In order to carry out the design of molds for plastic injection molding, it is necessary to determine the molding shrinkage ratio. In this course, rough guides of the molding shrinkage ratios are explained for the typical plastic materials used in injection molding.

[Table 1] is a list of the major thermoplastic materials, their molding shrinkage ratios, cavity surface temperatures, and injection molding pressures.

For more details, it is common practice to obtain the material catalogs and technical documents for each grade from the manufacturers of the molding materials and to use them as the reference materials for making decisions.

[Table 1] List of molding shrinkage ratios of major plastic materials