The reason analysis that injection molding product cracks?
When the product is produced, there are cracks, including filamentous cracks on the surface of the product, micro-cracks, top whiteness and resulting in product loss. According to the cracking time, demoulding cracking and application cracking are mainly caused by the following aspects.
(1) Processing
1. Increased processing pressure, too fast speed, too much filling and injection, and too long holding time will cause excessive internal stress and cracking.
2. Adjust mold opening speed and pressure to prevent demoulding cracking caused by rapid strong pulling of products.
3. Adjust the mold temperature appropriately to make the product easy to demoulding, and lower the material temperature appropriately to prevent decomposition.
4. Prevent cracking caused by low mechanical strength caused by weld mark and plastic degradation.
5. Appropriate use of release agent, pay attention to often eliminate the membrane surface attached to the aerosol and other substances.
(2) Mold
1. The ejection should be balanced, the number of ejection rods and cross-sectional area should be enough, the inclined top of demoulding should be enough, and the cavity surface should be smooth enough, so as to prevent the cracking caused by the concentration of residual stress in ejection caused by external forces.
2. The product structure should not be too thin, and the transition department should adopt transition as far as possible to avoid sharp corners and chamfering resulting in stress concentration.
3. Use less metal inserts as far as possible to prevent the increase of internal stress caused by the different shrinkage rate of inserts and products.
4. The main channel is enough to remove the mold before the sprue material can be reached and solidified, so as to facilitate demoulding.
(3) Machine
Plasticizing capacity of injection molding machine should be appropriate, too small plasticizing is not sufficient to completely mix and become brittle, too large will degrade.
