三匠實習技術報告與探索陶瓷射出絕緣體製程所引發之表面裂痕缺陷與其成因

本技術報告主要包括兩大部份，第一部份為本人在三匠實習的成果與心得；第二部份為實習過程中針對陶瓷射出絕緣體製程所引發之表面裂痕，萃取出來著重產業技術研究報告。絕緣體廣泛的運用在民生、工業、醫療與軍事等領域，尤其在高電壓之工作環境中，高壓絕緣體更是扮演不可或缺的角色。針對低壓絕緣體一般可應用無機及塑膠材料擔綱製備，然而，高壓絕緣體則是陶瓷絕緣體或合成絕緣體。製作陶瓷絕緣體常利用陶瓷粉末射出成型技術，此方式不僅能大量且穩定滿足消費端的需求，更可利用陶瓷特性達到高壓絕緣的效果。然而在射出成型時，產品表面的裂痕卻是外觀上常見且非常嚴重的缺陷，此項缺陷問題常於脫脂與燒結後之產品觀察到，不過近年來之研究發現此問題可能與生胚(green part)射出成型時的不均勻收縮造成，只是此等產品表面的裂痕與生胚射出成型的具體相關性，至今尚未完整地被掌握。本研究之目的主要想利用數值模擬分析與實驗研究探索高壓絕緣體產品表面的裂痕與生胚射出成型(特別是產品之收縮變化)具體相關性。研究方法與流程，首先利用CAE數值模擬分析方法，針對各項可能之單一因子進行模擬分析，並觀察分析後之體積收縮率結果，找出影響產品體積收縮率變化之最主要因子。其次，以相同條件進行射出成型，觀測數值模擬分析結果體積收縮率較高的位置與生胚缺陷位置的狀況。最後利用數值模擬分析找出最適化參數以解決或改善缺陷問題。另一方面，我們以實際開模進行陶瓷粉末射出成型實驗，欲探討氧化鋁射料在不同的射速、料溫、模溫與保壓壓力之條件下之成型結果，並觀測生胚外觀缺陷上的影響。結果顯示，實際產品射出後，其發生裂痕缺陷的位置與Moldex3D軟體計算預測之結果近乎相同。而從模擬的結果看來，料溫與保壓壓力對體積收縮率分別呈正相關與負相關，當料溫提高，保壓壓力降低，體積收縮率愈大，缺陷發生的機率愈大，程度亦愈嚴重。因此操作條件由料溫160 ℃降至150 ℃，保壓壓力由31 MPa加增至62 MPa，整體體積收縮率有下降的趨勢，且後續實驗驗證也呈現具體之改善。再則，我們也初步建立裂痕缺陷與生胚產品之收縮變化具體定量相關性。

關鍵字

高壓絕緣體；粉末射出成型；生胚；體積收縮率

並列摘要

Insulator has been widely used in our livelihood, industrial, medical and military fields, especially in the working environment of the high-voltage. In general, the high voltage insulator is playing an integral role. The high voltage insulator is often made by the ceramic material. The ceramic insulators generally are manufactured by utilizing ceramic powder injection molding technology, which satisfies a large number of requirements for the consumer. However, during injection molding, some cracks on the surface of the product are common defects in appearance, and those problems are often observed in products after debinding and sintering. However, some recent literatures have proposed that the crack problem might be caused by uneven shrinkage of green parts during injection molding. But the specific correlation between cracks on these surfaces and injection molding of green parts has not been fully understood yet. This study applied both of numerical simulation and experimental studies to explore the specific correlation between cracks on the surface of high-voltage insulators and shrinkage variation after the green parts were injected. Firstly, we have tried to find out the major factors to cause high volume shrinkage region. Then we have proved that the cracks happened regions are matched with that of higher volume shrinkage areas of the green parts numerically. On the other hand, we also performed experimental tests to verify the numerical simulation. Results showed that the real cracks happened regions are matched with that of numerical simulation predicted. Moreover, to overcome the crack problem, the operation conditions have been optimized using CAE (Moldex3D) software. In our real setting, melt temperature is reduced from 160 ℃ to 150 ℃, and packing pressure is increased from 31 MPa to 62 MPa, the crack problem can be totally removed. The correlation between crack problem and the volume shrinkage of the green part is validated.