押出模具內分隔島對產品成型強度的影響

The Influence of Mandrel Type in Extrusion Die on Part Strength

鄭文欽(Wen-Chin Cheng)

指導教授 ： 林忠志

國立虎尾科技大學/工程學院/機械與電腦輔助工程系碩士班/碩士(2015年)

https://doi.org/10.6827/NFU.2015.00092

摘要

押出成型為目前廣泛用於製造相同幾何斷面連續長度的成品，生產速度快速且產量高，廣泛被業界使用。本研究探討模具內分隔島機構對聚丙烯(PP)產生分隔作用後再接合的強度，在製造產品這方面使用Brabender Extruder 進行押出成型的實驗，並設計押出機的溫度及轉速，分析不同長度的分隔島其押出成品強度的改變。
為了提升聚丙烯押出成品的穩定度，當聚丙烯由模頭被押出後，立即通過自製的冷卻系統，再經由輸送帶的引導保持生產線的順暢，來維持成品形狀的穩定，參數擷取是利用模頭內安裝的壓力、溫度感測器來偵測材料在模頭內流動的壓力、溫度，在押出成型中塑膠黏度受到溫度、壓力與速度的影響，膠體流動速度是由吐出量去做換算而得到，而吐出量與螺桿轉速有極大的影響，故以溫度、壓力、螺桿轉速此三種數據作為產品穩定性的依據，當在押出成型時，改變模頭內分隔島的長度，比較溫度、壓力與螺桿轉速，對於不同的分隔島長度的影響，最後以拉伸試驗來做抗拉強度的比較，並利用迴歸分析計算出回歸方程式，使得在設計較差的模頭能夠藉由調整溫度、壓力、速度上來達到容許的品質。
實驗結果發現對於產品的接合強度影響最大的因子依序分別為分隔島長度、螺桿轉速、融膠溫度，其中融膠在結合區停留的時間對於接合強度有很大的影響，平均在結合區多停留10%的時間，產品的接合強度可以提升1~6%，尤其在結合區較短的模頭影響較大，實驗發現可以藉由押出機的參數調整使先天接合強度較差的C型模頭，在較低螺桿轉速與高融膠溫度的情況下達到和A型模頭押出成品相同的接合強度。

關鍵字

押出成型 ； 模頭設計 ； 迴歸分析 ； 田口方法

並列摘要

Extrusion method is suitable for the part manufacture with continue section and is a high efficient way mass production. As plastic material is melted and pushed forward pass the die, the part is formed with the cross section of the die continuously. In this study, the extrusion die consisting of different types of mandrels to make the melt be separated and rejoin was designed to simulate the spider leg in conventional die. The weld strength of the molded part is used to investigate the effect of the setting parameters and mandrel type. The plastic material is polypropylene (PP) and Brabender extruder was used for experiment. A pressure sensor and a thermal couple are installed in the die to measure required data for evaluation. The setting parameters for extrusion process are screw rotation speed and melt temperature. The simplified viscosity of the plastic melt can be calculated by the measured data. We use melt temperature, pressure, and screw rotation speed for main control factors to evaluate their influence on the weld strength of the part. The results show that the weld strength made by long mandrel of the die can be improved by increase melt temperature and resident time of the plastic melt. It also shows that the weld strength can increase 1~6% as the resident time of the plastic melt is increased about 10%.

並列關鍵字

extrusion ； die design ； regression analysis

參考文獻

[12]葉怡成，2005，”實驗計劃法-製程與產品最佳化”

[1] John R. Wagner Jr., Eldridge M. Mount III, Harold F. Giles Jr.，2014，”Plastic Behavior in the Extruder”，A volume in Plastics Design Library，Pages 47–70，Pages 105–108

[2] Javier Vera-Sorroche, Adrian Kelly, Elaine Brown, Phil Coates, Nayeem Karnachi, Eileen Harkin-Jones, Kang Li, Jing Deng，2013，”Thermal optimisation of polymer extrusion using in-process monitoring techniques”，Applied Thermal Engineering，Volume 53, Issue 2, Pages 405–413

[3] Guo-Bao Jin, Min-Jie Wang, Dan-Yang Zhao, Hui-Qing Tian, Yi-Fei Jin，2014，”Design and experiments of extrusion die for polypropylene five-lumen micro tube”，Volume214, Issue 1, Pages 50–59

[4] Huiqing Tian, Danyang Zhao, Minjie Wang , Guobao Jin, Yifei Jin，2015，”Study on extrudate swell of polypropylene in double-lumen microprofile extrusion”