Shrink Rate,Refers to how much the plastic material will shrink after cooled. This % of shrink is added to the part before the mold is designed. Every plastic material has its own shrink rate ranging from .001 per inch to as much as .060 per inch. Although most fall in between .004 and .021. It is important when selecting
a range of plastic materials that you may want to test before building the injection mold. For example if you wanted to
use ABS which is .006 per inch and Nylon which is .015 per inch you may want to build the injection mold to .010 or leave critical dimensions stock safe until a final material is selected.