模具快速冷卻系統建置應用於超臨界微細發泡品質控制之研究

Study on Establishment of Mold Fast Cooling System and Its Application to Control Foaming Quality in Microcellular Injection Molding Process

曾家彥(Chia-Yen Tseng)

指導教授 ： 陳夏宗

中原大學/工學院/機械工程研究所/博士(2012年)

https://doi.org/10.6840/cycu201200121

摘要

溫度的控制直接影響射出成型產品的品質與生產週期，理想的模具加熱與冷卻技術可同時提高產品精度與外觀等優點並縮短成型週期。為達成快速加熱的目的，各類模面式或模內式加熱有諸多完整高效的發展，而高效均勻的冷卻技術開發仍顯不足；高模溫應用於超臨界流體微細發泡射出成型(Microcellular Injection Molding, MuCell®)可有效改善表面缺陷，但由於冷卻效率不足產生內部巨型氣泡與均勻度低等問題，因此快速均勻的冷卻系統設計為達成高溫製程需求與有效控制產品品質的重要關鍵。
本研究對高熱傳導材料(QC-10)、高硬度鋼(M333)與兩種材料組合的複合式模具設計(Complex)進行冷卻效率研究，利用分析軟體CFDRC®進行溫度場分析與驗證，並探討在不同材料、冷卻液溫度與厚度比組合下之冷卻效率並建立設計準則。MuCell®高模溫成型實驗利用所建置的快速冷卻系統搭配氣體反壓技術(Gas Counter Pressure, GCP)以控制發泡品質。
研究結果顯示，冷卻效率以M333 < Complex < QC-10，速度最快可達10 °C/sec以上，分析模擬與實驗結果趨勢相當接近，其中複合式模具提供更ㄧ致的冷卻速度與溫度均勻度，並提供更彈性的水路空間配置以及設計自由度。MuCell®設定模溫120 °C與搭配冷卻速度控制1.1、5.1、10.9 °C/sec成型時，氣泡尺寸可由192.92 µm縮小至84.97 µm；搭配GCP 100 bar與持壓時間5秒時氣泡尺寸由73.68 µm縮小至38.85 µm，隨著冷卻速度與GCP時間增加發泡尺寸越均勻。冷卻速度與GCP時間增加將提高皮層厚度與降低發泡密度；由於氣體壓力移除後發泡行為即不受控制，因此延長洩壓時間可提高氣泡均勻度並縮小氣泡尺寸與增加皮層厚度。快速冷卻搭配GCP應用可大幅提升超臨界微細發泡品質。

關鍵字

氣體反壓技術 ； 快速冷卻 ； 超臨界微細發泡成型

並列摘要

Mold temperature affects part quality and cycle time in injection molding processes obviously. Ideal heating and cooling technologies are used to improve not only the surface performance but also shorten the cycle time. There is much literature for mold heating methods, but little research pertaining to efficient and uniform cooling technology. In microcellular injection molding (MuCell®), high mold temperatures provide great contributions to improve the surface defects, however cause large bubble sizes and low uniformity. Therefore, a fast and uniform cooling system was required.
In this work, the methods and principles of mold and material design for cooling systems were discussed, and then several different kinds of correlative parameters were designed. The cooling speed and temperature uniformity of mold were simulated. Further, fast cooling system and gas counter pressure (GCP) technology were used to control foaming qualities in the MuCell process.
As for the results, the cooling efficiency is M333 < Complex < QC-10, the fastest cooling speed is more than 10 °C/sec, with analytical results matching results from the experiment. The complex mold design achieves more uniform cooling efficiency and flexible cooling channel design. In MuCell® experiments, various cooling speeds and mold temperatures were set. As for the fastest cooling speed (10.9 °C/sec, 120°C), the cell size decreased from 192.92 µm to 84.97 µm furthermore the addition of 100 bar GCP with 5 sec holding decreased the cell size from 73.68 µm to 38.85 µm. Faster cooling speed and longer GCP holding time increases skin thickness and lowers cell density. As the GCP releases, the foam behavior tends to be uncontrollable. Extending gas relief time can increase cell uniformity as well as decrease skin thickness and cell size. Combined fast cooling and GCP control improves foam quality efficiently.

並列關鍵字

Fast cooling ； Gas counter pressure ； Microcellular injection molding

參考文獻

18. 楊哲瑋，“氣體輔助加熱搭配模具設計應用於模具表面加熱效益改善之研究”，私立中原大學碩士論文，2008。

30. 江志良，“動態模溫控制模擬驗證之研究”，私立中原大學碩士論文，2004。

71. 許評順，“模內氣體反壓與動態模溫機制應用於超臨界微細發泡射出成型發泡控制與表面品質影響之研究”，私立中原大學博士論文，2011。

72. 蕭宇倫，“模內氣體反壓與動態模溫協同控制系統應用於超臨界微細發泡射出成型發泡控制及產品機械性質之研究”，私立中原大學碩士論文，2011。

2. Z. Chen and L. S. Turng, “A Review of Current Developments in Process and Quality Control for Injection Molding”, Advances in Polymer Technology, 24, 165-182, 2005.