Feman Tooling Co.,Limited
Feman Tooling Co.,Limited
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Causes of Coking in Injection Molding

There will inevitably have the injection product discolored coking appear black spots and so on during the injection mold processing. The general reason for this problem is that plastics, ultraviolet absorbent or antistatic agents are decomposed in the cylinder over heat. Or they remain in the barrel for too long and lead to decomposition, coking, and then with the injection molding cavity. The following will introduce why there is coking in injection molding mold.


Ⅰ. Machine

1. The heater control system gets out of control, resulting in overheating barrel and making injection molding mold decomposed and black.

2. Melt gets snapped in and hoarded because of the disadvantages of screw and barrel, suffering long time fixed heating and causing decomposition. The pad suite should be inspected to check whether there is wear or metal inside.

3. Some plastics such as ABS suffers high heat and gets crosslinking coking in the barrel. They are difficult to melt and are crushed by the screw and entrained into the workpiece if the particle shape is almost maintained.


Ⅱ. Mold

1. If the mold exhaust is not suitable, it is easy to Coke; Or the size of the pouring system is too small, shear too severe resulting in coking.

2. There is unproper oil lubricant and release agent.


Ⅲ. Injection plastic

If the plastic has too much volatile, too much humidity, too much impurity and too much reworked material, then it will be vulnerable to pollution.


Ⅳ. Processing

1. Extreme pressure, speed, backpressure and revolving speed may make plastic resolved.

2. The cartridge should be cleaned regularly to remove additives with worse tolerance than plastic.

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