Once molten plastic has been injected into the mold cavity, it takes time before the molding has cooled and become sufficiently rigid to allow it to be demolded. This period is called the cooling time and often forms a significant part of the molding cycle.

There are two important reasons why we need the cooling time:

1. To help us design the mold’s cooling system
We need to know how efficient the cooling system should be in order to remove a certain quantity of heat energy from the molten polymer in a given time.

2. To determine the cost of each molding
The cooling time is part of the overall cycle time, on which the molding-cost calculation is based.

In this free article, a simple method of calculating cooling times will be described. Since the calculation produces only a rough estimate, it is important to understand what assumptions and simplifications are made in order to be able to interpret the results properly.