（43） Defects in transparent parts Injection Molding Process Defect Handling Manual (65 types)

Transparent products such as molten spots, silver stripes, cracked polystyrene, and plexiglass can sometimes be seen through the light to see some shiny, filigree like silver stripes.
These silver markings are also known as speckles or cracks. This is due to the stress generated in the vertical direction of the tensile stress, which is manifested by the difference in the refractive index between the weight flow orientation of the polymer molecules and the non oriented portion.
resolvent:
(1) Eliminate the interference of gases and other impurities, and fully dry the plastic.
(2) Reduce the material temperature, adjust the temperature of the material barrel in sections, and appropriately increase the mold temperature.
(3) Increase injection pressure and decrease injection speed.
(4) Increase or decrease the pre molding back pressure and reduce the screw speed.
(5) Improve flow path and cavity exhaust conditions.
(6) Clean possible clogging of nozzles, runners, and gates.
(7) Shorten the molding cycle, and after demolding, annealing can be used to eliminate crazing: for polystyrene, maintain it for 15 minutes at 78 ℃, or maintain it for 1 hour at 50 ℃, and for polycarbonate, heat it to above 160 ℃ and maintain it for several minutes.