(1) Definition of defects

Discoloration, yellowing refers to the difference from the specified color of the product, the main local presentation of yellowing, blackening, and so on.

(2) Cause classification

①Materials

a. The use of unsuitable color materials, heat resistance is not enough, resulting in the material in the cylinder has been sold or yellowing.

b. Dehumidification drying temperature is too high, or too long, so that the material itself discoloration.

② mold reasons

The gate is too small, and the injection process generates shear heat, causing the material to decompose.

③ Injection molding process reasons

a. The material is too high.

b. Retention time in the barrel is too long. c. Injection speed is too fast, and too much shear heat is generated during the flow process. d. There is an abnormal stoppage in the production process.

④ Hot runner causes

A. There is dead space in the hot runner channel.

B. The hot runner processing causes the material to stay for a long time.

(3) Solutions

①Material Countermeasures

A. Check the temperature resistance and thermal stability of the colorants or additives used.

B. Check the drying degree and time.

C. Check the temperature resistance and thermal stability of the colorants or additives used.

②Mold Countermeasures

Increase the gate or change it to another type of gate.

③Injection molding process countermeasures

A. Check the melt temperature and reduce the material temperature; reduce the screw speed and back pressure during plasticizing.

B. Check the injection volume and make sure that the correct plasticizing unit is used.

C. Reduce the injection speed to reduce the shear heating phenomenon.

D. Make sure that there is no prolonged shutdown during the production process, and when shutdown, the temperature of the barrel needs to be reduced.

E. Check the temperature of the barrel.

F. Check the temperature of the barrel.

G. Check the temperature of the barrel.

H. Check the temperature of the barrel.

I. Check the temperature of the barrel and make sure that it is not too hot.

④ Hot runner countermeasures

A. Improve the hot runner channel to eliminate the dead space.

B. Polishing the hot runner channel.

C. Polishing the hot runner channel.

D. Make sure that the hot runner channel is not too hot.

---- The above content is selected from “Injection Molding Use of Technology”, thank you for your attention to Fomtec Machine!