模內動態壓力對塑膠射出件之研究

Cavity Dynamic Pressure on the Injection Molding Plastic Parts

10.6841/NTUT.2010.00019

張政雄

收縮變形 ； 模內壓力變化曲線 ； 模內壓力波形 ； 壓電式壓力感測器 ； 射出成型循環 ； 動態壓力 ； shrinking deformation ； cavity pressure change curve ； cavity pressure profile ； piezoelectric pressure sensors ； injection molding cycle ； dynamic pressure

臺北科技大學製造科技研究所學位論文

2010年

碩士

韓麗龍

繁體中文

3C產品大都是由兩個以上的塑膠零件組裝而成，如：電腦、通訊設備、消費電子等。若塑膠零件在射出成型過程有過大的收縮變形時，將影響產品的組裝與外觀；雖然影響塑膠成型件的因素很多，然而模內壓力變化對成品收縮變形扮演著關鍵性的角色。在射出成型的每個階段(充填、熔膠加壓、保壓、冷卻)都會反映出不一樣的模內壓力，由不同的射出成型條件，即可得到不同的模內壓力變化曲線(cavity pressure change curve)，或稱為模內壓力波形(cavity pressure profile)。 本研究是把壓電式壓力感測器安裝在模穴中，利用感測器量測在整個射出成型循環過程中模內的動態壓力變化，且進一步獲得模內壓力波形與收縮變形之間的對應關係。研究結果顯示射出壓力、熔膠溫度、模具溫度是影響模內壓力的主要因素。其中以射出壓力影響最大，其次是熔膠溫度模具溫度影響較小。另一方面隨著熔膠的冷卻收縮，模內的壓力降低但無法歸零，這是因為成型品固化後模具壓縮應力仍作用在成型品上。

3C products are assembled by more than two of plastic parts, such as computers, communication devices, and electronic consumers, etc. If an over-large shrinking deformation exists in the plastic part, it will affect the product assembly and aesthetics. Although many factors affect on the injection molding condition, the change of cavity pressure just plays a key role on the plastic parts shrinking deformation. Injection molding is a cyclic process consisting of filling, melt compressing, holding, and cooling. The different pressures reflected on each stage, and the optimized injection molding conditions obtained according to the cavity pressure change curve, also called cavity pressure profile. In this study, we used piezoelectric pressure sensors installing into the mold to measure the dynamic pressure change of cavity during injection molding cycle. Moreover, we also obtain relationship between the cavity pressure profile and shrinking deformation. The experimental results show that injection pressure, molten temperature and mold temperature are main factors to influence on cavity pressure. Among them, injection pressure is the most influenced factor, molten temperatures is the second one, and then mold temperature with less impact. On the other hand, with melt cooling shrinkage, cavity pressure is reduced but not down to zero. It is because that after solidifying, the mold compressive stress is still at plastic part.

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