熱塑性塑膠射出成型模內沖孔製程開發研究

Abstract

本研究利用模內沖孔製程來改善開孔塑膠件之外觀缺陷。由熱塑性塑膠剪斷實驗中探討出剪斷速度以及溫度對於剪斷後之切口尺寸精度以及切口斷面的影響，進而將實驗結果結合射出成型而開發出模內沖孔製程。安裝於塑膠射出成型模具內之剪斷機構，藉由控制剪斷機構的尺寸設計以及塑膠射出成型後的冷卻時間長短，完成一套可應用於開孔塑膠件製作之模內沖孔製程，以改善開孔附近的結合線、應力集中、孔徑收縮以及切口斷面不良之缺陷。�

實驗結果顯示，模內沖孔製程確實可徹底改善結合線缺陷，在ABS與PMMA材料上，可明顯看結合射出成型製程之模內沖孔加工可以消除結合線缺陷，但PC因材料韌性強導致模內沖孔製程無法順利進行。在尺寸精度與切口斷面方面，對於ABS與PMMA材料，剪斷速度越快、冷卻時間越長，其改善效果越佳。

The purpose of this study was to reduce the surface defects of thermoplastic by using in-mold punching process. In the thermoplastic blanking experiment, the punch velocity and the material temperature were selected as the experimental parameters, and their effects on the blanked surface and punched hole dimension were investigated. The experiment results were then incorporated with the injection molding process to form an in-mold punching experiment. The punching device was mounted on the injection mold, several pieces of the plastic plate with holes were injected, the punched surface and hole shrinkage were investigated. The results showed that the in-mold punching could eliminate weld line in ABS and PMMA. However, for PC, the in-mold punching failed to produce a satisfactory hole because of PC’s superior toughness. The in-molding punching process was better than conventional injection molding in reducing hole shrinkage. With the help of the optical magnification, the faster punch velocity and the lower temperature help to produce the better quality of blanked surface.