Discussion on the possible factors of black spot discoloration in injection mold

Injection molding machine mold, I believe we all know, the main production of plastic products as a tool; In the manufacturing process of general injection mold, we often encounter some common problems, such as black spots, or discoloration and coking of injection products. However, the main reason for these problems is that the injection products stay in the barrel for a long time, which leads to the decomposition and coking of injection products and the formation of injection cavity with molten materials. What are the possible factors of black spot discoloration of injection molding machine in injection mold?

1. Machine side:

(1) Because the heating control system on the machine is not working, it causes the inner of the material cylinder to overheat, which causes the decomposition to turn black.

(2) Because of the defects of screw and barrel, the molten material is stuck and accumulated. Plastic is decomposed after a long time fixing and heating on the machine. At this time, the staff need to check whether the rubber head kit is worn and whether there is any metal foreign matter inside.

(3) Some plastics can be cross-linked and coking when the original particle shape is almost maintained, especially in the material barrel due to high heat. These plastics are difficult to melt, so that they are finally crushed by screw and then brought into the production.

2. Mold aspect:

(1) Generally, if the exhaust gas of the mold is not smooth, it is easy to burn. It is also that the size of the pouring system of the mold is too small, or the coking caused by too much shearing.

(2) The mold with suitable oil lubricants, release agents, etc., will also appear black spots.

3. plastic:

Too much volatile matter, too much humidity, too much impurity, too much recycled material, contaminated.

4. Processing:

(1) Too much pressure, too high speed, too much back pressure, too fast speed will cause material temperature decomposition.

(2) The barrel shall be cleaned regularly to remove additives that are less resistant than plastic.