Unlike metal machining tolerances, plastic parts require special consideration due to material shrinkage, warpage, moisture absorption, and processing conditions. ISO 20457 addresses these variables by providing tolerance classes that account for the complexity of the plastic material and the moulding process.
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.
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.
Would you also like a comparison table between ISO 20457 and the older DIN 16901, or a sample drawing note for applying these tolerances? iso 20457 tolerance table pdf
ISO 20457 splits deviations into two distinct categories, which are combined to create the final total tolerance: Mold Making Tolerances ( AWcap A sub cap W
While ISO 9908 outlines the general design and performance requirements, ISO 20457 gets into the granular details of the physical dimensions. It defines the permissible deviations from the nominal dimensions for various pump parts, such as impellers, shafts, housings, and seals.
The standard also provides guidance for angular dimensions and radii. Representative values for general tolerances under ISO 2768m include: For a 45mm long housing, you look at the "30 up to 120" row
(e.g., glass fibers) reduce shrinkage but introduce anisotropy (different shrinkage rates parallel and perpendicular to the flow). 4. Post-Molding Environmental Factors
Standard industrial tolerances. This is the sweet spot for most commercial plastic injection molded components.
Note: This table is for illustrative purposes. Always cross-reference official ISO documents for production-level calculations. Tooling vs. Molding Tolerances Would you also like a comparison table between
is the current international standard for determining manufacturing tolerances of plastic molded parts . It replaces older standards like ISO 8062 and is closely aligned with the German DIN 16742. This standard is vital for designers and manufacturers to agree on achievable precision without driving up costs through unnecessary accuracy requirements. Key Tolerance Groups (TG)
Several industry sources confirm these general assignments. ISO 20457 TG4 is typically applied for precision injection molded parts such as gears, TG5 for housing parts, and TG6 for packaging components. In the automotive industry, critical components typically require TG4 or higher, with deviations measured in micrometers.
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The (which replaced the older DIN 16742 and DIN 16901 standards) is the definitive international framework for establishing dimensional, shape, and position tolerances for plastic molded parts. While a complete, enforceable "ISO 20457 tolerance table PDF" must be officially purchased through standard bodies like the ISO Store or the ANSI Webstore due to digital rights management (DRM) and copyright protections, understanding its structural tolerance groups (TG1 to TG9) is crucial for accurate part design and process engineering.
In practice, ISO 20457 defines based on: