射出成形參數對頂出力影響之分析

Abstract

近年來隨著科技快速發展，智慧型手機等科技產品已經相當普及，現行的智慧型手機都已經配備照相功能，再加上數位相機、掃描機、望遠鏡與顯微鏡等影像相關產品，光學元件的用量正在逐年提升。而現在有越來越多產品使用塑膠製光學元件，為了使成品有良好的鏡面，並縮短成型所需時間，需要在成品尚未完全固化時開模頂出，此時的頂出力可能使成品損壞。本研究旨在探討射出成形參數的變化對頂出力的影響，試圖找出使頂出力最小化的參數條件，縮短成形時間與提高成品品質。 本研究實際使用射出成形機台進行實驗，以具有導光板形狀之成形品為載具，實驗時量測頂出過程中的頂出力並計算其做功。頂出力由安裝在兩塊頂出板中的荷重計測量，將測得之頂出力波形積分可得到功。 研究結果顯示，頂出力會隨著保壓壓力和保壓時間增加而明顯提升，且保壓時間的影響大於保壓壓力。冷卻時間縮短則頂出力下降，這裡主要是受成品固化程度影響，成品完全固化後頂出力不再變動。 由於光學元件多使用PMMA之類的非結晶性材料，因此頂出力受模溫的影響較小，但在模溫高達90℃時觀察到的頂出力突升則需要進一步分析。而頂出力做功雖然隨著頂出速度增加，但在頂出速度較低時會出現額外的波峰，使得頂出力的趨勢和做功不同，這方面也需要進一步分析。 本研究找出了能夠減少頂出力的參數設定方向，有助於縮短生產時間和提高產品的良率，對於容易在頂出階段損壞的產品具有重要的參考價值。

In recent years, optical components are widely used in smartphones, scanner, telescope, microscope, and other imaging devices. Given the diversity of imaging products, the number of requirements for optical components is increasing annually, and increasingly more products have optical components composed of plastic. To achieve an adequately mirrored surface and shortened manufacturing times, molds must be opened and the component ejected before it solidifies completely. The ejection force at this moment can damage some components. This study investigated the relationship between the ejection force and various injection molding parameters, to identify parameters for minimizing the ejection force, shortening manufacturing times, and improving the quality of products. In this study, we used an injection molding machine and designed a component like light guide plate, to measure the ejection force and the ejection work during manufacturing. The ejection force was measured by a load cell which had been installed between the ejection plates, and determined the ejection work by integrating the waveform of the ejection force. The results show that the ejection force increases with the holding pressure and holding time, and that the holding time has stronger effect compared with the holdind pressure. The ejection force decreases with cooling time. Here, the ejection force is influenced by the curing degree. After the component fully solidified, the ejection force would remain constant. Optical components are typically made from amorphous materials such as PMMA, therefore, the effect of mold temperature on the ejection force is smaller than other parameter’s influence. However, we observed a substantial increase in the ejection force at a mold temperature of 90℃. Although the ejection work increases with the ejection speed, the waveform of ejection force has an extra peak at low ejection speeds. This phenomenon causes that the ejection force has different trend from the ejection work. This study provides setting suggestions which can reduce the ejection force. The suggestion is helpful for shortening manufacturing times and enhancing product yield rate. This study offers crucial insights on fragile components in the ejection phase, such as lenses.