Unlike metal fabrication, plastic injection molding relies on raw material behavior, part geometry, tool construction, and process variables. ISO 20457 categorizes these dynamics into nine designated , representing a spectrum from extreme high-precision to general-purpose molding.
The standard distinguishes between two fundamental types of dimensions based on their relationship to the mold:
For shorter legs (< 10mm), the deviation is often given as a fixed value (e.g., ± 30 minutes for coarse, ± 10 minutes for fine). iso 20457 tolerance table pdf
To develop a piece or select the correct table value, you must consider:
Post-molding shrinkage, storage conditions, environmental aging, and the assembly of multiple components. To develop a piece or select the correct
): Dimensions affected by moving parts of the mold, such as the parting line, sliders, lifters, or cores. They require larger tolerances due to tool shifting or clamping variations. ISO 20457 Tolerance Grades (TG1 to TG9)
To get the :
If you need to calculate a specific for a project, feel free to share your nominal dimensions , plastic material type , and whether the features are tool-dependent , and I can help you find the exact values. Share public link
and precision classes to define allowable deviations. A critical requirement is that a callout must include the grade and environmental conditioning (e.g., ISO 20457–TG6 + 23°C/50%RH ) to be enforceable. Super-Ingenuity Tolerance Categories (Materials) ISO 20457 Tolerance Grades (TG1 to TG9) To