| Gas assisted injection molding (GAIM) offers many advantages over the conventional injection molding wherein hollow parts are produced with the help of the nitrogen which provides superior surface finish, reduced part weight and shorter cycle time. To achieve a successful GAIM process, it is essential to understand the nature of GAIM process. However, many aspects of GAIM have yet to be explored.; The objective of this study is to understand the causes of fingering in GAIM process which, in turn, causes premature failure of a part. A computer based pressure controlled GAIM control unit was developed. A three layer L{dollar}sb{lcub}18{rcub}{dollar} and a two layer L{dollar}sb8{dollar} DOE via Taguchi methods were used to study the effect of processing parameters. Six processing variables were investigated. They are melt temperature, mold temperature, shot size, injection speed, gas pressure and gas delay time were studied. Full factorial computer simulations were also performed.; Shot size shows the most significant effect on fingering and gas penetration. The fingering area decreased as the mold temperature increased, and as the delay time increased. Melt temperature, gas pressure, and delay time are suitable for trouble shooting since they show same trend for increasing gas bubble penetration and decreasing fingering area. The significance of processing variables varied from experiment to experiment. However, for most cases, gas pressure and injection speed showed only a small effect on fingering. Fluidity ratios between 40 to 100 showed the least fingering. |
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