三維流動模擬分析在流體輔助射出成型之研究

Three-Dimensional Flow Analysis for the Simulation of Fluid-assisted Injection Molding Process

徐志忠(Chih-Chung Hsu)

指導教授 ： 張榮語

國立清華大學/工學院/化學工程學系/博士(2017年)

摘要

流體輔助射出成型為傳統射出成型帶來突破性之發展，成品內部由於流體掏空，可大幅節省塑膠用料，對塑料及能源成本的降低具有相當顯著的效果。近年來，由於數值方法的成熟及電腦軟硬體技術的提升，使得電腦輔助工程分析在流體射出成型的應用日趨重要。然目前大部分的成型模擬程式都是利用 Hele-Shaw近似法來簡化問題，其主要缺點在於無法預測真正的三維流動現象，以描述出流體輔助成型過程中特有的三維分析現象，如一次和二次滲透、吹穿現象、轉角效應及指紋效應等流體滲透的三維現象。所以，建立一個能真正進行三維模流分析的技術，確有其必要性。
本研究利用利用體心共位式的有限體積法配合 SIMPLER (Semi-Implicit Method for Pressure Linked Equations Revised)去耦合疊代法，達到穩定及快速地求解可壓縮流動統御方程式的目的，並大幅簡化三維計算的複雜性。此外，為了抓取多相界面間成型過程中充填複雜的變化，在固定不變的網格系統下，本研究也建立利用代數體積追蹤法，以高解析界面補捉法 M-CICSAM(Modified-Compressive Interface Capturing Scheme for Arbitrary Meshes)對具有不連續形式的體積分率分程式進行離散及代數求解，從而得到一個鮮明的移動界面位置。
為了驗證本研究方法的正確性，本研究首先檢視所發展出的方法在一般常見的自由面計算例題下的預測性。接著再與文獻上幾何形狀較簡單的模具實驗結果，分析一次和二次滲透及指紋效應等三維流動行為。在這些基礎上，本論文將此三維流動分析技術延伸應用至業界常用的成型製程分析。從分析模擬結果顯示，本研究的三維壓縮流動分析模式確實能正確地預測諸如：複雜幾何下的流體指紋效應、溢流模穴的閥式控制流動行為及塑料倒流法的流體掏空預測。藉由對實際的複雜工業應用案例，進一步驗證本研究方法的正確性及廣泛應用性。

關鍵字

流體輔助射出成型 ； 共位體心有限體積法 ； 高解析界面補捉法 ； 一次及二次流體滲透

並列摘要

Fluid-assisted injection molding (FAIM) process has brought a
breakthrough development for the traditional injection molding industry. The fluid cores out a network of hollow channels throughout the mold cavity to reduce the cost of energy and plastic evidently. In the recent years, the improvements both in the numerical methods and computer hardware have promoted the application of CAE in the modeling of the injection molding process. The major drawbacks of the Hele-Shaw approximation, commonly used today as a means of simplifying the simulation of FAIM process, are the inherent loss of the ability to predict the important physical three-dimensional phenomena for fluid penetration such as blow-out behavior, corner effect, secondary penetration and the finger effect.
This study presents an implicit finite volume approach to simulate the three-dimensional mold filling problems encountered during the injection molding. The described numerical model deals with the three-dimensional non-isothermal flow of incompressible, non-Newtonian fluids with moving interfaces. The collocated finite volume method and the SIMPLER (Semi-Implicit Method for Pressure Linked Equations Revised) segregated algorithm are used to discretize and solve the flow governing equations. All vector or tensor variables are computed in their Cartesian components, and hence no coordinate transformation is required, which considerably simplifies the complicated fully three-dimensional primitive variables flow calculation. In addition, a high resolution interface capturing scheme M-CICSAM (Modified-Compressive Interface Capturing Scheme for Arbitrary Meshes) is adopted to solve the advection equation to capture the sharp interface on a Eulerian framework.
In order to verify the accuracy of this preliminary study, the study first review the predictability of this developed method in the general common free surface and fluid penetration calculation example. Further this study investigates the analysis on relatively simple geometry of three-dimensional mold to study the general 3D phenomena in FAIM process, such as primary and secondary fluid penetration, and fingering effect in order to verify the correctness of the current approach. Moreover, diverse full shot FAIM processes such as overflow and pushback molding process verify mutually with the experimental results on industrial applications. The results show that our novel three-dimensional numerical model is able to predict the complex fluid penetration behaviors in the real mold and the predictions are also consistent with the experimental results to further verify the accuracy of our approach.

並列關鍵字

fluid assisted injection molding process ； collocated finite volume method ； high resolution interface capturing scheme ； primary and secondary fluid penetration

參考文獻

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