Geometrical product specifications (GPS) - Population specification (ISO 18391:2016)

ISO 18391:2016 defines rules to establish and to indicate population specifications, which are used to specify conditions on population characteristics, which are established from a set of characteristic values obtained one on each workpiece of a population of workpieces.
A population specification (as applied to a population of workpieces considered as a collection and not as individual items) can be seen as a complementary requirement to the individual specification (as applied to each workpiece considered as individual items). Population specifications express the statistical hypotheses used on the population of workpieces.
NOTE 1 A population specification is a complement to an individual GPS specification.
NOTE 2 ISO 18391:2016 is not intended to mandate a given tolerancing method or how to calculate tolerance values. Its intent is to specify tools to allow the expression of population specifications.

Geometrische Produktspezifikation (GPS) - Populationsspezifikation (ISO 18391:2016)

Diese Internationale Norm definiert Regeln , um Populationsspezifikationen einzuführen und anzugeben, die verwendet werden, um Bedingungen für Populationsmerkmale festzulegen, welche aus einer Menge von Merkmalswerten bestimmt werden, die von jedem Werkstück in einer Population von Werkstücken erhalten werden.
Eine Populationsspezifikation (wie sie auf eine Population von Werkstücken zutrifft, die als Sammlung und nicht als Einzelstücke betrachtet werden) kann als eine zusätzliche Anforderung an die einzelne Spezifikation betrachtet werden (wie sie auf jedes Werkstück, das als Einzelstück betrachtet wird, zutrifft). Populationsspezifikationen drücken die statistische Hypothese aus, die für die Population von Werkstücken verwendet wird.
ANMERKUNG 1   Eine Populationsspezifikation ist ein Komplement einer einzelnen GPS-Spezifikation.
ANMERKUNG 2   Diese Internationale Norm ist nicht dazu vorgesehen, ein bestimmtes Verfahren zur Tolerierung festzulegen oder ein Verfahren zur Berechnung von Toleranzwerten zu bestimmen. Ihre Absicht ist es, Werkzeuge festzulegen, welche die Formulierung von Populationsspezifikationen zulässt.

Spécification géométrique des produits (GPS) - Spécification de population (ISO 18391:2016)

ISO 18391:2016 définit des règles pour établir et indiquer des spécifications de population, lesquelles sont utilisées pour spécifier des conditions se rapportant à des caractéristiques de population, établies à partir d'un ensemble de valeurs caractéristiques obtenues sur chaque pièce d'une population de pièces.
Une spécification de population (applicable à une population de pièces considérée en tant que collection et non en tant qu'éléments individuels) peut être vue comme une exigence complémentaire à la spécification individuelle (applicable à chaque pièce considérée en tant qu'éléments individuels). Des spécifications de population expriment les hypothèses statistiques utilisées sur la population de pièces.
NOTE 1 Une spécification de population est un complément à une spécification GPS individuelle.
NOTE 2 ISO 18391:2016 n'a pas pour objectif d'imposer une méthode de tolérancement donnée ou une méthode de calcul des valeurs de tolérance. Son objectif est de spécifier les outils permettant d'exprimer des spécifications de population.

Specifikacija geometrijskih veličin izdelka (GPS) - Populacijska specifikacija (ISO 18391:2016)

Ta mednarodni standard vsebuje osnovne informacije glede populacijskih specifikacij. Cilj teh je določiti populacijo obdelovancev, zahteve v povezavi z lastnostnmi, ki so merljive z upoštevanjem populacije pridobljenih vrednosti posameznega obdelovanca v populaciji obdelovancev.

General Information

Status
Published
Publication Date
01-Nov-2016
Current Stage
6060 - Definitive text made available (DAV) - Publishing
Due Date
02-Nov-2016
Completion Date
02-Nov-2016

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SLOVENSKI STANDARD
SIST EN ISO 18391:2017
01-januar-2017

6SHFLILNDFLMDJHRPHWULMVNLKYHOLþLQL]GHOND *36 3RSXODFLMVNDVSHFLILNDFLMD ,62



Geometrical product specification (GPS) - Population specification (ISO 18391:2016)

Geometrische Produktspezifikation (GPS) - Populationsspezifikation (ISO 18391:2016)

Spécification géométrique des produits - Spécification de population (ISO 18391:2016)

Ta slovenski standard je istoveten z: EN ISO 18391:2016
ICS:
17.040.40 6SHFLILNDFLMDJHRPHWULMVNLK Geometrical Product
YHOLþLQL]GHOND *36 Specification (GPS)
SIST EN ISO 18391:2017 en,fr,de

2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

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SIST EN ISO 18391:2017
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SIST EN ISO 18391:2017
EN ISO 18391
EUROPEAN STANDARD
NORME EUROPÉENNE
November 2016
EUROPÄISCHE NORM
ICS 17.040.40
English Version
Geometrical product specifications (GPS) - Population
specification (ISO 18391:2016)

Spécification géométrique des produits (GPS) - Geometrische Produktspezifikation (GPS) -

Spécification de population (ISO 18391:2016) Populationsspezifikation (ISO 18391:2016)

This European Standard was approved by CEN on 28 August 2016.

CEN members are bound to comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this

European Standard the status of a national standard without any alteration. Up-to-date lists and bibliographical references

concerning such national standards may be obtained on application to the CEN-CENELEC Management Centre or to any CEN

member.

This European Standard exists in three official versions (English, French, German). A version in any other language made by

translation under the responsibility of a CEN member into its own language and notified to the CEN-CENELEC Management

Centre has the same status as the official versions.

CEN members are the national standards bodies of Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech Republic, Denmark, Estonia,

Finland, Former Yugoslav Republic of Macedonia, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania,

Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland, Turkey and

United Kingdom.
EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION
EUROPÄISCHES KOMITEE FÜR NORMUNG
CEN-CENELEC Management Centre: Avenue Marnix 17, B-1000 Brussels

© 2016 CEN All rights of exploitation in any form and by any means reserved Ref. No. EN ISO 18391:2016 E

worldwide for CEN national Members.
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SIST EN ISO 18391:2017
EN ISO 18391:2016 (E)
Contents Page

European foreword ....................................................................................................................................................... 3

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SIST EN ISO 18391:2017
EN ISO 18391:2016 (E)
European foreword

This document (EN ISO 18391:2016) has been prepared by Technical Committee ISO/TC 213

“Dimensional and geometrical product specifications and verification” in collaboration with Technical

Committee CEN/TC 290 “Dimensional and geometrical product specification and verification” the

secretariat of which is held by AFNOR.

This European Standard shall be given the status of a national standard, either by publication of an

identical text or by endorsement, at the latest by May 2017, and conflicting national standards shall be

withdrawn at the latest by May 2017.

Attention is drawn to the possibility that some of the elements of this document may be the subject of

patent rights. CEN [and/or CENELEC] shall not be held responsible for identifying any or all such patent

rights.

According to the CEN-CENELEC Internal Regulations, the national standards organizations of the

following countries are bound to implement this European Standard: Austria, Belgium, Bulgaria,

Croatia, Cyprus, Czech Republic, Denmark, Estonia, Finland, Former Yugoslav Republic of Macedonia,

France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta,

Netherlands, Norway, Poland, Portugal, Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland,

Turkey and the United Kingdom.
Endorsement notice

The text of ISO 18391:2016 has been approved by CEN as EN ISO 18391:2016 without any modification.

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SIST EN ISO 18391:2017
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SIST EN ISO 18391:2017
INTERNATIONAL ISO
STANDARD 18391
First edition
2016-10-01
Geometrical product specifications
(GPS) — Population specification
Spécification géométrique des produits (GPS) — Spécification de
population
Reference number
ISO 18391:2016(E)
ISO 2016
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SIST EN ISO 18391:2017
ISO 18391:2016(E)
COPYRIGHT PROTECTED DOCUMENT
© ISO 2016, Published in Switzerland

All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized otherwise in any form

or by any means, electronic or mechanical, including photocopying, or posting on the internet or an intranet, without prior

written permission. Permission can be requested from either ISO at the address below or ISO’s member body in the country of

the requester.
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copyright@iso.org
www.iso.org
ii © ISO 2016 – All rights reserved
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SIST EN ISO 18391:2017
ISO 18391:2016(E)
Contents Page

Foreword ........................................................................................................................................................................................................................................iv

Introduction ..................................................................................................................................................................................................................................v

1 Scope ................................................................................................................................................................................................................................. 1

2 Normative references ...................................................................................................................................................................................... 1

3 Terms and definitions ..................................................................................................................................................................................... 1

4 Rules for establishing a population specification .............................................................................................................. 3

4.1 General ........................................................................................................................................................................................................... 3

4.2 Rules ................................................................................................................................................................................................................. 3

4.2.1 Rule 1: Description of a population specification................................................................................ 3

4.2.2 Rule 2: Description of type of individual GPS specification (univariate

or multivariate) ................................................................................................................................................................. 5

4.2.3 Rule 3 ......................................................................................................................................................................................... 7

5 Symbol used to specify a population specification ........................................................................................................... 8

6 Rules for indicating a population specification ................................................................................................................11

Annex A (informative) Relation in the GPS matrix model ...........................................................................................................15

Bibliography .............................................................................................................................................................................................................................16

© ISO 2016 – All rights reserved iii
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SIST EN ISO 18391:2017
ISO 18391:2016(E)
Foreword

ISO (the International Organization for Standardization) is a worldwide federation of national standards

bodies (ISO member bodies). The work of preparing International Standards is normally carried out

through ISO technical committees. Each member body interested in a subject for which a technical

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described in the ISO/IEC Directives, Part 1. In particular the different approval criteria needed for the

different types of ISO documents should be noted. This document was drafted in accordance with the

editorial rules of the ISO/IEC Directives, Part 2. www.iso.org/directives

Attention is drawn to the possibility that some of the elements of this document may be the subject of

patent rights. ISO shall not be held responsible for identifying any or all such patent rights. Details of

any patent rights identified during the development of the document will be in the Introduction and/or

on the ISO list of patent declarations received. www.iso.org/patents

Any trade name used in this document is information given for the convenience of users and does not

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For an explanation on the meaning of ISO specific terms and expressions related to conformity

assessment, as well as information about ISO’s adherence to the WTO principles in the Technical

Barriers to Trade (TBT), see the following URL: Foreword - Supplementary information

The committee responsible for this document is ISO/TC 213, Dimensional and geometrical product

specifications and verification.
iv © ISO 2016 – All rights reserved
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SIST EN ISO 18391:2017
ISO 18391:2016(E)
Introduction

This International Standard is a Geometrical Product Specification (GPS) standard and is to be regarded

as a global GPS standard (see ISO 14638). It influences all chain links of all chains of standards.

The ISO/GPS Masterplan given in ISO 14638 gives an overview of the ISO/GPS system of which this

document is a part. The fundamental rules of ISO/GPS given in ISO 8015 apply to this document and

the default decision rules given in ISO 14253-1 apply to specifications made in accordance with this

document, unless otherwise indicated. For more detailed information on the relationship of this

International standard to other standards and to the GPS matrix model, see Annex A.

In order to define the permissible interval for a geometrical characteristic, the designer only defines

a condition (a unilateral tolerance limit or a bilateral pair of tolerance limits) for each workpiece, by

considering the worst case impact in an assembly.

But when the tolerancing is based on a set of hypotheses about the population of the workpieces, one or

more additional requirements should be added to verify these hypotheses.

NOTE The intent of this International Standard is not to define calculation methods to determine tolerances,

but to give the means to express the hypotheses to verify.
© ISO 2016 – All rights reserved v
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SIST EN ISO 18391:2017
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SIST EN ISO 18391:2017
INTERNATIONAL STANDARD ISO 18391:2016(E)
Geometrical product specifications (GPS) — Population
specification
1 Scope

This International Standard defines rules to establish and to indicate population specifications, which

are used to specify conditions on population characteristics, which are established from a set of

characteristic values obtained one on each workpiece of a population of workpieces.

A population specification (as applied to a population of workpieces considered as a collection and

not as individual items) can be seen as a complementary requirement to the individual specification

(as applied to each workpiece considered as individual items). Population specifications express the

statistical hypotheses used on the population of workpieces.

NOTE 1 A population specification is a complement to an individual GPS specification.

NOTE 2 This International Standard is not intended to mandate a given tolerancing method or how to calculate

tolerance values. Its intent is to specify tools to allow the expression of population specifications.

2 Normative references

The following documents, in whole or in part, are normatively referenced in this document and are

indispensable for its application. For dated references, only the edition cited applies. For undated

references, the latest edition of the referenced document (including any amendments) applies.

ISO 1101, Geometrical product specifications (GPS) — Geometrical tolerancing — Tolerances of form,

orientation, location and run-out

ISO 14405-1, Geometrical product specifications (GPS) — Dimensional tolerancing — Part 1: Linear sizes

ISO 17450-1, Geometrical product specifications (GPS) — General concepts — Part 1: Model for geometrical

specification and verification
3 Terms and definitions

For the purposes of this document, the terms and definitions given in ISO 17450-1 and the following apply.

3.1
population characteristic

statistic defined from the characteristic values, obtained on the population of workpieces or the

population of assemblies

Note 1 to entry: Population characteristics are used to consider the population of workpieces.

Note 2 to entry: Population characteristics are only statistically meaningful when the values are based upon

global individual characteristics, see Example 2.

EXAMPLE 1 The arithmetic mean and the standard deviation of a global individual characteristic on the

population of workpieces, are population characteristics.
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EXAMPLE 2 The minimum circumscribed diameter has one unique value for a given cylindrical feature.

Therefore a population characteristic based on this individual characteristic value will be statistically

meaningful. The two-point diameter for a given cylindrical feature will vary within a range, dependent upon

the form deviations of the feature. In this case, one population characteristic for two-point diameter cannot be

defined from the population of values. However, it is possible to establish a population characteristic from the

maximum two point diameter along the geometric feature, which is a global individual characteristic, together

with a population characteristic from the minimum two-point diameter along the geometric feature which is

another global individual characteristic.
3.2
population condition
limit that applies to the population characteristic value

Note 1 to entry: Population conditions can be used for statistical process control (SPC).

EXAMPLE The mean value, µ, of the minimum circumscribed diameter of a population of workpieces can

be considered as a population characteristic, and required to be less than or equal to 10,1, which is a population

condition (see Clause 6).
3.3
statistic
completely specified function of random variables

[SOURCE: ISO 3534-1:2006, definition 1.8, modified — Notes have not been reproduced.]

Note 1 to entry: In GPS, the random variables, which are used are in most of cases one-dimensional (scalar).

Multi-dimensional (vector) variables also exist.

Note 2 to entry: For a population or a sample of individual characteristic values, at least one statistic can be

applied. In GPS, a statistic can be used on a population of local individual characteristic values taken on one

workpiece or, on a population of global individual characteristic values taken on a population of workpieces.

EXAMPLE See Table 1. More information can be found in ISO 3534- series.
Table 1 — Non exhaustive list of population statistics
Description of the statistic Mathematical description according to ISO 3534‑1
A) Minimum minimum (X)
B) Maximum maximum (X)
C) Mean: expected value
μ ==E()XX ,
i=1
 
or μ = Eg()X ==gX()ddpg()xF()x
  ∫∫
D) Mean deviation: difference between the mean
δμ=−τ
and the target value (τ)
E) Standard deviation
σ = VX()
F) Variance
 
 
VX() =−EX EX()
 
 
 
G) y % distribution quantile of the variable X
 
: Pyx ≤ = %
X X
y %  y%
 
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SIST EN ISO 18391:2017
ISO 18391:2016(E)
Table 1 (continued)
Description of the statistic Mathematical description according to ISO 3534‑1
H) Median, i.e 50 % distribution quantile
50%
I) Median absolute deviation from median
Δ with =−x
50 %
Δ X
50%
The symbols used in this table are defined in Table 2
Where X is the global characteristic value on one workpiece.
See Reference [6].
4 Rules for establishing a population specification
4.1 General

A population characteristic is a characteristic, which is calculated from a set of values, each of which is

an global individual characteristic value obtained on one workpiece of the population.

In some applications it is necessary to specify that one or more relations between the workpieces

of the population shall be satisfied. The following rules describe the implication on the individual

specification, and how to indicate a population specification.

A population characteristic can be used to manage statistical tolerancing requirements or the

implementation of statistical process control indexes.
4.2 Rules
4.2.1 Rule 1: Description of a population specification
4.2.1.1 Rule # 1a (indicating a population specification)

By default, a GPS specification is an individual specification. When a population specification is required

to complement an individual specification then the tolerance value of the individual GPS specification

shall be followed by the modifier .
4.2.1.2 Rule # 1b (individual characteristic)

To define a population characteristic, an individual specification shall be used to define an individual

signed global characteristic on each workpiece. In cases where the characteristic captures material

deviation, the positive direction is out of the material.
4.2.1.3 Rule # 1c (deriving a global characteristic from a local characteristic)

By default, if the GPS characteristic is a local characteristic, it shall be transformed in one or two global

characteristics by applying a rank order operator as defined in ISO 14405-1 ( , , , ,

, etc.). If no rank order operato
...

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