Ⅰ. ABS Injection Molding Processing Performance
(1) Because of the strong moisture absorption as well as high water content of ABS, the plastic parts that are made of ABS have low gloss and poor internal quality. As a result, ABS injection molding should be dried so that the water content is not more than 0.3%.
(2) ABS melt has obvious non-Newtonian properties. Increasing the molding pressure can significantly reduce the melt viscosity, and its viscosity will also decrease with the increase of temperature.
(3) ABS has a small molding shrinkage rate, and the shrinkage rate changes in the range of 0.3% to 0.8%, so the precision of plastic parts is high.
(4) ABS injection molding has good processing performance, and there are no special requirements for injection molding machines. Both general screw and plunger injection molding machines can be used, but multi-purpose screw injection molding machines have better product quality.
(5) In order to improve the quality, dimensional stability, surface gloss of plastic parts and eliminate residual internal stress when using screw injection mold tooling machine, it is more appropriate to control the injection volume at about 50% of the maximum injection volume.
(6) The viscosity of ABS melt is medium, better than PC and PVC, but worse than PS, so it is better to use straight-through nozzle.
(7) The main channel of the ABS mold is preferably conical, and the main channel should be short, generally about 50mm, and the longest should not exceed 100mm.
(8) The cross-sectional area of the runner must be large enough so that the molten material can fill the cavity before the runner solidifies and compact in the mold. The diameter of the section should generally be greater than 5mm, but not more than 10mm.
(9) The ejection force of the ejection mechanism of ABS should not be too large, otherwise the surface of the plastic part is prone to whitening.
(10) Although the shrinkage rate of ABS injection molding is small, it is easy to generate internal stress, so the plastic parts generally need to be heat treated, and the plastic parts can be treated in hot air at 70 ° C for 2 to 4 hours.
Ⅱ. Conditions for ABS injection molding
(1) Barrel temperature
ABS is an amorphous plastic with no obvious melting point, and the melt flow temperature is not too high. It has sufficient fluidity above 160 °C, but if the temperature is too high, it will not increase the fluidity. There are many varieties of ABS, and the barrel temperature of different varieties is different. The barrel temperature of general ABS is 180~230℃, the temperature of heat-resistant ABS is 190~240℃, and the temperature of flame retardant ABS is 170~220℃. The nozzle temperature is 20~30℃ lower than the barrel temperature.
(2) Mold temperature
The level of mold temperature has a great influence on the quality of plastic parts. During ABS injection molding, the mold temperature should be controlled within the allowable range. Generally, the mold temperature should be controlled at 50-70 °C.
(3) Injection pressure
The size of the injection pressure mainly depends on the structure and wall thickness of the plastic part. Usually, the injection pressure of general ABS is 50-70MPa, the injection pressure of heat-resistant ABS is 60-85MPa, and the injection pressure of flame-retardant ABS is 60-100MPa. If the flow resistance during filling is large, use a higher injection pressure. Conversely, use a lower injection pressure.
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