Reasons for cracking of plastic products

（1） Cracking caused by residual stress
The residual stress of plastic injection mold manufacturers is mainly caused by the following three conditions, namely, overfilling, demoulding and metal inserts. As the crack caused by overfilling, the solution can be mainly in the following aspects:
(1) Because the pressure loss of the straight gate is small, if the crack mainly occurs near the straight gate, the multi-point distribution gate, side gate and handle gate can be considered.
(2) On the premise of ensuring that the resin does not decompose and deteriorate, properly increasing the resin temperature can reduce the melt viscosity, improve the fluidity, and also reduce the injection pressure to reduce the stress.
(3) The plastic injection mold processing manufacturer pointed out that in general, the stress is easy to occur when the mold temperature is low, and the temperature should be appropriately increased. However, when the injection speed is higher, even if the mold temperature is lower, the stress generation can be reduced.
(4) If the injection and pressure holding time is too long, it will also produce stress, so shorten it appropriately or carry out several pressure holding switching effects
(5) Non-crystallic resins, such as AS resin, ABS resin, PMMA resin, etc., are more likely to produce residual stress than crystalline resins, such as polyethylene and polyformaldehyde, which should be noted.
When the plastic injection mold processing factory releases the mold, due to the small release angle, the mold glue and the rough punch, the ejection force is too large, resulting in stress, and sometimes even whitening or cracking around the ejection rod. The cause can be determined by carefully observing the location of cracking.
When plastic injection mold manufacturers insert metal parts during injection molding, it is easy to produce stress and crack after a period of time, which is extremely harmful. This is mainly due to the great difference in the thermal expansion coefficient of metal and resin, which causes stress, and over time, the stress exceeds the strength of the gradually deteriorated resin material and causes cracks.
（2） Cracking caused by external stress
The external stress here is mainly caused by stress concentration due to unreasonable design, especially at sharp corners.
（3） Cracking caused by external environment
Water degradation caused by chemicals, moisture absorption, and excessive use of recycled materials will degrade the physical properties and cause cracking.