Why is the injection molded product to be annealed?

For example, in the thin and thick intersection of the product, the thick part is slow to cool down, and the thin part is cooled faster, and the joint is unevenly contracted, resulting in stress concentration. This phenomenon is more pronounced around the metal inserts. When there is no mold, there is no abnormality on the surface. It may be a few days, maybe a few days, maybe half a year or longer. Under the action of external factors (temperature, pressure, polar solution, etc.), cracks may occur in the stress concentration part, and even cracking may occur. Or deformation.

In order to eliminate or reduce internal stress in the molded article and to avoid large deformation or cracking of the product during storage or application, some of the formed products are annealed.

Annealed products are generally PC, PS and other plastics. For POM, PVC and other plastics, the annealing process must be performed immediately after demolding.

The annealing treatment method is: placing the injection molded part in a heating medium (oil, liquid paraffin, glycerin) having a constant temperature or an oven having a hot air circulation, and the heating temperature is lower than about 20 ° C of the heat distortion temperature of the workpiece.

After the heat treatment time has reached the requirements, the parts are slowly cooled to room temperature with the medium. Note that if the treated product is cooled rapidly or taken out directly from the heat treatment medium, the product will generate new internal stress due to the difference in cooling rate.