Discoloration refers to the inconsistency between the surface color of the formed parts and the required color. Discoloration may be caused by a variety of reasons, including injection molding machine, plastic mold, injection process and raw materials.
(1) Injection molding machine
① The equipment is not clean and needs cleaning. Dust or powder deposited in the barrel contaminates and discolors the material;
② Temperature control failure caused by temperature controller or heating system failure;
③ There are obstacles in the barrel, which lead to the decomposition of the plastic; foreign metal objects are stuck in the barrel or spiral channel, which are grinded continuously, resulting in the discoloration of the plastic;
(2) Plastic mold
① The poor exhaust of the plastic mold results in the compression of the plastic in the heat insulation environment, so the material is easy to burn when it reacts with oxygen under high temperature and pressure;
② Too much lubricant / release agent in the barrel. When cleaning the barrel, remove additives with worse heat resistance than plastics, such as antistatic agents;
③ The size of nozzle, gate and sprue is too small;
(3) Injection molding process
① Screw speed / back pressure of preform is too high;
② Too high barrel / nozzle temperature;
③ Injection pressure is too high / injection time is too long / injection speed is too fast, resulting in product discoloration.
(4) Raw materials
① There are impurities in the material;
② Excessive moisture content in the material;
③ Colorant / additive decomposition.
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PTJmould is a China mold maker of plastic molds- injection mold, die casting moulds, plastic blow molding, rotational molding, medical plastic injection molding, two shot plastic injection molding, insert molding, overmolding, metal injection molding, micro injection molding, powder injection molding, ceramic injection molding, liquid injection molding, husky injection molding, household mold, casting mold, die mold tool, custom molds, china moulds, rapid prototyping tooling, plastic prototyping tooling, punch press tooling, die and tooling for mobile/ cell phone parts, automotive parts, vacuum cleaners, rechargeable tools, telephones, copiers, computers, multimedia speakers, and many other electronic products and household appliances. And also a plastic product manufacturer, mold manufacturer China– plastic parts, plastic water tank, plastic balls, plastic containers, plastic buckle, plastic anchor, plastic hanger, plastic spoon, plastic pipe fitting, plastic tumble, plastic tableware, plastic cups, plastic bottles, plastic tray, plastic cosmetic container, plastic case, plastic food container, plastic chairs, plastic caps, plastic cap closure, plastic tubes, plastic water pipes, plastic knobs, plastic tubing, plastic utility boxes, plastic racks and so on.
Link to this article：Discoloration of common problems in plastic injection molding
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