What to do if there is a black spot problem in the injection molding machine mold

- 2021-07-13-

Generally, during the manufacturing process of injection molds, we often encounter some common problems, such as often finding black spots, or causing discoloration and coking of injection products, but the main reason for these problems is that the injection products stay in the barrel. The time is too long, which leads to the decomposition and coking of the injection molded product, which is formed when the molten material is injected into the cavity.

What are the possible factors for black spots and discoloration in the injection mold of the injection molding machine?

1. For the machine:
(1) Because the heating control system on the machine fails to operate, the inside of the barrel is overheated to cause decomposition and blackening.
(2) Because of the defects of the screw and barrel, the melt is jammed and accumulated, and the plastic is decomposed after being fixed and heated for a long time on the machine. At this time, the staff needs to check whether the rubber head kit is worn or not and whether there are metal foreign objects in it.
(3) There are some plastics that almost maintain the original particle shape, especially in the barrel due to cross-linking and coking. These plastics are difficult to melt, so that they are crushed by the screw and entrained into the part.

2, mold aspect:
(1) Generally, the mold on the mold is easy to scorch if the exhaust is not smooth, and the size of the mold's gating system is too small, or the coking is caused by too much shear.
(2) If suitable oil lubricants and mold release agents are used in the mold, black spots may also appear.
3. Plastic aspect:
Too much plastic volatiles, too much humidity, too much impurities, too much recycled materials, and contaminated.

4. Processing aspects:
(1) Too much pressure, too high speed, too much back pressure, and too fast speed will decompose the material temperature.
(2) The barrel should be cleaned regularly to remove additives that are less resistant than plastic.