氣體輔助射出成型應用於精密鑄造射蠟製程之系統建置與氣體穿透特性之研究

射蠟製程是精密鑄造最初的步驟，若能在此階段對蠟模尺寸有著良好的控制，整體製程的良率和精度就可提高。氣體輔助成型於傳統高分子射出製程中，能達成掏空產品核心肉厚並同時降低收縮與翹曲之功能，提高產品尺寸精度；而將其應用於精密鑄造射蠟製程中是一項技術創新，目前尚未有相關應用特性之探討。因此本論文目的在於建置氣體輔助射出結合精密鑄造射蠟製程之系統以及氣體穿透特性研究。本論文利用具有一維方向的迴紋針模型配合氣體壓力(15、20、25、30bar)、氣體延遲時間(1、2、3s)、氣體持壓時間(10、15、20s)、預充填量(85、90、95%wt.)和料溫(58、61、64oC)對氣體穿透特性進行完整研究，探討其主要穿透長度、二次穿透長度和掏空率並對於傳統製程與氣輔製程產品進行收縮率比較。模流分析部分，首先對蠟材之PVT、黏度、比熱和熱傳導率進行測量，再將測量結果匯入Moldex3D模流軟體中進行充填與氣體穿透長度分析並與實驗比對。實驗結果顯示，氣體於蠟材中穿透過程具有主要穿透與二次穿透現象，其中預充填量對於穿透長度的影響最為明顯；而氣體壓力增加時，掏空率(內徑與外徑比)會隨之增加至逐漸趨緩，其最大掏空率約為0.6565。搭配氣輔製程對尺寸控制的穩定度較佳，收縮率可比傳統的改善約81%，在成品末端未掏空處則改善約25%。當模擬分析傳統射出流動以及氣輔製程的總穿透長度時，分析與實驗結果相符合。本論文藉由氣體穿透特性的研究，證明氣輔製程可成功運用在傳統射蠟製程中，並且同樣對抗收縮率具有良好的效果。

關鍵字

穿透長度；掏空率；射蠟；精密鑄造；氣體輔助成型；收縮率

並列摘要

The wax injection is the initial stage of the investment casting process which is essential to the result of casting such as the quality and accuracy on the product. The gas-assisted injection molding possesses the ability of hollowing the core of product, reducing the shrinkage and warpage so as to enhance the precision on part dimension. Using the gas-assisted technology on the wax injection molding is an innovative molding process. The applications on the wax injection combined with gas-assisted injection molding has no systematic studied yet, therefore, the purpose of this study is to establish the system of gas-assisted wax injection molding and characteristics of gas penetration. In this study, one dimensional spiral tube model was utilized to investigate the characteristics of gas penetration length and hollowed-core ratio under various parameters, gas pressure (15, 20, 25, 30 bar), gas delay time (1, 2, 3s), gas holding time (10, 15, 20s), short shot (85, 90, 95%wt) and wax temperature (58, 61, 64 oC). Moreover, the study compared the shrinkage of the product by using conventional wax injection and gas-assisted wax injection molding. The CAE simulation was also established, the wax properties including viscosity, PVT diagram, heat capacity and thermal conductivity were measured and the results were imported to Moldex3D software. The simulation results of wax filling and gas penetration length were compared with the experiment. The experiment shows gas-assisted technology is successfully applied on wax injection that possesses primary and secondary penetration. According to the experiments, short shot affects the gas penetration length the most. When the gas pressure increases, hollowed-core ratio increases and the highest value of the hollowed-core ratio reaches 0.6565. Shrinkage performance in the gas-assisted wax injection molding improved 81% at primary penetration region and 25% in the end of product. The simulation results of wax filling and gas penetration length have a good agreement with the experiments.

並列關鍵字

Wax Injection ； Gas-Assisted Injection Molding ； Gas Penetration ； Hollowed-Core Ratio ； Shrinkage ； Investment Casting

參考文獻

54. 林鈺婉，“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”，私立中原大學機械工程學研究所碩士論文 (2003)。

47. 黃明忠，“三維電腦輔助工程在模具設計分析應用性之研究”，私立中原大學機械工程學研究所碩士論文 (2002)。

1. T. S. Piwonka, K. A. Woodbury, J.M. Wiest, “Modeling Casting Dimensions: Effect of Wax Rheology and Interfacial Heat Transfer”, Materials and Design, 21, 365-372 (2000).

2. W. Bonilla, S. H. Masood and P. Iovenitti, “An Investigation of Wax Patterns for Accuracy Improvement in Investment Cast Parts”, The International Journal of Advanced Manufacturing Technology, 18, 348-356 (2001).

3. A. S. Sabau, S. Viswanathan, “Material Properties for Predicting Wax Pattern Dimensions in Investment Casting”, Materials Science and Engineering, 362, 125-134 (2003).

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氣體輔助射出成型應用於精密鑄造射蠟製程之系統建置與氣體穿透特性之研究

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