Injection molding technology is a commonly used production method of plastic products. Many types of plastic products are produced by plastic products factories using injection molding machines. Like mobile phone cases that are very popular in our lives are one of them. However, many injection mold manufacturers with insufficient technology often have some shiny silver lines when they use TPU, PC and other materials to make transparent products, which greatly affects the aesthetics of the product.
What is the cause of the problem?
In fact, the quality defects such as melt marks, silver streaks, cracked polystyrene, plexiglass, and other transparent products produced by injection molding are mainly caused by the vertical direction of the tensile stress during the injection molding process. The use right polymer molecules exhibit heavy flow orientation and the difference in the breakage rate from the unoriented portion shows.
The solutions generally adopted for such problems are as follows:
- (1) Eliminate the interference of gas and other impurities, and fully dry the plastic.
- (2) Reduce the temperature of the material, adjust the temperature of the barrel in stages, and increase the temperature of the mold appropriately.
- (3) Increase the injection pressure and reduce the injection speed.
- (4) Increase or decrease the pre-plastic back pressure and reduce the screw speed.
- (5) Improve the exhaust condition of the flow channel and cavity.
- (6) Clean up possible clogging of the nozzle, runner and gate.
- (7) Shorten the molding cycle, and use the annealing method to eliminate the silver streaks after demoulding: keep the polystyrene at 78 ℃ for 15 minutes, or 50 ℃ for 1 hour, for polycarbonate, heat above 160 ℃ for several minutes .
Most quality problems in the production of plastic injection products are caused by process conditions, materials, or maintenance of machines and molds. Therefore, in order to produce high-quality, high-precision and high-level plastic products, it is necessary to control the entire production process, and to achieve the details of injection molds, injection molding equipment, the technical experience of operators, the production environment of the workshop and All aspects of raw materials have reached high standards.