The Effects of High Shear Rates on Ultra Thin Injection Molding
碩士 === 國立雲林科技大學 === 機械工程系碩士班 === 96 === This study investigates the effect of higher shear rates on the filling patterns, warpage, residual stress and surface gloss for the ultra-thin plates (thickness of 0.4 mm) by thermoplastic micro-injection molding. Both CAE simulation and real experiments were...
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| Format: | Others |
| Language: | zh-TW |
| Published: |
2008
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| Online Access: | http://ndltd.ncl.edu.tw/handle/48r54v |
| Summary: | 碩士 === 國立雲林科技大學 === 機械工程系碩士班 === 96 === This study investigates the effect of higher shear rates on the filling patterns, warpage, residual stress and surface gloss for the ultra-thin plates (thickness of 0.4 mm) by thermoplastic micro-injection molding. Both CAE simulation and real experiments were carried out and compared to each other. Both results reveal that higher injection speed does have different filling pattern when compared to the lower one. Higher injection speed results in higher shear rate and complex temperature distribution. This caused different warpage direction near the gate region. CAE simulation analysis has provided clear information of shear rates, shear stresses and temperature distributions at different injection speeds. And the computer simulation results agree with the experimental data quite well.
The optical scanning system BREUCKMANN 3D was used to measure the warpage of final products. During mold filling, higher shear rate will result in different temperature distribution. And this may cause complex cooling contraction and result in different warp direction when compared to the lower one near the gate region. To measure the residual stresses, a photo-elasticity interferometer was used and we have found flow induced residual stress effects are so significant in this case. The residual stresses are strongly related to the filling patterns at different shear rates. A surface gloss meter was used to measure the surface gloss at different locations of molded plates. Higher shear stress distribution resulting from lower injection speed will lead to lower surface gloss. Higher injection speed makes the material fill into a thinner gap smoother and helps us to obtain higher (better) surface gloss.
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