Study on minimizing warpage of injection molding for desktop plastic case

• Main Authors: Huang chih wei, 黃智維
• Other Authors: Huang chung ching
• Format: Others
• Language: zh-TW
• Published: 2011
• Online Access: http://ndltd.ncl.edu.tw/handle/33445751162779080801

碩士 === 國立高雄應用科技大學 === 模具工程系 === 99 === The warpage of desktop computer case is not only caused by thin-wall injection and complex structures, but also the uneven thickness. Short-shot is caused by high flow ratio, however residual stress of high pressure also leads warpage. This research is focus on case of desktop computer which is with average thickness 2.5mm, length 510mm, width 210mm,height 38mm. To select engineering plastic ABS as the material for the consideration of high flow ratio and sufficient impact feature. This product surface is fine finishing which requires high mold temperature and high injection speed at molding. The above injection conditions often cause high shrinkage and residual stress which defect the warpage. This study utilizes Moldflow to simulate the injection status of computer case which adopts different gate locations to minimize warpage and optimize injection parameters. The Moldflow simulation is verified afterwards through the optimized parameters at molding trail. The purpose of this study is to build a development mode to reduce the cost both of human and material at similar development. This study concludes in following four points: (1) Analysis result of warpage is greatly reduced by gate improvement according to references rather than experienced methods. (2) Planning and analysis by Taguchi method calculated the most important injection parameter which affect warpage of different gates are in order of melt temperature and holding pressure. (3) The most contributed factor of warpage is melt temperature. (4) Trail experiment verifies that the optimum factor calculated by Taguchi method results in minimum warpage.