Overview
EN ISO 18183-2:2024 - Geometrical product specifications (GPS) - Partition - Part 2: Nominal model specifies the methods used to partition a nominal model. It defines how a CAD model or drawing is subdivided into partitioned features (surfaces, edges, vertices and their sub-features) by applying the operations of selection, simplification and subdivision. The standard establishes a default nominal partition (the set of single surfaces) and describes rules needed to make specifications unambiguous and suitable for automated verification and modern manufacturing workflows.
Key topics and requirements
- Scope: Methods for partitioning nominal models used in product specification and verification.
- Partition operations: Clear definitions and examples for selection, simplification and subdivision to derive partitioned features from models or drawings.
- Default nominal partition: If not otherwise specified, the partition produced by single-surface decomposition is the default set of partitioned features.
- Model elements: Recognition that nominal models consist of surfaces, edges, blend edges and vertices; these form the initial partition.
- Duality for verification: Partition concepts are intended to be used symmetrically in specification and verification (see relation to ISO 18183-3).
- Relation to ISO GPS framework: This part applies concepts from ISO 18183-1 and sits within the ISO GPS matrix model; fundamental GPS rules (ISO 8015) and decision rules (ISO 14253-1) apply unless otherwise stated.
- Examples and informative annex: Illustrative figures and Annex A show relationships to the ISO GPS matrix model and how the document influences feature, measurement and conformity chains.
Applications and practical value
- Ensures consistent partitioning of nominal models for tolerance specification, metrology planning and inspection.
- Enables unambiguous interpretation of restricted-area tolerances, datum targets and combined features across CAD, drawings and inspection software.
- Supports automation: clear rules help CAD/CAM/inspection software and future autonomous manufacturing systems to identify and record partitioned features without manual intervention.
- Improves interoperability between design, quality and manufacturing teams by standardizing how model features are defined for verification.
Who should use this standard
- Design and CAD engineers defining nominal models and tolerances
- Metrology and quality engineers creating inspection plans
- CAM/inspection software developers implementing feature recognition and partitioning logic
- Standards committees and technical authors working on GPS-related specifications
- Manufacturers adopting automated verification and Industry 4.0 workflows
Related standards
- ISO 18183-1 (vocabulary and basic concepts) - concepts applied by this part
- ISO 18183-3 - verification aspects and duality principle
- ISO 8015 (fundamental GPS rules) and ISO 14253-1 (decision rules) - governing principles referenced in this document
- ISO GPS matrix model (ISO 14638) - contextual placement within the GPS system
Keywords: EN ISO 18183-2:2024, nominal model, partition, GPS, CAD partitioning, partitioned features, selection simplification subdivision, geometrical product specifications.