In the manufacturing of plastic parts, applying standard metal tolerances (like ISO 2768) is not practical. Plastics behave differently during and after cooling.

Unlike metals, plastic dimensions are highly dynamic. ISO 20457 determines tolerance groups based on four major variables:

ISO 20457:2018 was developed to serve as the true international successor to DIN 16901. It broadened the scope of tolerancing while introducing a more refined and objective system. The new standard introduced , a significant increase from the six tolerance groups (110–160) used in the old DIN 16901 system. This expansion provides designers with greater flexibility and control when specifying precision levels for their parts.

Overall part performance, fits, clearances, and functional interactions between separate molded pieces. 2. Series W (Tool-Dependent Tolerances)

Stop fighting shrinkage. Embrace ISO 20457.

ISO 20457 categorizes tolerances into two distinct application groups based on whether the dimensions are tool-dependent or affected by post-molding assembly processes: 1. Series NW (Non-Tool-Dependent / Assembly Tolerances)

ISO 20457 is not a one-size-fits-all document. It is a sophisticated system built to handle the complexities of plastic part manufacturing. Its most important features include:

It covers geometric dimensioning and tolerancing (GD&T) specific to plastics, including straightness, flatness, and roundness.

Ensure your dimensional checks are specified at a defined measurement plane, as draft angles inherently alter the cross-sectional dimensions of a part along its depth.

Tight, high-precision tolerances. Hard to achieve; requires optimized tooling, stable materials, and advanced process control.

Always confirm that the table shows and includes the separate columns for parting line (typically labelled “F” for “flash line” in German-influenced documents).

Here’s a clear, professional write-up on and its tolerance tables, suitable for inclusion in a technical document, training material, or engineering summary.

The standard categorizes dimensions into groups (TG1 to TG9), where is the most common industry standard for thermoplastics. Dimensional Deviations: