Overview
ISO 12180-2:2011 - Geometrical Product Specifications (GPS) - Cylindricity - Part 2: Specification operators defines the complete specification operator for cylindricity of complete integral cylindrical features. It specifies how cylindricity measurements are to be extracted, filtered and interpreted so that a cylindricity specification is unambiguous and repeatable. This Part is a GPS operator standard that complements ISO 12180‑1 (vocabulary and parameters) and follows the operator model of ISO 17450‑2.
Key topics and requirements
- Complete specification operator: An ordered, unambiguous set of specification operations (extraction, filtering, probe geometry, etc.) that together define the transmission band for the cylindricity surface.
- Probing system:
- Contacting stylus probing is part of the operator.
- Stylus tip geometry: theoretically spherical.
- Probing force: specified as 0 N (to exclude elastic deformation effects from the operator).
- Filtering and transmission band:
- Extraction always involves filtering; additional mean-line or non-linear filters (Gaussian, spline, wavelet, morphological) may be applied.
- The standard notes current practice uses a Gaussian filter, and highlights that the chosen filter affects cylindricity results.
- Ambiguities to avoid:
- ISO/TC 213 had not set defaults for undulation per revolution (UPR), probe tip radius, or method of association (reference cylinder) - these must be explicitly stated in a specification or the requirement is ambiguous.
- Sampling and aliasing:
- Annex A discusses harmonic content, sampling strategies and the Nyquist criterion to avoid aliasing; sampling intervals must be chosen relative to the highest harmonic present.
- Extraction strategies (Annex B):
- Bird-cage (high density both circumferentially and axially), roundness profiles, generatrix profiles, and point-sampling - each has different harmonic assessment capabilities.
- Compliance:
- Use ISO 14253‑1 for decision rules when proving conformance/non‑conformance.
Practical applications and users
Who uses ISO 12180‑2:2011:
- Metrology engineers, QA/QC teams and calibration laboratories that measure cylindricity on shafts, bores, pins and other cylindrical parts.
- Manufacturers in automotive, aerospace, bearings, hydraulics and precision machining where tight cylindrical form control is critical.
Practical use:
- To write unambiguous cylindricity specifications that include the extraction operator, filter, probe geometry and sampling strategy.
- To design measurement procedures (CMM, roundness/ cylindricity instruments) that avoid aliasing and ensure comparable results across suppliers and labs.
Related standards
Keywords: ISO 12180-2:2011, cylindricity, GPS, specification operators, stylus probe, Gaussian filter, Nyquist, extraction strategies, bird‑cage, UPR, ISO 17450-2.
Open preview (PDF)Geometrical product specifications (GPS) — Cylindricity — Part 2: Specification operators