The influence of Mold Deflection on the Dimensions and Residual Stresses of Thin-Wall Products

• Main Authors: Shen-Hong Chen, 陳信宏
• Other Authors: Chun-Chin Huang
• Format: Others
• Language: zh-TW
• Published: 2009
• Online Access: http://ndltd.ncl.edu.tw/handle/38141762259198690793

碩士 === 國立高雄應用科技大學 === 模具工程系 === 97 === It needs to raise injection speed and injection pressure when the injection of Thin-Wall part, so the melting high pressure in the mold cavity often causes deflection of mold, it will make the thickness of product outrun the specification, particularly in the Ultra-precision parts, as optical fiber connector, a few micron deflection that may lead to poor quality products. This research with 6 inches of the thickness 1 mm LGP for example, research in injection molding, the mold deflection on the LGP thickness change and the effects of residual stresses, which includes simulation analysis and experiment verification. In the simulation analyzing; first of all to get LGP moldflow analysis at the process of injection molding the cavity pressure, followed by the definition of this pressure distribution into the boundary condition of structure analysis, calculated at this pressure, the mold structure of the deflection situation. In the experiments, the inductive displacement sensor and pressure sensor are mounted into the mold to obtain the mold deflection history and near gate pressure history during the injection molding cycle. After that, the thickness molded LGP part is measured by outside micrometer, that accuracy is 1 m. Residual stress of molded part is checked by photoelasticity. We know that, the MoldFlow software do not consider the mold deformation. Therefore, there is difference between results of the MoldFlow analysis and the results of experiment, when we consider the mold deflection. The difference is very small in case regardless of packing pressure variety, that core plate thickness is 100 mm. Error of the difference is 2  8 m. However, the differences are large in others case, that the core plate thicknesses are sequence of 50 mm, and 35 mm. Finally, the value of mold deformation, which are in all cases, is in large range 30  560 m. Thereafter along with the cooling shrinkage of melting, the pressure in the mold cavity reduces, so that mold deformation gradually reduced, but not zero, Show the product of molding is after solidifying, the core-plate is still the role of compressive stress at plastic part, This compressive stress will result in the plastic products are residual internal stress of one of the reasons why. Keyword: Injection Molding, Mold Deflection, Light Guide Plate, Displacement Sensor, Mould Sensor