Establishing the correct tolerances with respect to the product function is of economic importance. The designer should be aware that dimensions with tight tolerances have a big influence on the costs of both product and mold.
Even slightly over specifying tolerances may adversely influence tool costs, injection molding conditions, and cycle time. It is recommended to indicate only critical dimensions with tolerances on a drawing.
Depending on the application, a division into three tolerance classes can be made:
- normal; price index 100
- accurate; technical injection molding; price index 170
- precise; precision injection molding; price index 300
The most important characteristics of the tolerance classes are shown in the figure below.
Characteristics of tolerance classes.