Investigation of finite element mesh quality and 3D volume shrinkage compensation method in core and cavity design for optical lenses

• Main Authors: Chia-Hsuan Tsai, 蔡嘉軒
• Other Authors: Zhen-Yuan Zhong
• Format: Others
• Language: zh-TW
• Published: 2019
• Online Access: http://ndltd.ncl.edu.tw/handle/yzu55u

碩士 === 國立中央大學 === 機械工程學系 === 107 === In finite element analysis, mesh generation is an important technique, which directly affects the accuracy and computational efficiency of the simulation. Using BLM (Boundary layer meshes) automatically is fast and easy in Moldex3D, but the mesh quality is not excellent. If using Hexahedron or Prism mesh can greatly improve mesh quality but consuming more time. Therefore, this study generate three kinds of meshes, Prism + Hexa mesh, Mostly Hexa mesh and BLM mesh. To verify the accuracy of model, we compared the results of simulation with experimental melt front and optical retardation. The results of the study shows that the Mostly Hexa mesh can bring the correct molding simulation results. The results of molding simulation of Prism+ Hexa mesh are not so correct. And the results of molding simulation of BLM mesh are incorrect. Then, through the convergence analysis, we generate the different size for Mostly Hexa mesh. By comparing the simulation with the experiment, we found that the mesh size of 0.04 mm can bring the through correct molding simulation results. In order to improve the shape accuracy of optical lenses, industry often use the total volume compensation method to optimize the warpage. However, due to the unequal concentration of the product, it is difficult to meet the requirements of all parts of the product. In this research, we use 3D Volume shrinkage compensation method (3DVSCM) for cavity compensation. In conclusion, using 3DVSCM obviously improves the outer diameter and center thickness of the optical lens.