It was already explained that it is very important to determine the molding shrinkage ratio for designing the molds for plastic injection molding. Here we would like to explain some guides to the molding shrinkage ratio of some typical plastic resins.

Table 1 shows some major thermoplastic plastic resins and their molding shrinkage ratios, cavity surface temperatures, and injection molding pressures. For more details, it is common to obtain the material catalogs or technical documents for each grade of material from the manufacturer of the plastic resin and use those documents for making this decision.

* Unless otherwise stated, the values given here are for natural resins.