熱可塑性樹脂の射出成形における適応制御―型内樹脂圧力変化の解析―
Adaptive Process Control in Injection Molding-Prediction of Cavity Pressure Variation during Pressure Holding Stage-
焼本数利・前川善一郎・_田泰以・酒井忠基
Yakemoto, Kazutoshi / Maekawa, Zenichiro / Hamada, Hiroyuki / Sakai, Tadamoto
As a fundamental to develop a process control system based on the prediction of polymer behavior in a mold cavity, the dynamics of cavity pressure during the pressure holding stage was analysed. Based on the analysis, a new procedure to predict the variation of cavity pressure during the production caused by some kinds of environmental disturbances was proposed.
By using a simplified lumped model, it was analytically shown that the cavity pressure during the pressure holding stage is determined by the polymer flow into the cavity caused by the pressure gradient from the reservoir of the barrel to the cavity, the volumetric shrinkage of the polymer induced by cooling, and the additional polymer flow into the cavity induced by the pressure drop due to the volumetric shrinkage. Furthermore, the relationship between the cavity pressure and its fluctuation causes such as mold temperature, polymer temperature in the barrel and the holding pressure was clarified.
Based on these analytical results, a new procedure to predict cavity pressure variation was proposed and verified experimentally. As a result, a close agreement between measured and calculated cavity pressures was obtained.
In conclusion, it was confirmed that the procedure for prediction presented in this study can be applied effectively to adaptive process control based on the theoretical prediction of polymer behavior in the cavity.
Key words: Injection molding / Process control / Pressure holding stage / Cavity pressure / Fluidity