Overview
ISO 20457:2018 - Plastics moulded parts: Tolerances and acceptance conditions - defines practical manufacturing tolerances and acceptance rules for non‑porous plastic moulded parts. The standard covers general tolerances, surface profile tolerances within a specified datum system, and guidance for applying ISO‑GPS tools for dimensional and geometrical tolerancing. It applies primarily to injection moulding, injection‑compression, transfer, compression and rotational moulding of thermoplastics, thermoplastic elastomers and thermosets, and can be adopted for other plastic processes by agreement.
Key topics and requirements
- General tolerances and datum systems: Specifies default tolerances for integral features and surface profile tolerance referenced to a defined datum system.
- ISO‑GPS integration: Allows use of ISO geometrical product specification (GPS) tools for functional or special tolerancing needs.
- Dimensional and geometrical tolerancing: Guidance on tolerance grades for features of size, determination of tolerance grades, and application of geometrical tolerancing principles.
- Material and process factors: Addresses moulding compound properties such as moulding shrinkage, shrinkage anisotropies, and material stiffness/hardness that influence achievable tolerances.
- Feature‑specific rules: Covers tolerancing of draft angles, radii, freeform surfaces and angular dimensions.
- Acceptance conditions (ABF): Defines acceptance criteria and production validation practices for moulded part production, including capability validation and production expense considerations.
- Scope limits: Does not address surface imperfections like sink marks, flow marks, roughness or joint lines and does not replace specific product standard requirements.
Practical applications and users
ISO 20457:2018 is intended for professionals involved in the design, manufacture and quality assurance of plastic moulded parts:
- Part designers: to specify functionally required tolerances that account for polymer behaviour and moulding shrinkage.
- Toolmakers and tool designers: to agree shrinkage compensation and tool contour tolerances.
- Manufacturers and process engineers: to set realistic production tolerances, validate machine/process capability, and reduce scrap.
- Quality engineers and inspectors: to apply dimensional and geometrical tolerancing and acceptance criteria in production control and inspection plans.
- Procurement and contract managers: to define contractual tolerances and acceptance conditions between parties.
Related standards
Relevant ISO documents referenced in ISO 20457:2018 include:
ISO 20457:2018 helps bridge material/process realities and geometric tolerancing, making it a practical standard for optimizing plastic part design, tooling and quality control.