Overview
ISO 20457:2026 - Plastics Moulded Parts - Tolerances and Acceptance Conditions is an essential ISO standard for defining the geometrical and dimensional tolerances, as well as acceptance conditions, applicable to plastic moulded parts. The standard accommodates the specific characteristics of plastics, addressing their unique manufacturing processes and material behaviors. It ensures effective communication between part designers, manufacturers, and other stakeholders by providing a consistent framework for tolerances and acceptance within the plastics industry.
ISO 20457:2026 applies to non-porous moulded parts made from thermoplastics, thermoplastic elastomers, and thermosets, produced via injection moulding and related processes. It is also applicable to other plastics processing methods if agreed upon contractually. The standard does not cover surface imperfections such as sink marks, undesired flow structures, or roughness.
Key Topics
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Geometrical and Dimensional Tolerances
Establishes guidelines for direct tolerances on functional features and general tolerances for non-functional features in plastic moulded parts.
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Acceptance Conditions
Specifies acceptance criteria for plastic moulded parts, including manufacturing limits and verification obligations for sample inspection and production.
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Modification of Drawing Defaults
Adjusts standard drawing parameters (in accordance with ISO 8015) for the specific environmental and manufacturing conditions in the plastics sector.
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Tolerancing Procedures
Details when and how direct (individual) tolerances should be applied, and clarifies the use of general tolerances as defined by the part function and manufacturing capabilities.
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Environmental and Material Factors
Considers factors such as moulding shrinkage, anisotropy, material stiffness, and processing conditions that affect tolerance accuracy and repeatability.
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Datum Systems in Plastics
Provides guidance on appropriate referencing systems for plastic parts to ensure accuracy and repeatability in measurement, taking into account the flexibility and deformation potential of plastic materials.
Applications
ISO 20457:2026 delivers practical value for a range of users involved in the design, manufacturing, and quality assurance of plastic moulded parts:
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Product Designers
Gain clear guidelines for specifying achievable and cost-effective tolerances, improving cooperation with manufacturers and avoiding unrealistic requirements.
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Manufacturers
Use the standard as a basis for evaluating manufacturability, production feasibility, and the validation of conformance to dimensional requirements during initial and ongoing production.
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Quality Assurance and Inspection Teams
Benefit from clear criteria for acceptance and rejection of plastic moulded parts, leading to consistent product quality and minimized disputes.
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Suppliers and Procurement Professionals
Reference a common standard when specifying requirements in contracts and ensuring suppliers adhere to industry-accepted tolerances and acceptance conditions.
Relevant industries include automotive, consumer goods, medical devices, electronics, and any sector where precision plastic parts are produced via processes like injection moulding, compression moulding, and rotational moulding.
Related Standards
For comprehensive compliance and best practices, ISO 20457:2026 should be used alongside these related standards:
- ISO 8015 - Geometrical product specifications (GPS) - Fundamentals, concepts, principles, and rules
- ISO 294-4 - Plastics - Injection moulding of test specimens of thermoplastic materials - Determination of moulding shrinkage
- ISO 2577 - Plastics - Thermosetting moulding materials - Determination of shrinkage
- ISO 5459 - Geometrical tolerancing - Datums and datum systems
- ISO 10579 - Non-rigid parts - Definitions and tolerancing
- ISO 14405-1 - Dimensional tolerancing - Linear sizes (GPS)
By referencing ISO 20457:2026 and these related standards, organizations ensure robust, industry-approved practices in the specification, production, and quality assurance of plastic moulded parts, supporting both functional performance and economic manufacturing.
