The standard, which replaces the older DIN 16742 , is the primary international guideline for determining tolerances of plastic molded parts. Unlike metal components, plastic parts undergo significant shrinkage and environmental changes, making standard rigid-body tolerance chains (like ISO 286) often unsuitable. Core Tolerance System (Tolerance Groups)
When manufacturing plastic parts, achieving precise dimensions is significantly more challenging than working with metals. Shrinkage, material composition, and molding conditions all introduce variability. To standardize these variations, the International Organization for Standardization introduced ("Plastics molded parts — Tolerances and acceptance conditions"), which officially replaced the older DIN 16742 standard.
): Amorphous plastics (like Polycarbonate or ABS) experience low, uniform shrinkage (approx. 0.3% to 0.7%). Semi-crystalline plastics (like Polypropylene or Polyethylene) experience high, anisotropic shrinkage (approx. 1.5% to 3.0%), making them much harder to hold to tight TGs. iso 20457 tolerance table pdf
When designing or manufacturing plastic injection-molded parts, achieving perfect dimensional accuracy is a significant challenge. Unlike metals, plastics exhibit high shrinkage, thermal expansion, and viscoelastic behavior.
): The variations caused by fluctuations in injection pressure, melt temperature, cooling time, and ambient factory humidity. The total permissible tolerance ( AGcap A sub cap G ) is calculated geometrically combining these factors: The standard, which replaces the older DIN 16742
Standard commercial tolerances for typical industrial injection molding.
Since the standard is copyrighted, it must be legally purchased. You can obtain the official PDF from these authorized sources: material shrink behaviors
Always confirm that the table shows and includes the separate columns for parting line (typically labelled “F” for “flash line” in German-influenced documents).
Engineers utilize the as a primary tool to balance part functionality with production economics. Understanding the tolerance groups (TG), material shrink behaviors, and evaluation rules outlined in the standard is critical for successful part design.
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
These tolerances apply to dimensions that are influenced by factors outside of the mold cavity itself.