One, what is cracked white?
Cracked white: crack is a more common plastic defects, including the surface of the workpiece filamentous crack, micro-crack, top white, cracking and sticky mold due to parts, flow path sticky mold caused by trauma, according to cracking time Divided into stripping cracking and application cracking.
The main reason is due to stress deformation (mainly residual stress, external stress and stress generated by the external environment deformation.) As shown
Second, how to improve?
1. Material:
The appropriate use of release agent, pay attention to often eliminate the mold surface attached to the gas mist and other substances;
Before the molding process of the material for the full drying;
Note that coatings and diluents that do not crack are selected.
2. Molding process:
To avoid the plasticization stage of poor feeding and involved in the air;
Improve the melt temperature and mold temperature, to ensure that the melt flow on the basis of the injection pressure should be reduced;
Reduce the screw speed, injection speed, slow down the melt through the initial gate speed, the use of multi-stage injection molding;
Adjust the mold speed and pressure, to avoid the rapid tensile products caused by stripping cracking;
To avoid due to welding marks, plastic degradation caused by the strength of the earth and cracking;
The generation of cracks is reduced by eliminating the internal stress by performing an annealing treatment immediately after molding.
If the surface of the plastic parts has been cracked, you can consider the way to take the annealing to eliminate the annealing process to lower than the plastic parts of the heat distortion temperature of about 5 ℃, fully heated plastic parts about 1 hour, and then slowly cooling, It is best to produce a cracked plastic parts after the annealing process immediately, which is conducive to the elimination of cracks, but cracks in the cracks left in the residual stress, paint the solvent is easy to crack into the crack at the crack.