Factors and solutions that affect the surface brightness of injection molded parts
Aug 18, 2021
Factors and solutions that affect the surface brightness of injection molded parts
Brightness factor of injection molded parts
We often encounter the appearance quality problems of the surface of injection molded parts such as dull color, insufficient brightness and insufficient transparency.
Except that the surface of the mold cavity must first be guaranteed to have good brightness, the main reason for this problem in production is that the temperature of the melt drops too much during the injection process, which makes the surface of the melt not shiny enough, and The fluidity becomes worse, and the contact between the melt and the mold surface is not adequate enough, so that the bright mold surface is not faithfully displayed by the injection molded part.
To improve the surface brightness or transparency of injection molded parts, it is necessary to ensure that the melt cannot be cooled too fast when filling the mold, and it must have good fluidity. Therefore, the melt temperature and mold temperature have a significant impact on the appearance of injection molded parts.
In fact, appropriately increasing the melt temperature by more than ten degrees, and slightly increasing the back pressure of the melt, do not shoot the glue too slowly, it can indeed play a better role, but if there is no matching of the mold temperature, it will be more difficult to achieve Desired effect
When we raise the mold temperature to above 50 degrees (touching the mold with your hands will feel a little hot), injection molding ABS, HIPS, PP, PVC and other commonly used plastics, just use the normal melt temperature to produce, it can be very easy To obtain an injection molded part with a bright surface or excellent transparency. If it is injection molding PC material, the mold temperature needs to be higher, preferably above 80 degrees.
Therefore, in addition to the melt temperature, the influence of the mold temperature on the appearance quality of the injection molded parts is also very important, and the effect is also obvious. It has become an important condition and common method to solve such problems. The increase of the melt temperature can only be moderate, and if it is too high, it is easy to cause problems such as shrinkage, burning and discoloration.
However, the increase in mold temperature also has a certain limit. The mold temperature rises too high. For example, the mold temperature of hard rubber such as ABS and HIPS exceeds 80 degrees (it will feel very hot when touched by hand). When the mold temperature of PC material exceeds 120 ℃, the injection molded parts are prone to shrinkage and other problems. , The production cycle will therefore become too long.
On the contrary, if the injection molded parts need a matte effect, lowering the melt temperature and mold temperature will also have a certain effect. However, the mold surface must be sandblasted or etched, which is the most important prerequisite to ensure the matte effect.
