What are the causes of cracking defects in injection moulded parts processing

When we are processing injection moulded parts, we often have some unnecessary defects due to some minor reasons, which in turn cause some problems to our injection moulding process. Among these defects, the most common is cracking defects, so what are the reasons for cracking defects in injection moulded parts processing?
 

1, the proportion of recycled materials added to the raw materials, so that the raw materials shrinkage directional or uneven distribution of filler;
2, raw material plastic pollution, volatiles or poor drying;
3, improper design of mold release, mold release slope is small, the product wall is thin and has sharp corners and notches, resulting in stress concentration;
4、Short holding pressure and injection time, too long or too short cooling time;
5, low or uneven mould temperature, slow injection speed and low pressure;
6, improper moulding conditions, high stress and poor ejection;
7, improper use of release agents, uneven cooling of products after demoulding, etc.