https://www.tzhqmould.com/product/ Molten plastic must release heat before the molded part can be ejected without excessive deformation. If different areas of the part cool at different rates, internal stresses and uneven shrinkage may develop. The challenge becomes more noticeable with thick sections, deep ribs, complex cores, and parts with uneven wall thickness. Simply extending the cooling time may reduce some problems, but it can also make production less efficient.