| Summary: | 碩士 === 中原大學 === 機械工程研究所 === 103 === Gas-assisted injection molding technology(GAIM) a kind of green energy in plastic injection molding, which is injecting gas into the short shot melt in the packing stage. Compressed gas is used as the medium to push melt and maintain pressure. Thus, plastic can be saved effectively to reduce carbon.
Though gas-assisted injection molding has some great improvements in injection quality, compressed gas is still not easy to control preciously, therefore, the final applied products have some defects such as insufficient penetration length, uneven thickness and uneven shrinkage which affects its appearance. Melt flow resistance of gas penetration is the main factor affecting the manufacturing process, and the gas pressure in packing stage would affect the gas penetration. The pressure sensor is installed in the flow pipe, and control the pressure by the adjustable parameters. Gas Counter Pressure (GCP) technology is applied on Forming Injection Molding to control the direction of the bubble size, so as to improve the molding quality.
The study uses the mold core with the shape of paperclip to discuss how the gas counter pressure works in gas-assisted injection molding by melt drag test. Observing how the flow changes by controlling the gas counter pressure and auxiliary gas injection pressure at a constant pressure difference (60bar, 70bar, 80bar and 90bar). And analyzing the relationship between penetration lengths, melt drag flow and molding parameters. This study discussed the effects of counter pressure mechanism on gas-assisted injection molding process and established the database about the mold flow resistance of counter pressure.
Experimental results show that the main factor of counter pressure affecting melt resistance is the viscoelastic behavior of the melt in gas-assisted injection molding. The greater the pressure is, the more melt viscosity became. The proper constant pressure difference helps to inhibit melt flow effect Fountain Flow Effect and helps to produce a hollow. Low constant pressure difference forming product is not easy. Constant pressure difference at high pressures was no significant difference about penetration length, unable to play a benefit.
|
|---|
