In the production of injection molding, the appearance quality of the surface of the injection molded parts, such as matt color, insufficient brightness and insufficient transparency, is often encountered. In addition to the mold cavity surface must first have a good brightness, the main reason for this problem in production is that during the injection process, the melt temperature drops too much, resulting in the melt surface is not enough gloss, Moreover, the fluidity becomes poor, and the contact between the melt and the mold surface is insufficient, so that the shiny mold surface is not faithfully displayed by the injection molded part.
To improve the surface brightness or transparency of injection molded parts, it must be ensured that the melt cannot be cooled too quickly when filling, and must have good fluidity. Therefore, the melt temperature and mold temperature have an important influence on the appearance of injection molded parts.
In fact, properly increasing the melt temperature by more than 10 degrees, and slightly increasing the melt back pressure, the injection should not be too slow, it can indeed improve the effect, but if there is no coordination of the mold temperature, it is more difficult to achieve the ideal Effect.
When the mold temperature is raised above 50 °C (it will feel slightly hot when touched by hand), injection molding ABS, HIPS, PP, PVC and other common plastics can be easily obtained by using the normal melt temperature production Injection molded parts with bright surface or excellent transparency. If the PC material is injected, the mold temperature needs to be higher, preferably above 80 °C.
Therefore, in addition to the melt temperature, the influence of mold temperature on the appearance quality of injection molded parts is also crucial, and the effect is also obvious. It has become an important condition and a common method for solving such problems. The increase of the melt temperature can only be within the limit, too high, it is easy to produce shrinkage, scorching and discoloration.
However, the increase in mold temperature must also have certain limits. The mold temperature rises too high. For example, the mold temperature of hard plastics such as ABS and HIPS exceeds 80 °C (it will feel very hot when touched by hand). When the PC material mold temperature exceeds 120 °C, the injection molded parts are prone to shrinkage and other problems. As a result, the production cycle will become very long.
Conversely, if the injection molded part requires a dull color effect, lowering the melt temperature and mold temperature will also have a certain effect. But the surface of the mold must be sandblasted or etched is the most important prerequisite for ensuring the matte color effect.
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