Used for large components, highly flexible elastomers, or recycled materials where structural integrity takes precedence over strict dimensional accuracy. Material Properties and Tolerance Determination
If tolerances are too loose, parts may not fit or perform as designed.
Note: The format +X / 0 indicates that the pipe can be larger than nominal by X mm, but cannot be smaller than the nominal size (ensuring it can seal).
Preventing overly tight tolerances that increase tooling costs unnecessarily. iso 20457 tolerance table pdf
Understanding dimensional tolerances for plastic injection molded parts is crucial for designers, engineers, and manufacturers. Unlike metals, plastics are sensitive to thermal expansion, moisture absorption, and molding process variations. (which supersedes DIN 16742) provides the standardized framework for these tolerances, replacing older, less applicable metal-based standards.
Used for Critical-to-Quality (CTQ) dimensions, such as snap-fits or bearing housings, though it requires more expensive tooling and process control.
(and its German equivalent DIN 16742) is the international standard for dimensional and geometrical tolerances of plastic molded parts . It replaces older standards like DIN 16901 to provide a more consistent framework for injection molding and related processes. Key Tolerance Tables & TG Groups Used for large components, highly flexible elastomers, or
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It reduces disputes between part designers and molders by setting clear boundaries. Factors Influencing Plastic Tolerances
Utilizing a proper is essential because: While a complete
The distinction between W-type (tool-related) and NW-type (non-tool-related) dimensions is critical. Dimensions affected by moving mold components (slides, parting lines, core pulls) inherently have wider tolerances than cavity-controlled dimensions.
TG6 is a common baseline for thermoplastic injection molding. Below is a summary of the general tolerances for this group: Nominal Range (mm) Tool-Specific (W) (± mm) Non-Tool-Specific (NW) (± mm) 3 to 6 6 to 10 10 to 18 18 to 30 30 to 50 50 to 80 80 to 120 Source: Derived from OKW-Tolerances-en (PDF) . Tolerance Determination Process
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
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.