Study on Injection Molding of Intra-oral Scanner Lenses with Shrinkage Compensation

• Main Authors: Sheng-Jhih Huang, 黃聖智
• Other Authors: Min-Wen Wang
• Format: Others
• Language: zh-TW
• Published: 2015
• Online Access: http://ndltd.ncl.edu.tw/handle/ukx7jf

碩士 === 國立高雄應用科技大學 === 機械與精密工程研究所 === 103 === In this study, injection molding process was utilized to manufacture three aspherical lenses of an intra-oral scanner. A shrinkage compensation process was also developed to improve the P-V value of the lenses. There are three optical lenses (lens A, B, and C) in this study, each of them has two aspherical contours and are described as contour I & II. The mold inserts in this study were fabricated by ultra-precision machining which collocated with single crystal diamond tool. At the beginning of this study, we used the mold flow analysis software, Moldex 3D, to assist in both the mold design and determining the initial molding parameters values. Then, the Taguchi Method was carried out to find the optimal parameter combinations for each lens. The last step was shrinkage compensation, first we obtained the lenses contour by Ultrahigh Accurate 3-D Profilometer, then used the MATLAB to assist in calculating the contour differences between molded lenses and designed lenses. The results were used to calculate aspheric coefficient and fitting curve by last square method through MATLAB software for determining the compensated machining equation of the mold insert. Last molding with the compensated mold inserts has been carried out to verify the correctness of this compensation process. The results showed the P-V values of three lenses are effectively reduced after the shrinkage compensation process. The P-V value of Lens A reduced from 8.279 μm down to 0.773 μm; Lens B was 12.464 μm down to 3.981 μm and 1.913 μm down to 0.71 μm, respectively for contours I & II; Lens C was 4.805 μm to 1.112 μm. From the results we know the correctness of this compensation process and it can improve the P-V values of the aspherical lenses.