Effects of Injection Molding Parameters on Ejection Force

• Main Authors: Lin, Yi-Zheng, 林宜正
• Other Authors: Chen, Ren-Haw
• Format: Others
• Language: zh-TW
• Published: 2015
• Online Access: http://ndltd.ncl.edu.tw/handle/91760011438373633805

碩士 === 國立交通大學 === 機械工程系所 === 104 === 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.