ISO/DIS 25935

ISO/TC 213

Secretariat: BSI

Date: 2025-12-17

Geometrical product specifications (GPS) — Restrained states

Spécifications géométriques des produits (GPS) — Etats contraints

DIS stage

© ISO 2025

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Contents

Foreword

Introduction

Scope

Normative references

Terms and definitions

Basic concept

Restrained state

General

Restraining conditions

Indication

General indications

Indication of specifications

Indication of restraining features

Indication of gravity

Indication of forces

(informative) Examples

(informative) Relationship to the GPS matrix model

Foreword

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This document was prepared by Technical Committee ISO/TC 213, Dimensional and geometrical product specifications and verification, collaboration with the European Committee for Standardization (CEN) Technical Committee CEN/TC 290, Dimensional and geometrical product specification and verification, in accordance with the Agreement on technical cooperation between ISO and CEN (Vienna Agreement).

This document cancels and replaces ISO 10579:2010, which has been technically revised. In addition to the change of number, the main changes to ISO 10579:2010 are as follows:

• New introduction of restrained states for specifying parts under external influences e.g., gravity, forces.
• More than one restrained state may be applied to one part.
• New introduction of graphical symbols and identifiers for indicating restrained states, gravity and force.

Introduction

This document is a geometrical product specification (GPS) standard and is to be regarded as a general GPS standard (see ISO 14638). It influences chain link A in the GPS matrix structure.

The ISO GPS matrix model 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 8015:2011 apply to this document and the default decision rules given in ISO 14253-1 apply to the specifications made in accordance with this document, unless otherwise indicated.

For more detailed information on the relation of this document to other standards and the GPS matrix model, see Annex B.

According to the rigid workpiece principle in ISO 8015:2011, all parts are by default considered rigid (i.e. having infinite stiffness) and all GPS specifications apply in a state undeformed by any external forces (in this document referred to as restraining conditions).

While the rigid workpiece principle applies well for many industrial cases, it is however inadequate in cases where the deformations (caused by e.g. contact with counterparts, gravity, forces, etc.) are non-negligible with respect to the part’s function. In such cases it is beneficial to specify the part in restrained state(s).

Geometrical product specifications (GPS) — Restrained states

This document specifies rules for restrained states.

The following documents are referred to in the text in such a way that some or all of their content constitutes requirements of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies.

ISO 128-2:2022, Technical product documentation (TPD) — General principles of representation — Part 2: Basic conventions for lines

ISO 1101:2017, Geometrical product specifications (GPS) — Geometrical tolerancing — Tolerances of form, orientation, location and run-out

ISO 5459:2024, Geometrical product specifications (GPS) — Geometrical tolerancing — Datums and datum systems

ISO 7499:2024, Technical product documentation (TPD) — Unique integral feature identification (UIFI)

ISO 8015:2011, Geometrical product specifications (GPS) — Fundamentals — Concepts, principles and rules

ISO 10209:2022, Technical product documentation — Vocabulary — Terms relating to technical drawings, product definition and related documentation

The Terms and definitions clause is a mandatory element of the text.

For rules on the drafting of the Terms and definitions, refer to the ISO/IEC Directives, Part 2:2021, Clause 16.

To insert a new terminological entry, go to the Structure tab and click on Insert Term entry.

For the purposes of this document, the following terms and definitions apply.

ISO and IEC maintain terminological databases for use in standardization at the following addresses:

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restrained part

part on which one or more restrained states are defined

Note 1 to entry: In the context of this document, “part” is to be interpreted in its broadest sense, equivalent to e.g. a component, a workpiece, an assembly

restrained state

state in which a part is restrained by one or more restraining conditions

restraining conditions

elements that are needed to fully restrain a part

Note 1 to entry: Note 1 to entry: Restraining conditions can be: restraining features, gravity, forces (non-exhaustive list).

restraining feature

ideal geometrical feature that is restraining a part

gravity

natural force by which objects with mass attract one another

force

physical quantity that causes an object to deform, accelerate or change its motion

technical product documentation TPD

means of conveying all or part of a design definition or specification of a product

[SOURCE: ISO 10209:2022, 3.10.163]

designer

professional conceptualizing, developing and documenting solutions to meet functional, geometrical and technical requirements by applying standards, principles and tools

Restrained state should be understood as a representation of a part in its applicable states, e.g. part in its functional or working state where it is deformed compared to its manufactured state, etc.

The decision whether to specify a part in restrained state(s) shall be made by the designer. This document does not provide rules for making such determination. Generally, a part should be specified in restrained state(s) when deformations caused by external factors (e.g. contact to counterparts, gravity, forces, etc.) are non-negligible with respect to the part’s function. This determination is not directly related to the material composition or mechanical properties of the part as such.

A restrained state is a result of all restraining conditions that apply in that state. See 5.2 Restraining conditions.

When defining a restrained state, the definition shall ensure mechanical equilibrium. For example, in cases where gravity is applied, the arrangement of restraining features shall ensure required support so that the definition does not result in a free-fall.

Datums and datum systems established on a part in a restrained state shall be established after having applied all the applicable restraining conditions that are defined for the given restrained state and according to ISO 5459:2024.

Each restrained state shall be given a name, constituting of “RS” and followed by a positive integer number, e.g. “RS1”. Multiple restrained states are possible for one part, hence “RS2”, “RS3”, etc. In cases of single restrained state on the TPD, the restrained state name may be simplified by omitting the integer number, hence stating only “RS”.

When specifying a part in a restrained state, all restraining conditions that apply in the given state shall be defined.

The restraining conditions are the following:

• restraining features (5.2.2)
• gravity (5.2.3)
• forces (5.2.4)
• other restraining conditions (5.2.5)

All restraining conditions shall be uniquely named, and it shall be indicated which restrained states they belong to. See 6.1 General indications.

By default, the sequence in which restraining conditions are applied is considered having no effect on the establishment of the resulting restrained state. In cases where the sequence is non-negligible, it shall be specified on the TPD. Means for specifying the sequence are not provided in this document. Such specification may be made by using e.g. notes, additional specification documents, company standards, etc.

Restraining features are geometrical features that are restraining a part in a restrained state. Restraining features shall be considered having ideal shape and size, and infinite stiffness. They shall be understood as a representation of restraining objects (e.g. counterpart).

The shape, size (if applicable), extent, and situation of restraining feature shall be fully defined on the TPD.

The definition of the situation of restraining features shall include:

• definition of situation within the collection (if applicable) of restraining features, and
• definition of situation of the (collection) of restraining features with respect to the restrained part.

According to the definition of situation, restraining features can be static or mobile. Forces may be applied on the restrained part through mobile restraining features. See 5.2.2.

Restraining features are not considered as datum features by default, however datums and datum systems can be established from them if needed and shall follow the rules of ISO 5459:2024.

All restraining features shall be in contact with the restrained part. In cases where during application the restraining feature(s) do not interface with the part as specified, the specification shall define how such situation shall be handled, e.g. by using notes, additional technical documentation, company-specific indications, etc.

The application of gravity shall be optional, provided it is required for the intended purpose. It shall only be specified in restrained states. Specification of gravity is non-applicable in the unrestrained state.

The decision whether to specify gravity shall be based on an assessment of the effect of gravity with respect to the part’s functional need in a given restrained state. Gravity should be specified if its effect is non-negligible and should not be specified when its effect is negligible.

Specification of gravity shall be made according to 6.4. Furthermore, the specification of gravity shall be complemented by necessary restraining features to prevent the part from falling.

In case of multiple restrained states, multiple specifications of gravity are possible.

The application of forces shall be optional, provided it is required for the intended purpose. Forces may be applied on movable restraining features or directly on the part’s surface.

The definition of a force shall include its situation and magnitude. See 6.5.

Additional restraining conditions that are needed to fully define a restrained state and that are other than restraining features (5.2.2), gravity (5.2.3), and forces (5.2.4), within the scope of this document are referred to as other restraining conditions. Such conditions can be but are not limited to: magnetic field, acceleration, volume forces, etc.

Specification of other restraining conditions is optional, and they may only be specified in restrained states. Such conditions should be specified if their affect is non-negligible with respect to the part’s functional need.

This document does not provide means to specify these conditions; such specification may be made by using e.g. notes on the TPD, references to additional technical documentation, company-specific indications, etc.

These conditions should be uniquely named and assigned to applicable restrained state(s), according to 6.1.

As part of definition of restrained state(s), a reference to ISO 25935 shall be made on a TPD. This reference is made by stating a note ISO 25935 , preferably close to the title block. See Figure 1.

The ISO 25935 note shall be followed by notes that define the restraining conditions. Notes for definition of restraining conditions shall be composed of a restrained state identifier followed by an “equals” sign and followed by the list of restraining conditions that apply for the given restrained state. Semicolon shall be used as a separator for listing the restraining conditions. See Figure 1.

Key

(a) (1) reference to ISO 25935

(b) (2) restraining conditions

(c) (3) TPD-default state

Figure 1 — General indication

A restrained state may optionally be set as a default restrained state on a TPD. To set the TPD default state, the ISO 25935 note shall be followed by the identifier of the applicable restrained state. See Figure 1.

If a TPD has a default restrained state defined, then all specifications shall apply in that state, unless indicated otherwise by explicit specifications.

Examples of restrained states indications are given in Annex A .

Restrained state identifier consists of a restrained state name in an oblong frame. See Figure 2.

Figure 2 — Restrained state identifier

Each specification that applies in a restrained state shall be indicated with a restrained state identifier. The restrained state identifiers shall be placed adjacent to the applicable specifications, according to ISO 1101:2017. See Figure 3.

Figure 3

Specifications that apply in restrained states

In cases where a restrained state is set as a TPD default state the restrained state identifiers for specifications that apply in that given state shall be omitted, see 6.1.

When there is no TPD default restrained state defined, the specifications without restrained state identifiers shall apply in an unrestrained state.

In cases where a restrained state is set as a TPD default state, the specifications that apply in an unrestrained state shall be indicated with an unrestrained state identifier. See Figure 4 and Figure 5.

Figure 4 — Unrestrained state identifier

Figure 5

Specifications with unrestrained state identifier

All restraining features shall be illustrated on the TPD, using a long-dashed double dotted narrow line according to ISO 128-2:2022 (Line type 05.1).

All restraining features shall be uniquely named and indicated according to ISO 7499:2024, e.g. “2A”, “4C”, etc.

The indication may include the applicable situation features of the restraining features, according to ISO 20223. See Figure 6.

Figure 6 — Indication of restraining features

Indication of gravity shall be made by using a gravity indicator, see Figure 7.

The gravity indication shall have a unique name, consisting of letter G and followed by a positive integer number, e.g. G1, G2, etc.

The gravity indicator shall include a straight line and an arrowhead. The straight line shall be used for referring to the direction of gravity. See Figure 7.

In cases where the location of gravity is non-negligible, the indicator shall additionally include a point. See Figure 8.

Figure 7 — Gravity indicator without location

Figure 8 — Gravity indicator with location

Indication of forces shall be made by using a force indicator, see Figure 9.

The force indicator shall include a straight line, an arrowhead, and optionally a point. The straight line shall be used for referring to the direction of force. The point shall be used for referring to the location of force, in cases where it is relevant.

The force indication shall have a unique name, consisting of letter F and followed by a positive integer number, e.g. F1, F2, etc. See Figure 9.

Figure 9 — Force indicator

1. 
   (informative)
   
   Examples

Examples of restrained state and its interpretation are given in Figure A.1 and Figure A.2.

Figure A.1 — Example 1

NOTE 1 Interpretation of information in figure A.1:

• In restrained state 1 (RS1), the part is situated on a planar restraining feature 2A and affected by gravity G1.
• In restrained state 2 (RS2), the part is restrained in a cylindrical restraining feature 3E. The effect of gravity is non-applicable (negligible) in this state.
• Relative mutual situation between the restraining features (2A and 3E) is not constrained, hence it is not indicated.
• RS1 is set as a default state, therefore specifications without RS identifier (specifications No. 1, 4, 5, and 6) apply in RS1.
• Specifications No. 2 and 3 apply in RS2.

Figure A.2 — Example 2

NOTE 2 Interpretation of information in figure A.2:

• In restrained state 1 (RS1), the part is restrained by all indicated restraining features and affected by gravity G1.
• In restrained state 2 (RS2), the part is restrained by all indicated restraining features except 2A3, and affected by gravity G1.
• All restraining features are constrained in mutual orientations and locations, according to the Note.
• Specifications with RS1 and RS2 identifiers apply in restrained states 1 and 2 respectively.

1. 
   (informative)
   
   Relationship to the GPS matrix model
   1. General

The ISO GPS matrix model given in ISO14638 gives an overview of the ISO GPS system of which this document is a part.

The fundamental rules of ISO GPS given in ISO8015 apply to this document and the default decision rules given in ISO14253-1 apply to specifications made in accordance with this document, unless otherwise indicated.

• 1. Information about this document and its use

This documente defines the terminology and concepts for restrained states.

• 1. Position in the GPS matrix model

This document is a general ISO GPS standard which influences chain links X and X of the chains of standards on feature properties and measurement in the GPS matrix model, as shown in Table B.1. The rules and principles given in this document apply to all segments of the ISO GPS matrix which are indicated with a filled dot (•). See Table B.1.

Table B.1

• 1. Related International Standards

The related International Standards are those of the chains of standards indicated in Table B.1.