Cracking, including filament cracks on the surface of the part, microcracking, whitening, cracking, and damage due to the sticking of the part, the sticking of the flow path, or the traumatic failure, splitting and cracking according to the cracking time. There are mainly the following reasons.
(1) If the processing pressure is too large, the speed is too fast, the more filling, the injection and the holding time are too long, the internal stress will be too large and crack.
(2) Adjusting the mold opening speed and pressure to prevent demoulding cracking caused by rapid drawing of the workpiece.
(3) Appropriately increase the mold temperature, make the parts easy to demould, and appropriately reduce the material temperature to prevent decomposition.
(4) Prevention of cracking due to weld line degradation due to plastic degradation caused by plastic degradation.
(5) Appropriate use of the release agent, and attention should be paid to the elimination of substances such as aerosols adhering to the mold surface.
(6) Residual stress of the part can be reduced by eliminating the internal stress by annealing heat treatment immediately after molding to reduce the generation of cracks.
(1) The content of recycled materials is too high, resulting in too low strength of the parts.
(2) The humidity is too large, causing some plastics to react with water vapor, reducing the strength and causing cracking.
(3) The material itself is not suitable for the environment or quality that is being processed, and the pollution will cause cracking.