Injection Molding Accuracy Control of Lenses Using In-Mold Compression

• Main Authors: Huang, Po-Yu, 黃柏毓
• Other Authors: Chen, Ren-Haw
• Format: Others
• Language: zh-TW
• Published: 2019
• Online Access: http://ndltd.ncl.edu.tw/handle/2tt9ba

碩士 === 國立交通大學 === 機械工程系所 === 107 === With the rapid development of smart phone, the lenses of mobile phone are increasingly refined in imaging and miniaturized in sizes; as a result, lens formation becomes more difficult than ever. Since the thinness and small size of lenses, multi-cavity molds would generally be used for mass production. In the rapid production of multi-cavity mold, individual quality is more difficult to control, and poor quality will also cause the cost increase for manufacturers. Injection-compression molding (ICM) process can lower the warpage deformation and internal stress than the injection molding (IM), as well as yielded finished products with better quality. However, in the compression stage of ICM, the whole mold is compressed by the ejector mechanism, thus it is difficult to control individually quality for multi-cavity product. Therefore, this study attempted to use the compression mechanism to control the pressure of the single cavity in the cooling stage, it is expected to improve the accuracy of individual lenses. In this study, the in-mold compression(IMC) method was used, as well as the servo motor to drive the screw to move the cavity insert in order to pressurize the cavity material after the packing stage. The load cell set up between the cavity insert and the screw to feed back the compressive load to the computer in order to control this closed-loop compression force. The results showed that the in-mold compression can reduce the shrinkage rate of maximum height of profile from 3.46 % of IM to 2.90 % of IMC. It is helpful to improve the profile accuracy of the lenses. In terms of shrinkage rate of diameter, there is no difference between these two processes. As for the shrinkage rate of thickness, the gate of these two processes is better than the flow-end, and for the in-mold compression, when the compression force is become larger, the flow-end of lenses will be thinner than the gate. With adopting the in-mold compression method in this study, the shrinkage rate of profile can be reduced, and the focal length of the lens would be close to the original design as possible, and the imaging quality will be greatly improved as well.