三維電腦輔助工程於氣體輔助射出成型氣體穿透特性之研究

Study of Gas Penetration Characteristics in Gas-Assisted Injection Molding by Three-Dimensional Computer-Aided Engineering

林鈺婉(Yu-Wan Lin)

指導教授 ： 陳夏宗

中原大學/工學院/機械工程研究所/碩士(2003年)

https://doi.org/10.6840/cycu200300594

摘要

氣體輔助射出成型對於成型品質的改善有許多幫助，但礙於氣體的可控制性差，讓模具設計者望之卻步，雖然商業軟體可提供本製程的成型預測，但是由於其模型經過簡化，對於氣體穿透特性並不能有效而真實的表現，因此三維實體網格的應用實屬必要。以往選擇以簡化的中間平面網格分析，除了可簡化程式複雜度以外，主要是因為計算資源不足。平行處理的出現解決了計算資源的問題，可節省許多計算時間。在本研究中即利用平行處理系統進行氣體輔助射出成型之三維數值計算。
本研究使用有限體積法離散統御方程式，並以流體體積法計算多相流場之波前分佈，同時使用Modified Cross Model和Arrhenius Temperature Equation以建立高分子流體之流變特性。在平板狀成品的模擬研究中，由於實驗中氣針處的氣體射出壓力與系統設定值有所誤差，且數值分析中，以速度設定的計算準確性高於壓力設定，因此以速度估算值作為入射條件。由於本數值方法中氣體為非壓縮流體，且管狀成品的幾何外型設計使得氣體入射時的壓縮效應更加明顯，因此能量轉換使得氣體穿透處溫度上升，而影響其穿透結果的真實性。
研究結果發現三維模擬可有效模擬平板的熔膠流動特性，其遲滯效應與實驗結果近似。對於氣體穿透特性，模擬預測氣體一次穿透長度為113mm與實驗結果相同，氣體穿透之中空率分佈也有相似的結果，但是必須修正氣體的壓縮特性，才能得到更準確的數值結果。

關鍵字

三維 ； 模擬 ； 氣體輔助射出成型

並列摘要

Gas-assisted injection molding is an innovative molding process. Although GAIM can greatly improve product quality, it is difficult to control gas penetration in a desired way. Therefore, mold designers must try and error repeatedly in order to obtain optimal processing conditions. Commercial CAE software can offer solutions to design products better and economically. But gas penetration characteristics are not appeared in 2.5D simulation, so 3D real elements are necessary to be used in simulation of gas-assisted injection molding. In this research, we study gas penetration by 3D simulation and use Cluster Computing system to reduce calculation time.
The application of a finite volume discretization and volume-of-fluid method has been demonstrated to simulate three-dimensional gas-assisted injection molding processes. An effective fluid concept is to compute segregated multi-fluid flows. The modified Cross model and Arrhenius temperature equation are implemented in the numerical scheme in order to describe the rheological properties of polymer flows. Before simulating a plate, gas injection parameter should be set in a right way. So we chose to set gas velocity. In addition, without considering gas compressibility, the simulated result on a spiral part showed that temperature of gas front was so high that polymer becomes melted. And gas penetration slanted seriously. This phenomenon was over and should be corrected.
In this study, 3D simulation results for the plate model were similar to real observation in experiment. The forecast length of gas first penetration was 113mm, almost the same as the experiment.

並列關鍵字

three-dimensional ； simulation ； gas-assisted injection molding

參考文獻

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