Six conditions of ABS plastic injection molding
Six conditions of ABS plastic injection molding
ABS resin is a tripolymer that is developed based on the modification of polystyrene resin. Where A stands for propylene, B for butadiene, S for styrene. ABS has three kinds of comprehensive properties, A can improve oil resistance and chemical corrosion, so it has certain surface hardness. B gives ABS a rubbery toughness and improves impact toughness; S makes ABS plastics exhibit better fluidity, so that it has the good performance of thermoplastic forming process.
Horizontal injection molding machine
ABS plastic is mainly used in our country to manufacture instrument and instrument, household appliances, telephone, TV and other shell and electroplated ABS plastic, so that it can be used to replace metal. Injection molding is the main form of ABS plastic, its forming mainly depends on six conditions.
Drying of ABS plastic ABS plastic the hygroscopicity and moisture sensitivity is bigger, to fully dry and preheating before machining, not only can eliminate surface shape of fireworks caused by water vapor bubble belt, silver, but also help plastic plasticizing, reduce surface discoloration and moire. ABS materials should control moisture under 013 %.
Injection before drying condition is: dry winter day in 75 ~ 80 ℃ below, 2 ~ 3 h, dry summer rain days under 80 ~ 90 ℃, 4 ~ 8 h dry, such as parts to achieve special excellent gloss or itself complex parts, the drying time is longer, up to 8 to 16 h. The presence of water vapor caused the surface fog to be an overlooked problem.
The injection temperature
The relationship between the temperature of ABS plastic and the melt viscosity is different from that of other amorphous plastics. At higher temperatures the melting process, the molten actually reduce is very small, but once the plasticizing temperature (temperature range is suitable for processing, such as 220 ~ 250 ℃), if it continues to heat up, blindly without too much will cause the heat resistance of thermal degradation of ABS makes melt viscosity increases, injection more difficult, also fell on the mechanical properties of the parts. Therefore, ABS injection temperature is higher than that of polystyrene and other plastics, but it cannot be as easy to warm up as the latter.
The greater the temperature change, it will bring the defects such as weld seam, poor gloss, flying side, mould and color.
Injection pressure
The viscosity of ABS melt is higher than that of polystyrene or modified polystyrene, so high injection pressure is used in injection. Of course, not all ABS components should be applied with high pressure. Small, simple and large parts can be used with lower injection pressure. In the process of injection, the pressure size in the closed moment cavity of the gate determines the surface quality of the parts and the degree of the silver filiform defect. The pressure is too small, the plastic shrinkage is large, and the surface of the cavity is free of contact, the surface is atomized. The pressure is too high. The friction between plastic and the cavity surface is strong, and it is easy to cause adhesion.
Injection speed
ABS is good for medium injection speed. When the injection rate is too fast, the plastic can be scorched or decomposed into the gasification material, thus causing defects such as weld seam, gloss difference and plastic redness near the gate. However, in the production of thin-wall and complex parts, it is necessary to ensure that there is sufficient injection speed, otherwise it will be difficult to fill.
Mold temperature
Injection mold
ABS has relatively high forming temperature and relatively high mold temperature. Generally adjust the mold temperature is 75 ~ 85 ℃, when the production has a large projection area of parts, mold temperature requirements of 70 ~ 80 ℃, 50 ~ 60 ℃ dynamic mold temperature requirements. In the case of large, complex and thin-walled parts, special treatment for mold heating should be considered. In order to shorten the production cycle, maintain the mold temperature is relatively stable, after take out the parts, can use cold water, hot water bath or other mechanical finalize the design method to compensate for the original cold type fixed time within the cavity.
Feed rate control
In general injection molding machine injection ABS plastic, the injection amount is only 75% of the standard injection amount. In order to improve the quality and size of the product, the surface gloss and the uniform of the tone, the injection amount is 50%.
