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Because of its high mechanical strength and good comprehensive performance, ABS plastic occupies an important position in the electronics industry, machinery industry, transportation, building materials, toy manufacturing and other industries, especially for slightly larger box structures and stress components.
, The decorative parts that need electroplating are inseparable from this plastic
.
(1) Drying of ABS plastic
ABS plastic has high hygroscopicity and sensitivity to moisture, and sufficient drying and preheating before processing can not only eliminate the firework-like bubbles and silver threads on the surface of the workpiece caused by water vapor, but also help the plasticization of plastics.
to reduce the stain and moiré on the surface of the workpiece
.
The drying conditions before injection molding are: below 75～80℃ in dry winter, drying for 2～3h, and in rainy days in summer, drying at 80～90℃, drying for 4～8h, if the part needs to achieve a particularly good luster or the part itself Complex, the drying time is longer, up to 8 ~ 16h
.
(2) Injection temperature
The relationship between the temperature and melt viscosity of ABS plastic is different from that of other amorphous plastics
.
Therefore, although the injection temperature of ABS is higher than that of plastics such as polystyrene, it cannot have a looser temperature range like the latter
.
The reason is that ABS plastic contains butadiene components.
When a plastic particle is firmly adhered to some surfaces in the screw groove that are not easy to be washed at a higher temperature, and is subjected to a long-term high temperature, it will cause degradation and degradation.
carbonized
.
It is particularly worth mentioning that, due to the high processing temperature of ABS, it is sensitive to changes in various process factors
.
(3) Injection pressure
The viscosity of ABS molten parts is higher than that of polystyrene or modified polystyrene, so a higher injection pressure is used during injection
.
(4) Injection speed
ABS material with medium injection speed effect is better
.
When the injection speed is too fast, the plastic is easy to be scorched or decomposed into gaseous substances, resulting in defects such as weld seams, poor gloss and redness of the plastic near the gate
.
However, when producing thin-walled and complex parts, it is still necessary to ensure a sufficiently high injection speed, otherwise it will be difficult to fill
.
(5) Mold temperature
The molding temperature of ABS is relatively high, and the mold temperature is also relatively high
.
Generally, the mold temperature is adjusted to 75-85°C.
When producing parts with a large projected area, the fixed mold temperature is required to be 70-80°C, and the movable mold temperature is required to be 50-60°C
.
When injecting larger, complex, thin-walled parts, special heating of the mold should be considered
.
In order to shorten the production cycle and maintain the relative stability of the mold temperature, after the parts are taken out, a cold water bath, a hot water bath or other mechanical setting methods can be used to compensate for the original cold fixing time in the cavity
.
(6) Material quantity control
When the general injection molding machine injects ABS plastic, the injection volume per injection is only 75% of the standard injection volume
.
In order to improve the quality and dimensional stability of the parts, the surface gloss and the uniform color tone, the injection volume is required to be 50% of the standard injection volume
.
