Analysis of possible factors of black spot discoloration of injection molded products

1. On the machine

Due to uncontrolled heating control system, the barrel is overheated, resulting in decomposition and blackening.
Due to the defect of screw or barrel, the molten material is stuck in and hoarded, which is subjected to long time fixed heating causing decomposition.
Some plastics, such as ABS, are cross-linked and coked by high heat in the barrel, and are difficult to melt while maintaining almost the original particle shape, and are crushed by the screw and entrained into the parts.

2. Mould

The mold exhaust is not smooth, easy to scorch, or the size of the casting system is too small, shearing too much to cause coking.
There are inappropriate oil lubricants and mold release agents in the mold.

3. Plastic

Too much plastic volatiles, too much humidity, too many impurities, too much recycled material, contaminated.

4. Processing

Too much pressure, too high speed, too much back pressure, too fast speed can make the material temperature decomposition.
The barrel should be cleaned regularly to remove additives that are worse than the plastic resistance.