Because ISO 20457 relies heavily on material shrinkage, always state the exact manufacturer data sheet grade (e.g., Sabic Cycolac ABS MG47 ) on the drawing.
ISO 20457 has become the global benchmark for tolerancing injection-molded plastic parts. By adopting this standard, designers and engineers can move away from guesswork and ambiguous specifications.
Find the size row of your feature (e.g., 1–3mm, 10–18mm, 50–80mm).
Plastics behave differently based on their molecular structure. iso 20457 tolerance table pdf
To develop a piece or select the correct table value, you must consider:
Find the row in the table corresponding to your part's length, width, or diameter. For a 45mm long housing, you look at the "30 up to 120" row.
ISO 20457:2018 is the primary international standard for determining for non-porous plastic molded parts. It replaces the older DIN 16742 standard and provides a systematic way to calculate achievable tolerances based on material properties and manufacturing processes. Unlike metal machining standards, ISO 20457 accounts for the unique behavior of plastics, such as mold shrinkage and environmental sensitivity. Key Components of ISO 20457 Because ISO 20457 relies heavily on material shrinkage,
The ISO 20457 standard establishes a standardized methodology to determine geometrically and dimensionally achievable tolerances for plastic molded parts. It covers a wide range of non-porous molding processes, including: Injection molding Injection compression molding Transfer molding Compression molding Rotational molding Why Metals and Plastics Cannot Use the Same Tolerances
While the full PDF document contains extensive calculation formulas for custom variations, standard applications rely on generalized reference tables. Below is a simplified representation of typical standard tolerance values (TG5 and TG6) for nominal dimensions. Nominal Dimension Range (mm) TG5 / Standard Precision ( ±plus or minus TG6 / Commercial Grade ( ±plus or minus 1 to 3 3 to 6 6 to 10 10 to 18 18 to 30 30 to 50 50 to 80 80 to 120 120 to 180 180 to 250
The most sought-after component of this standard is the . Typically, the PDF version of ISO 20457 contains several critical tables, but one stands out: the table linking nominal sizes to permissible deviations for linear dimensions and angles. Find the size row of your feature (e
). For the definitive, legally binding matrix, always consult the official ISO 20457 PDF documentation. Nominal Dimension (mm) 3 to 6 6 to 10 10 to 18 18 to 30 30 to 50 50 to 80 80 to 120 120 to 180 180 to 250 Factors Influencing Plastic Molded Tolerances
Because ISO 20457 is a classification standard, its tables do not provide the raw numbers for every single dimension (that is the job of ISO 286, ISO 2768, etc.). Instead, it provides a .