Common problems and solutions in transparent plastic injection molding
by：Vowin Rapid Prototyping2023-02-06
Common transparent materials include PMMA, PC, PS, acrylic, etc. Transparent materials will also encounter many problems in the process of injection molding, such as silver streaks, air bubbles, etc. Today, Wo Neng Precision’s engineers will summarize for you The common problems and solutions of transparent parts are as follows:
(1) Silver streaks: due to the influence of internal stress anisotropy during the filling and condensation process, the stress generated in the vertical direction causes the resin to have a flow-up orientation, and the refractive index is different from that of the non-flow orientation, resulting in shiny silk lines. When it expands, it may crack the product.
Solution: Clear magazines, pollutants, fully dry raw materials, control melt temperature, increase injection pressure appropriately, exhaust air reasonably, and pay attention to nozzle blockage.
(2) Bubbles: Mainly because the water vapor and other gases in the resin cannot be discharged. During the condensation process of the mold or due to insufficient mold filling, the condensation surface condenses too quickly to form 'vacuum bubbles'.
Solution: The raw material is fully dry, appropriately increase the injection time, speed and injection pressure, control the mold temperature, and pay attention to nozzle blockage.
(3) Poor surface gloss: mainly due to the large roughness of the mold, on the other hand, the condensation is too early, so that the resin cannot copy the state of the mold surface, all of which make the surface produce small unevenness and make the product lose its luster.
Solution: Properly increase the melt temperature, injection pressure, injection speed and injection time, increase the mold temperature and cooling time.
(4) Vibration lines: refers to the dense corrugations formed from the sprue as the center. The reason is that the front-end material has condensed in the cavity due to the excessive viscosity of the melt, and the later material breaks through the condensation surface, resulting in vibration lines on the surface .
Solution: increase the temperature at the melt nozzle, injection pressure, injection speed and injection time, and improve the exhaust of the cooling well.
(5) Whitening, halo: mainly caused by dust falling into the raw material in the air or the raw material has too much water content.
Solution: Clear magazines, pollutants, fully dry raw materials, control melting temperature, and shorten production cycle.
(6) White smoke, black spots: mainly due to the decomposition or deterioration of the resin in the barrel due to local overheating of the plastic in the barrel.
Solution: Clear magazines and pollutants, reduce the temperature of the material, and reduce the residence time of the material in the barrel.