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Shrinkage in Injection Molded Part for Operational Conditions and Resins  

Mo, Jung-Hyuk (Dept. of Precision Mechnnical Engineering, Seoul National Univ. of Technology)
Chung, Wan-Jin (Dept. of Die & Mould Design, Institute of Precision Machinery Technology, Seoul National Univ. of Technology)
Lyu, Min-Young (Dept. of Die & Mould Design, Institute of Precision Machinery Technology, Seoul National Univ. of Technology)
Publication Information
Elastomers and Composites / v.38, no.4, 2003 , pp. 295-302 More about this Journal
Abstract
The amount of shrinkage of injection molded parts is different from operational conditions of injection molding such as injection temperature, injection pressure and mold temperature, and mold design such as gate size. It also varies depending on the presence of crystalline structure in resins. In this study, part shrinkage was investigated for various operational conditions and resins. Poly(butylene terephthalate) (PBT) for crystalline polymer, and polycarbonate (PC) and poly(methyl methacrylate) (PMMA) for amorphous polymers were used. Crystall me polymer showed higher part shrinkage by about three times than that of amorphous polymers. Part shrinkage increased as melt and molt temperatures increased, and injection pressure decreased. Part shrinkage decreased as gate size increased since the pressure delivery is mush easier for larger gate sizes. Part shrinkage at the position close to the gate was larger than that or the position far from gate. This phenomenon might be occur by difference of residual stress.
Keywords
injection molding; part shrinkage; injection temperature; mold temperature; injection pressure;
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