In the last lesson, while we explained a basic method of determining the cavity dimensions, in this lesson we describe an example of application of this method.

Application Example 1: When the dimensional tolerance is a single sided tolerance value (when it is not a ± tolerance value)

Let us consider the case when a dimension of the molded article is 22.

If the cavity is prepared based on this calculation result, since it can be considered that the probability of fluctuations in the dimensions of the molded article will be the same in the + direction as well as in the - direction, in case the shrinkage becomes larger than predicted, there is the danger that the - side tolerance will be exceeded.
In view of this, in the case of such single sided tolerance, the calculation of shrinkage is made aiming at the center of the width of tolerance.

Application Example 2: When the dimensional tolerance is a single sided tolerance value (when it is not a ± tolerance value)

Let us consider the case when a dimension of the molded item is 22.

Even when the cavity is prepared based on this result of calculation, as in the above example, in case the shrinkage becomes smaller than predicted, there is the danger that the + side tolerance will be exceeded.
In view of this, even in the case, the calculation of shrinkage is made aiming at the center of the width of tolerance.

In this manner, the cavity dimensions are determined appropriately for each dimensional tolerance of the molded article.