭.微注塑成型充填流动理论与工艺研究[D][硕十学位论文].大连：大连理工大学,2007
[39]Hele-Shaw, H S, Nature. London,1989,58-34
[40]Hieber C. A, Shen S. F. Journal of Non-Newtonian Fluid Mechanics[J].1980,7,1
[41]Kim, B. Injection Molding Microfeatures,NSF Design, Service and Manufacturing Grantees and Research Conference Proceedings,2003,1972-1981
[42]王福军.计算流体动力学分析：CFD软件原理与应用[M].北京：清华大学出版社,2004,19-28
[43]Hirt C W, Nichols B D. Volume of fluid (VOF) method for the dynamics of free boundaries [J]. Comput. Phys,1981,39:210
[44]Kim S W, Turng L S. Three-dimensional numerical simulation of injection molding filling of optical lens and multi-scale geometry using finite element method[J]. Polymer Eng. Sci,2006,46:1263-1274
[45]乔治·埃姆·卡尼亚达克斯,埃里·柏斯考克.微流道-基础与模拟(中国科学院过程工程研究院多相反应重点实验室,多相复杂系统与多尺度方法课题组,译)[M].化学工业出版社,2006：51
[2]Becker H, Gartner C. Polymer Micro fabrication Methods for Micro fluidic Analytical Applications analytical applications[J]. Electrophoresis,2000,21:12
[3]Weber L, Ehrfeld W. Micromoulding-market position and development[J]. Kunststoffe 1999,89(10): 192-202
[4]Lee L J, Madou M J, Koelling K W. Design and fabrication of CD-like microfluidic platforms for diagnostics: micro fabrication functions[J]. Biomedical Micro devices 2001,3(4), 339-351
[5]Kukla C, Loibl H, Detter H. Micro-injection moulding-the aims of a Project Partnership[J], Kunststoffe plast Europe,1998,88(9):1331-1336
[6]Yao D. Rapid thermal response injection molding for microfabrication[D]. [Ph. D. Thesis]. Amherst, Thesis University of Massachusetts,2001
[7]Harris C, Despa M, Kelly K. Design and fabrication of a cross flow micro heat exchanger[J]. Micro electro mech Syst,2000,9:502-508
[8]Hanemann T, Ulrich H, Ruprecht R. Micromolding of polymer waveguides[J]. Proc SPIE, 1999,3799:225-229
[9]Friedl R W. Injection molding of sub-μm grating optical elements[J]. Injection Molding Technol,2000,4:478-483
[10]Piotter V, Mueller K, Plewa K. Performance and simulation of thermoplastic micro Injection molding[J]. Microsystem Technologies,2002,8(6):387-390
[11]崔志香,刘春太等.带有微结构特征的微注塑过程充填分析[J].郑州大学学报(工学版),2009,30(3)：65-69
[12]YAO D, KIM B. Injection molding high aspect ratio microfeatures[J]. Journal of Injection Molding Technology,2002,6(1):11-17
[13]Shia-ChungChen, Wen-RenJong. Rapid mold temperature variation for assisting the micro injection of high aspect ratio microfeature parts using induction heating technology[J]. Mic-romech Microeng,2006,16:1783-1791
[14]Yao D G, Kim B. Simulation of the filling Process in micro channels for Polymeric materials[J]. MicromeChanics. Microengineering,2002,12(5):604-610
[15]Ya D G, Kim B. Scaling issues in miniaturization of injection molded Parts[J]. Manuf. Sci. Eng,2004,126 (4):733-738
[16]Yu L Y, Lee L J, Koelling K W. Flow and heat transfers simulation of injection molding with microstructures[J]. Polym. Eng. Sci,2004,44(10):1866-1876
[17]Young W B. Simulation of the filling Process in molding components with micro channels Microsystems[J]. Tech,2005,11(66):410-415
[18]Yu L Y, Koh C G, Lee L J. Experimental in vestigation and numerical simulation injection molding with micro-features[J]. Polymer engineer and science,2002,42(5):871-888
[19]Guojun Xu, Li yong Yu, James Lee. Experimental and Numerical Studies of Injection Molding with microfeature [J]. Polymer engineer and science,2005,45:867-875
[20]Tofteberg T R., Andreassen E. Multiscale Simulation of Injection Molding of Parts with Low Aspect Ratio Micro-features[J]. International Polymer Processing,2010,25:63-74
[21]Tofteberg T R, Andreassen E. Simulation of Injection Molding of Micro-featured Polymer Components. SINTEF Materials and Chemistry, Oslo
[22]Papautsky I, Brazzle J, Ameel T A, et al. Microchannel fluid behavior using micropolar fluid theory[J]. Micro Electro Mechanical Systems,1999:544-549
[23]Israelachvili J N. Measurements of the viscosity of thin fluid films between two surfaces with and without adsorbed polymers[J]. Colloid Polymer Science,1986,264:1060-1065
[24]Israelachvili J N. Measurement of the viscosity of liquids In very thin films[J]. Colloid Interface Sci,1986,110:263-271
[25]Forcada M L, Mate C M. The flow of thin viscous-liquid films on rotating-disks[J]. Colloid Interface Sci,1993,169:218-25
[26]Xu B, Ooi K T, Wong T N. Study on the viscosity of the liquid flowing in microgeometry [J]. Micromech,1999,9:337-84
[27]Pozhar L A. Structure and dynamics of nanofluids:theory and simulations to calculate viscosity[J]. Phys. Rev,2000, E61:1422-1446
[28]Papautsky I, Ameel T, Frazier A B. Single-phase fluid flow in microchannels Proc.2nd Int. Symp. Nagoya, Japan. On Advanced Energy Conversion Systems and Related Technologies, 1998,186-187
[29]Hasegawa T, Suganuma M, Watanabe H. Anomaly of excess pressure drops of the flow through very small orifices[J]. Phys. Fluids,1997,9:1-3
[30]Eringen A C, Okada K. A lubrication theory for fluids with microstructure[J]. Eng. Sci. 1995,33:2297-308
[31]庄俭,于同敏,王敏杰等.微注塑成型中熔体充模流动分析及其数值模拟[J].机械工程学报,2008,44(9)：43-49
[32]Berthelot G K. An Introduction to Fluid Dynamites [M]. Cambridge:Cambridge University Press,1970
[33]吴其哗,巫静安.高分子材料流变学[M].北京：高等教育出版社,2002,296-316
[34]Rose Baum EE, Hatzikiriakos S G. Wall slip in the capillary flow of molten polymers subject to viscous heating AICHE[J].1997,43:598-608
[35]Ghoreishy M H R, Razavi-Nouri M, Naderi G. Finite element analysis of flow of thermoplastic elastomeric melt through ax symmetric die with slip boundary condition Plast[J]. Rubber Compos.2000,29:224-228
[36]Kwon T H, Park J B. Finite element analysis modeling of powder injection molding filling process Polym[J]. Eng. Sci.1995,35:741-753
[37]Hwang C J, Kwon T H. Finite element analysis of PIM filling process with slip characterization of powder-binder mixtures[J]. Japan Soc. Powder Metall.1999,46: 837-843
[38]庄俭.微注塑成型充填流动理论与工艺研究[D][硕十学位论文].大连：大连理工大学,2007
[39]Hele-Shaw, H S, Nature. London,1989,58-34
[40]Hieber C. A, Shen S. F. Journal of Non-Newtonian Fluid Mechanics[J].1980,7,1
[41]Kim, B. Injection Molding Microfeatures,NSF Design, Service and Manufacturing Grantees and Research Conference Proceedings,2003,1972-1981
[42]王福军.计算流体动力学分析：CFD软件原理与应用[M].北京：清华大学出版社,2004,19-28
[43]Hirt C W, Nichols B D. Volume of fluid (VOF) method for the dynamics of free boundaries [J]. Comput. Phys,1981,39:210
[44]Kim S W, Turng L S. Three-dimensional numerical simulation of injection molding filling of optical lens and multi-scale geometry using finite element method[J]. Polymer Eng. Sci,2006,46:1263-1274
[45]乔治·埃姆·卡尼亚达克斯,埃里·柏斯考克.微流道-基础与模拟(中国科学院过程工程研究院多相反应重点实验室,多相复杂系统与多尺度方法课题组,译)[M].化学工业出版社,2006：51