Causes of overheating discoloration of injection molded parts and improvement methods

There are many reasons for overheating discoloration of injection molded parts. For example, when the polymer is excessively heated, the molecular chain will split, and it will undergo thermal degradation or combustion. Sometimes only some yellow color changes can be seen, which also shows that slight thermal degradation has occurred. This thermal degradation is not only caused by the combustion of the polymer, but also by the sleeve agent in the polymer. Of course, when dealing with combustion defects, we must know where the defects appear. If the melt does not show color changes of coffee, yellow and black when cleaning, it means that the melt starts to burn after leaving the nozzle. We should check the main diameter, flow channel, water level and mold design, or correct the injection speed and pressure.

If the color is coffee stripe or color change during cleaning, it means that degradation occurs in the barrel and nozzle. But if you see coffee stripes and silver stripes at the same time, you need to doubt if there is something wrong with the moisture. If the position is fixed and the configuration of the finished parts is the same, then the combustion comes from the inspection valve or the end of the burner. If the color change is dispersed, the degradation occurs in the barrel and screw.

Improvement methods:


a. Plastic
. check and replace the mixing formula of plastic additives and reduce the proportion of turning abrasive

b. Mold
. optimize the tip angle of the molding, increase the diameter of the runner / gate, optimize the wall thickness of the molding, check the exhaust channel, check the heat flow channel system

c. Injection molding machine conditions
. reduce the injection capacity, reduce the injection melting temperature, reduce the screw rotation speed, reduce back pressure, optimize injection speed (s-f) in the stage, check whether the melt system operates normally, reduce the total cycle, check the cleaning of the drying system, check whether the injection system is normal and use the injection molding machine.