Geometrical product specifications(GPS)—Geometrical tolerancing—Maximum material requirement(MMR),least material requirement(LMR)and reciprocity requirement(RPR)
Codeofchina.com is in charge of this English translation. In case of any doubt about the English translation, the Chinese original shall be considered authoritative.
This standard is developed in accordance with the rules given in GB/T 1.1-2009.
This standard replaces GB/T 16671-2009 Geometrical product specifications (GPS) - Geometrical tolerancing - Maximum material requirement (MMR), least material requirement (LMR) and reciprocity requirement (RPR). The following main technical changes have been made with respect to GB/T 16671-2009:
—— information about the reference documents and further interpretation for terms and definitions are added;
—— the scope limit of the feature of size applicable to this standard is added.
This standard has been redrafted and modified in relation to ISO 2692: 2014 Geometrical product specifications (GPS) - Geometrical tolerancing - Maximum material requirement (MMR), least material requirement (LMR) and reciprocity requirement (RPR).
Technical differences between this standard and ISO 2692: 2014 are marked with perpendicular single line (|) in the outside page margin of the provisions concerned. The corresponding technical deviations and their causes are as follows:
—— The adjustments of technical deviations are made for the normative references in this standard so as to adapt to the technical conditions of China. The adjustments are mainly reflected in clause 2 "Normative reference", which are detailed as follows:
• ISO 1101-2012 is replaced by GB/T 1182-2018 which is modified in relation to the former;
The following editorial changes have been made in this standard:
—— In informative Annex C, the matrix model given in ISO 14638: 1995 adopted in the original standard is changed to the new matrix model given in ISO 14638: 2015.
This standard was proposed by and is under the jurisdiction of National Technical Committee 240 on Geometrical Product Specifications of Standardization Administration of China.
The previous editions of this standard are as follows:
—— GB/T 16671-1996, and GB/T 16671-2009.
Geometrical product specifications (GPS) - Geometrical tolerancing - Maximum material requirement (MMR), least material requirement (LMR) and reciprocity requirement (RPR)
1 Scope
This standard defines the terms and definitions, basic requirements, drawings and application examples of the maximum material requirement, the least material requirement and the reciprocity requirement. These requirements can only be applied to features of size.
This standard is used to control specific functions of workpieces where size and geometry are interdependent, e.g. to fulfill the functions “assembly of parts” (for maximum material requirement) or “minimum wall thickness” (for least material requirement). However, the maximum material requirement and least material requirement are also used to fulfill other functional requirements.
Considering this interdependence between size and geometry, the principle of independency defined in GB/T 4249 does not apply when the maximum material requirement, least material requirement, or reciprocity requirement, are used.
2 Normative references
The following referenced documents are indispensable for the application 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.
GB/T 1182-2018 Geometrical product specifications (GPS) - Geometrical tolerances of form orientation location and run-out (ISO 1101: 2017, IDT)
GB/T 18780.2-2003 Geometrical product specifications (GPS) - Geometrical features - Part 2: Extracted median line of a cylinder and a cone, extracted median surface, local size of an extracted feature (ISO 14660-2: 1999, IDT)
ISO 5459: 2011 Geometrical product specifications (GPS) - Geometrical tolerancing - Datums and datum systems
ISO 14405-1: 2010 Geometrical product specifications (GPS) - Dimensional tolerancing - Part 1: Linear sizes
ISO 17450-1: 2011 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 in GB/T 18780.2-2003, ISO 5459: 2011, ISO 14405-1: 2010, and ISO 17450-1: 2011 and the following apply.
3.1
integral feature
geometrical feature belonging to the real surface of the workpiece or to a surface model
Note 1: An integral feature is intrinsically defined, e.g. skin of the workpiece.
Note 2: Adapted from ISO 17450-1: 2011, definition 3.3.5.
3.2
feature of size
feature of linear size
geometrical feature, having one or more intrinsic characteristics, only one of which may be considered as variable parameter, that additionally is a member of a “one parameter family”, and obeys the monotonic containment property for that parameter
Note 1: Adapted from ISO 17450-1:2011, definition 3.3.1.5.1. See also ISO 22432: 2011, definitions 3.2.5.1.1.1 and 3.2.5.1.1.2 for “one parameter family” and “monotonic containment property”.
Example 1: A single cylindrical hole or shaft is a feature of linear size. Its linear size is its diameter.
Example 2: Two opposite parallel plane surfaces are a feature of linear size. Its linear size is the distance between the two parallel planes.
3.3
derived feature
geometrical feature, which does not exist physically on the real surface of the workpiece and which is not natively a nominal integral feature
Note 1: A derived feature can be established from a nominal feature, an associated feature, or an extracted feature. It is qualified respectively as a nominal derived feature, an associated derived feature, or an extracted derived feature.
Note 2: The centre point, the median line and the median surface defined from one or more integral features are types of derived features.
Note 3: Adapted from ISO 17450-1: 2011, definition 3.3.6.
Example 1: The median line of a cylinder is a derived feature obtained from the cylinder surface, which is an integral feature. The axis of the nominal cylinder is a nominal derived feature.
Example 2: The median surface of two opposite parallel plane surfaces is a derived feature obtained from the two parallel plane surfaces, which constitute an integral feature. The median plane of the nominal two opposite parallel planes is a nominal derived feature.
3.4
maximum material condition
MMC
state of the considered extracted feature, where the feature of size is at that limit of size where the material of the feature is at its maximum everywhere (maximum material), e.g. minimum hole diameter and maximum shaft diameter
Note 1: The term maximum material condition, MMC, is used in this standard to indicate, at ideal or nominal feature level (see ISO 17450-1: 2011), which limit of the requirement (upper or lower) is concerned.
Note 2: The size of the extracted feature at maximum material condition, MMC, can be defined by default, or by several special definitions of the size of the extracted feature (see ISO 14405-1: 2010).
Note 3: The maximum material condition, MMC, as defined in this standard, can be used unambiguously with any definition of size of the extracted feature.
3.5
maximum material size
MMS
dimension defining the maximum material condition of a feature
Note 1: Maximum material size, MMS, can be defined by default or by one of several special definitions of the size of the extracted feature (see ISO 14405-1: 2010 and GB/T 18780.2-2003).
Note 2: In this standard, maximum material size, MMS, is used as a numerical value, therefore no specific definition of the extracted size is needed to permit unambiguous use of maximum material size, MMS.
Note 3: See Annex A.
3.6
least material condition
LMC
state of the considered extracted feature, where the feature of size is at that limit of size where the material of the feature is at its minimum everywhere, e.g. maximum hole diameter and minimum shaft diameter
Note 1: The term least material condition, LMC, is used in this standard to indicate, at the ideal or nominal feature level (see ISO 17450-1: 2011), which limit of the requirement (upper or lower) is concerned.
Note 2: The size at least material condition, LMC, can be defined by default or by several special definitions of the size of extracted feature (see ISO 14405-1: 2010).
Note 3: The least material condition, LMC, as defined in this standard, can be used unambiguously with any definition of size of the extracted feature.
3.7
least material size
LMS
dimension defining the least material condition of a feature
Note 1: Least material size, LMS, can be defined by default or by one of several special definitions of the size of the extracted feature (see ISO 14405-1: 2010 and GB/T 18780.2-2003).
Note 2: In this standard, least material size, LMS, is used as a numerical value, therefore no specific definition of the extracted size is needed to permit unambiguous use of least material size, LMS.
Note 3: See Annex A.
3.8
maximum material virtual size
MMVS
size generated by the collective effect of the maximum material size, MMS, of a feature of size and the geometrical tolerance (form, orientation or location) given for the derived feature of the same feature of size
Note 1: Maximum material virtual size, MMVS, is a parameter for size used as a numerical value connected to maximum material virtual condition, MMVC.
Note 2: For external features, MMVS is the sum of MMS and the geometrical tolerance, whereas for internal features, it is the difference between MMS and the geometrical tolerance.
Note 3: The MMVS for external features of size, lMMVS,e, is given by Formula (1):
lMMVS,e=lMMS+δ (1)
and the MMVS for internal features of size, lMMVS,i, is given by Formula (2):
lMMVS,i=lMMS-δ (2)
where,
lMMS—— the maximum material size;
δ—— the geometrical tolerance.
3.9
maximum material virtual condition
MMVC
state of associated feature of maximum material virtual size, MMVS
Note 1: Maximum material virtual condition, MMVC, is a perfect form condition of the feature.
Note 2: Maximum material virtual condition, MMVC, includes an orientation constraint (in accordance with GB/T 1182-2018 and ISO 5459: 2011) of the associated feature when the geometrical tolerance is an orientation tolerance (see Figure A.3). Maximum material virtual condition, MMVC, includes a location constraint (in accordance with GB/T 1182-2018 and ISO 5459: 2011) of the associated feature when the geometrical specification is a location specification (see Figure A.4).
Note 3: See Figures A.1-A.4, A.6. A.7 and A.10-A.13.
3.10
least material virtual size
LMVS
size generated by the collective effect of the least material size, LMS, of a feature of size and the geometrical tolerance (form, orientation or location) given for the derived feature of the same feature of size
Note 1: Least material virtual size, LMVS, is a parameter for size used as a numerical value connected to least material virtual condition, LMVC.
Note 2: For external features, LMVS is the difference between LMS and the geometrical tolerance, whereas for internal features, it is the sum of LMS and the geometrical tolerance.
Note 3: The LMVS for external features of size, lLMVS,e, is given by Formula (3):
lLMVS,e=lLMS-δ (3)
and the LMVS for internal features of size, lLMCS,i, is given by Formula (4):
lLMVS,i=lLMS+δ (4)
where,
lLMS—— the least material size;
δ—— the geometrical tolerance.
3.11
least material virtual condition
LMVC
state of associated feature of least material virtual size, LMVS
Note 1: Least material virtual condition, LMVC, is a perfect form condition of the feature.
Note 2: Least material virtual condition, LMVC, includes an orientation constraint (in accordance with GB/T 1182-2018 and ISO 5459) of the associated feature when the geometrical tolerance is an orientation specification. Least material virtual condition, LMVC, includes a location constraint (in accordance with GB/T 1182-2018 and ISO 5459) of the associated feature when the geometrical tolerance is a location specification (see Figure A.5).
Note 3: see Figures A.5, A.8 and A.9.
3.12
maximum material requirement
MMR
requirement for a feature of size that its maximum material virtual condition, MMVC, shall not be violated by its non-ideal feature, i.e. its non-ideal feature shall not exceed its maximum material virtual boundary, MMVB
Its maximum material virtual condition, MMVC, or maximum material virtual boundary is the limit state of a geometrical feature of the same type and of perfect form with the toleranced feature of size, and the size at such limit state is MMVS.
Note 1: Maximum material requirement, MMR, is used to control the assemblability of a workpiece.
Note 2: See also 4.2.
3.13
least material requirement
LMR
requirement for a feature of size that its least material virtual condition, LMVC, shall not be violated by its non-ideal feature, i.e. its non-ideal feature shall not exceed its least material virtual condition, LMVB
Note 1: Least material requirements, LMR, are used in pairs, e.g. to control the minimum wall thickness between two symmetrical or coaxially located similar features of size.
Note 2: See also 4.3.
3.14
reciprocity requirement
RPR
additional requirement for a feature of size used as an addition to the maximum material requirement, MMR, or the least material requirement, LMR, to indicate that the size tolerance is increased by the difference between the geometrical tolerance and the actual geometrical deviation
4 Maximum material requirement, MMR and least material requirement, LMR
4.1 General
The maximum material requirement, MMR, and the least material requirement, LMR, can be applied to a set of one or more feature(s) of size as toleranced feature(s), or datum(s), or both. They create a combined requirement between the size of feature(s) of size and the geometry requirements (form, orientation or location) specified for its (their) derived feature(s).
Note 1: This edition of this standard only covers features of size of type cylinder and type two opposite parallel plane surfaces. Consequently, the only possible derived features are median lines and median surfaces.
Note 2: In ISO GPS standards, threaded features are often considered as features of size of type cylinder. However, no rules are defined in this standard for how to apply MMR, LMR and RPR to threaded features. Consequently, the tools defined in this standard cannot be used for threaded features.
When maximum material requirement, MMR, or least material requirement, LMR, is used, the two specifications (size specification and geometrical specification) are transformed into one collective requirements specification. The collective specification concerns only the integral feature, which in this standard relates to the surface(s) of the feature(s) of size(s).
Note 3: In the past, the maximum material requirement, MMR, was referred to as the maximum material principle, MMP.
When no modifiers ( , and ) are applied to the toleranced feature, the definitions of size of extracted feature in ISO 14405-1: 2010 and GB/T 18780.2-2003 apply.
When no modifiers ( , ) are applied to the datum, ISO 5459: 2011 applies. The modifier does not apply to datums.
4.2 Maximum material requirement, MMR
4.2.1 Maximum material requirement for toleranced features
The maximum material requirement for toleranced features results in four independent requirements:
— a requirement for the upper limit of the local size [see Rules A 1) and A 2)];
— a requirement for the lower limit of the local size [see Rules B 1) and B 2)];
— a requirement for the surface non-violation of the MMVC (see Rule C);
— a requirement when more than one feature is involved (see Rule D).
When the maximum material requirement, MMR, applies to the toleranced feature, it shall be indicated on drawings by the symbol placed after the geometrical tolerance of the derived feature of the feature of size (toleranced feature) in the tolerance indicator.
In this case, it specifies for the surface(s) (of the feature of size) the following rules.
a) Rule A The extracted local sizes of the toleranced feature shall be:
1) equal to or smaller than the maximum material size, MMS, for external features;
2) equal to or larger than the maximum material size, MMS, for internal features.
Note 1: This rule can be altered by the indication of reciprocity requirement, RPR, with the symbol after the symbol (see Clause 5 and Figure A.1).
b) Rule B The extracted local sizes of the toleranced feature shall be:
1) equal to or larger than the least material size, LMS, for external features [see Figures A.2 a), A.3 a), A.4 a), A.6 a), A.7 a), A.10 and A.11];
2) equal to or smaller than the least material size, LMS, for internal features [see Figures A.2 b), A.3 b), A.4 b), A.6 b), A.7 b), A.10 and A.11].
c) Rule C The maximum material virtual condition, MMVC, of the toleranced feature shall not be violated by the extracted integral feature (see Figures A.2, A.3, A.4, A.6, A.7, A.10 and A.11).
Note 2: Use of the envelope requirement (previously also known as the Taylor Principle) usually leads to superfluous constraints regarding the function of the feature(s) (assembleability). Use of such constraints and size definitions reduces the technical and economic advantage of maximum material requirement, MMR.
Note 3: When the geometric tolerance is from tolerance, the indication 0 has the same meaning as .
d) Rule D When the geometrical specification is an orientation or a location relative to a (primary) datum or a datum system, the maximum material virtual condition, MMVC, of the toleranced feature shall be in theoretically exact orientation or location relative to the datum or the datum system, in accordance with GB/T 1182-2018 and ISO 5459: 2011 (see 3.9 Note 2: and Figures A.3, A.4, A.6, and A.7). Moreover, in the case of several toleranced features controlled by the same tolerance indication, the maximum material virtual conditions, MMVCs, shall also be in theoretically exact orientation and location relative to each other in addition to the possible constraints relative to the datum(s) (see Figures A.1, A.10, A.11 and A.13).
Note 4: In the case of several toleranced features controlled by the same toleranced indication, the maximum material requirement, MMR, without any other modifier than has exactly the same meaning as the same requirement with both and CZ modifiers. To specify requirements that apply separately, the SZ modifier shall be used after the modifier .
4.2.2 Maximum material requirement for related datum features
The maximum material requirement for datum features results in three independent requirements:
— a requirement for the surface non-violation of the MMVC (see Rule E);
— a requirement for MMS when there is no geometrical specification or when there is only geometrical specifications whose tolerance value is not followed by the symbol (see Rule F);
— a requirement for MMS when there is a geometrical specification whose tolerance value is followed by the symbol and whose “datum” section (third and subsequent compartments) of the tolerance indicator meets a property defined in Rule G.
When the maximum material requirement, MMR, applies to the datum feature, it shall be indicated on drawings by the symbol placed after the datum letter(s) in the tolerance indicator.
Note 1: The use of after the datum letter is only possible if the datum is obtained from a feature of size.
Note 2: When maximum or least material requirement applies to all elements of the collection of surfaces of a common datum, the corresponding sequence of letters identifying the common datum are indicated within parentheses (see Figure A.13 and ISO 5459: 2011, Rule 9) and maximum material virtual conditions, MMVCs, are by default constrained in location and orientation relative to each other (see ISO 5459: 2011, Rule 7). When maximum or least material requirement applies only to one surface of the collection of features involved in a common datum, the sequence of letters identifying the common datum is not indicated within parentheses, and the requirement applies only to the feature identified by the letter placed just before the modifier.
In this case, it specifies for the surface(s) (of the feature of size) the following rules.
a) Rule E The maximum material virtual condition, MMVC, of the related datum feature shall not be violated by the extracted integral datum feature (see Figures A.6 and A.7).
b) Rule F The size of the maximum material virtual condition, MMVC, of the related datum feature shall be the maximum material size, MMS, when the related datum feature has no geometrical specification (see Figure A.6), or has only geometrical specifications whose tolerance value is not followed by the symbol , or has no geometrical specification complying with Rule G.
Note 3: In these cases, the MMVS for external and internal features of size, lMMVS, is given by Formula (5):
lMMVS=lMMS+0=lMMS (5)
where, lMMS is the maximum material size.
c) Rule G The size of the maximum material virtual condition, MMVC, of the related datum feature shall be the maximum material size, MMS, plus (for external features of size) or minus (for internal features of size) the geometrical tolerance, when the datum feature is controlled by a geometrical specification with the following properties:
1) its tolerance value is followed by the symbol , and
i) it is a form specification and the related datum corresponds to the primary datum of the tolerance indicator where the symbol is indicated next to the datum letter (see Figure A.7), or
ii) is an orientation/location specification whose datum or datum system contains exactly the same datum(s) in the same order as the one(s) called before the related datum in the tolerance indicator where the symbol is indicated next to the datum letter (see Figures A.12 and A.13).
Note 4: In this case, the MMVS for external features of size is as given in Formula (1), and the MMVS for internal features of size is as given in Formula (2). See 3.8, Note 3.
Note 5: When above properties are not observed, Rule F applies.
In the case of Rule G, the datum feature indicator shall be directly connected to that geometrical tolerance indicator from which maximum material virtual condition, MMVC, of the datum feature is controlled (see ISO 5459: 2011, Rule 1, dash 2)
Foreword i
1 Scope
2 Normative references
3 Terms and definitions
4 Maximum material requirement, MMR and least material requirement, LMR
5 Reciprocity requirement, RPR
Annex A (Informative) Examples of tolerancing with , and
Annex B (Informative) Concept diagram
Annex C (Informative) Location in the GPS matrix model
Bibliography
GB/T 16671-2018 Geometrical product specifications(GPS)—Geometrical tolerancing—Maximum material requirement(MMR),least material requirement(LMR)and reciprocity requirement(RPR) (English Version)
Standard No.
GB/T 16671-2018
Status
valid
Language
English
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PDF
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16500 words
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Detail of GB/T 16671-2018
Standard No.
GB/T 16671-2018
English Name
Geometrical product specifications(GPS)—Geometrical tolerancing—Maximum material requirement(MMR),least material requirement(LMR)and reciprocity requirement(RPR)
Codeofchina.com is in charge of this English translation. In case of any doubt about the English translation, the Chinese original shall be considered authoritative.
This standard is developed in accordance with the rules given in GB/T 1.1-2009.
This standard replaces GB/T 16671-2009 Geometrical product specifications (GPS) - Geometrical tolerancing - Maximum material requirement (MMR), least material requirement (LMR) and reciprocity requirement (RPR). The following main technical changes have been made with respect to GB/T 16671-2009:
—— information about the reference documents and further interpretation for terms and definitions are added;
—— the scope limit of the feature of size applicable to this standard is added.
This standard has been redrafted and modified in relation to ISO 2692: 2014 Geometrical product specifications (GPS) - Geometrical tolerancing - Maximum material requirement (MMR), least material requirement (LMR) and reciprocity requirement (RPR).
Technical differences between this standard and ISO 2692: 2014 are marked with perpendicular single line (|) in the outside page margin of the provisions concerned. The corresponding technical deviations and their causes are as follows:
—— The adjustments of technical deviations are made for the normative references in this standard so as to adapt to the technical conditions of China. The adjustments are mainly reflected in clause 2 "Normative reference", which are detailed as follows:
• ISO 1101-2012 is replaced by GB/T 1182-2018 which is modified in relation to the former;
The following editorial changes have been made in this standard:
—— In informative Annex C, the matrix model given in ISO 14638: 1995 adopted in the original standard is changed to the new matrix model given in ISO 14638: 2015.
This standard was proposed by and is under the jurisdiction of National Technical Committee 240 on Geometrical Product Specifications of Standardization Administration of China.
The previous editions of this standard are as follows:
—— GB/T 16671-1996, and GB/T 16671-2009.
Geometrical product specifications (GPS) - Geometrical tolerancing - Maximum material requirement (MMR), least material requirement (LMR) and reciprocity requirement (RPR)
1 Scope
This standard defines the terms and definitions, basic requirements, drawings and application examples of the maximum material requirement, the least material requirement and the reciprocity requirement. These requirements can only be applied to features of size.
This standard is used to control specific functions of workpieces where size and geometry are interdependent, e.g. to fulfill the functions “assembly of parts” (for maximum material requirement) or “minimum wall thickness” (for least material requirement). However, the maximum material requirement and least material requirement are also used to fulfill other functional requirements.
Considering this interdependence between size and geometry, the principle of independency defined in GB/T 4249 does not apply when the maximum material requirement, least material requirement, or reciprocity requirement, are used.
2 Normative references
The following referenced documents are indispensable for the application 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.
GB/T 1182-2018 Geometrical product specifications (GPS) - Geometrical tolerances of form orientation location and run-out (ISO 1101: 2017, IDT)
GB/T 18780.2-2003 Geometrical product specifications (GPS) - Geometrical features - Part 2: Extracted median line of a cylinder and a cone, extracted median surface, local size of an extracted feature (ISO 14660-2: 1999, IDT)
ISO 5459: 2011 Geometrical product specifications (GPS) - Geometrical tolerancing - Datums and datum systems
ISO 14405-1: 2010 Geometrical product specifications (GPS) - Dimensional tolerancing - Part 1: Linear sizes
ISO 17450-1: 2011 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 in GB/T 18780.2-2003, ISO 5459: 2011, ISO 14405-1: 2010, and ISO 17450-1: 2011 and the following apply.
3.1
integral feature
geometrical feature belonging to the real surface of the workpiece or to a surface model
Note 1: An integral feature is intrinsically defined, e.g. skin of the workpiece.
Note 2: Adapted from ISO 17450-1: 2011, definition 3.3.5.
3.2
feature of size
feature of linear size
geometrical feature, having one or more intrinsic characteristics, only one of which may be considered as variable parameter, that additionally is a member of a “one parameter family”, and obeys the monotonic containment property for that parameter
Note 1: Adapted from ISO 17450-1:2011, definition 3.3.1.5.1. See also ISO 22432: 2011, definitions 3.2.5.1.1.1 and 3.2.5.1.1.2 for “one parameter family” and “monotonic containment property”.
Example 1: A single cylindrical hole or shaft is a feature of linear size. Its linear size is its diameter.
Example 2: Two opposite parallel plane surfaces are a feature of linear size. Its linear size is the distance between the two parallel planes.
3.3
derived feature
geometrical feature, which does not exist physically on the real surface of the workpiece and which is not natively a nominal integral feature
Note 1: A derived feature can be established from a nominal feature, an associated feature, or an extracted feature. It is qualified respectively as a nominal derived feature, an associated derived feature, or an extracted derived feature.
Note 2: The centre point, the median line and the median surface defined from one or more integral features are types of derived features.
Note 3: Adapted from ISO 17450-1: 2011, definition 3.3.6.
Example 1: The median line of a cylinder is a derived feature obtained from the cylinder surface, which is an integral feature. The axis of the nominal cylinder is a nominal derived feature.
Example 2: The median surface of two opposite parallel plane surfaces is a derived feature obtained from the two parallel plane surfaces, which constitute an integral feature. The median plane of the nominal two opposite parallel planes is a nominal derived feature.
3.4
maximum material condition
MMC
state of the considered extracted feature, where the feature of size is at that limit of size where the material of the feature is at its maximum everywhere (maximum material), e.g. minimum hole diameter and maximum shaft diameter
Note 1: The term maximum material condition, MMC, is used in this standard to indicate, at ideal or nominal feature level (see ISO 17450-1: 2011), which limit of the requirement (upper or lower) is concerned.
Note 2: The size of the extracted feature at maximum material condition, MMC, can be defined by default, or by several special definitions of the size of the extracted feature (see ISO 14405-1: 2010).
Note 3: The maximum material condition, MMC, as defined in this standard, can be used unambiguously with any definition of size of the extracted feature.
3.5
maximum material size
MMS
dimension defining the maximum material condition of a feature
Note 1: Maximum material size, MMS, can be defined by default or by one of several special definitions of the size of the extracted feature (see ISO 14405-1: 2010 and GB/T 18780.2-2003).
Note 2: In this standard, maximum material size, MMS, is used as a numerical value, therefore no specific definition of the extracted size is needed to permit unambiguous use of maximum material size, MMS.
Note 3: See Annex A.
3.6
least material condition
LMC
state of the considered extracted feature, where the feature of size is at that limit of size where the material of the feature is at its minimum everywhere, e.g. maximum hole diameter and minimum shaft diameter
Note 1: The term least material condition, LMC, is used in this standard to indicate, at the ideal or nominal feature level (see ISO 17450-1: 2011), which limit of the requirement (upper or lower) is concerned.
Note 2: The size at least material condition, LMC, can be defined by default or by several special definitions of the size of extracted feature (see ISO 14405-1: 2010).
Note 3: The least material condition, LMC, as defined in this standard, can be used unambiguously with any definition of size of the extracted feature.
3.7
least material size
LMS
dimension defining the least material condition of a feature
Note 1: Least material size, LMS, can be defined by default or by one of several special definitions of the size of the extracted feature (see ISO 14405-1: 2010 and GB/T 18780.2-2003).
Note 2: In this standard, least material size, LMS, is used as a numerical value, therefore no specific definition of the extracted size is needed to permit unambiguous use of least material size, LMS.
Note 3: See Annex A.
3.8
maximum material virtual size
MMVS
size generated by the collective effect of the maximum material size, MMS, of a feature of size and the geometrical tolerance (form, orientation or location) given for the derived feature of the same feature of size
Note 1: Maximum material virtual size, MMVS, is a parameter for size used as a numerical value connected to maximum material virtual condition, MMVC.
Note 2: For external features, MMVS is the sum of MMS and the geometrical tolerance, whereas for internal features, it is the difference between MMS and the geometrical tolerance.
Note 3: The MMVS for external features of size, lMMVS,e, is given by Formula (1):
lMMVS,e=lMMS+δ (1)
and the MMVS for internal features of size, lMMVS,i, is given by Formula (2):
lMMVS,i=lMMS-δ (2)
where,
lMMS—— the maximum material size;
δ—— the geometrical tolerance.
3.9
maximum material virtual condition
MMVC
state of associated feature of maximum material virtual size, MMVS
Note 1: Maximum material virtual condition, MMVC, is a perfect form condition of the feature.
Note 2: Maximum material virtual condition, MMVC, includes an orientation constraint (in accordance with GB/T 1182-2018 and ISO 5459: 2011) of the associated feature when the geometrical tolerance is an orientation tolerance (see Figure A.3). Maximum material virtual condition, MMVC, includes a location constraint (in accordance with GB/T 1182-2018 and ISO 5459: 2011) of the associated feature when the geometrical specification is a location specification (see Figure A.4).
Note 3: See Figures A.1-A.4, A.6. A.7 and A.10-A.13.
3.10
least material virtual size
LMVS
size generated by the collective effect of the least material size, LMS, of a feature of size and the geometrical tolerance (form, orientation or location) given for the derived feature of the same feature of size
Note 1: Least material virtual size, LMVS, is a parameter for size used as a numerical value connected to least material virtual condition, LMVC.
Note 2: For external features, LMVS is the difference between LMS and the geometrical tolerance, whereas for internal features, it is the sum of LMS and the geometrical tolerance.
Note 3: The LMVS for external features of size, lLMVS,e, is given by Formula (3):
lLMVS,e=lLMS-δ (3)
and the LMVS for internal features of size, lLMCS,i, is given by Formula (4):
lLMVS,i=lLMS+δ (4)
where,
lLMS—— the least material size;
δ—— the geometrical tolerance.
3.11
least material virtual condition
LMVC
state of associated feature of least material virtual size, LMVS
Note 1: Least material virtual condition, LMVC, is a perfect form condition of the feature.
Note 2: Least material virtual condition, LMVC, includes an orientation constraint (in accordance with GB/T 1182-2018 and ISO 5459) of the associated feature when the geometrical tolerance is an orientation specification. Least material virtual condition, LMVC, includes a location constraint (in accordance with GB/T 1182-2018 and ISO 5459) of the associated feature when the geometrical tolerance is a location specification (see Figure A.5).
Note 3: see Figures A.5, A.8 and A.9.
3.12
maximum material requirement
MMR
requirement for a feature of size that its maximum material virtual condition, MMVC, shall not be violated by its non-ideal feature, i.e. its non-ideal feature shall not exceed its maximum material virtual boundary, MMVB
Its maximum material virtual condition, MMVC, or maximum material virtual boundary is the limit state of a geometrical feature of the same type and of perfect form with the toleranced feature of size, and the size at such limit state is MMVS.
Note 1: Maximum material requirement, MMR, is used to control the assemblability of a workpiece.
Note 2: See also 4.2.
3.13
least material requirement
LMR
requirement for a feature of size that its least material virtual condition, LMVC, shall not be violated by its non-ideal feature, i.e. its non-ideal feature shall not exceed its least material virtual condition, LMVB
Note 1: Least material requirements, LMR, are used in pairs, e.g. to control the minimum wall thickness between two symmetrical or coaxially located similar features of size.
Note 2: See also 4.3.
3.14
reciprocity requirement
RPR
additional requirement for a feature of size used as an addition to the maximum material requirement, MMR, or the least material requirement, LMR, to indicate that the size tolerance is increased by the difference between the geometrical tolerance and the actual geometrical deviation
4 Maximum material requirement, MMR and least material requirement, LMR
4.1 General
The maximum material requirement, MMR, and the least material requirement, LMR, can be applied to a set of one or more feature(s) of size as toleranced feature(s), or datum(s), or both. They create a combined requirement between the size of feature(s) of size and the geometry requirements (form, orientation or location) specified for its (their) derived feature(s).
Note 1: This edition of this standard only covers features of size of type cylinder and type two opposite parallel plane surfaces. Consequently, the only possible derived features are median lines and median surfaces.
Note 2: In ISO GPS standards, threaded features are often considered as features of size of type cylinder. However, no rules are defined in this standard for how to apply MMR, LMR and RPR to threaded features. Consequently, the tools defined in this standard cannot be used for threaded features.
When maximum material requirement, MMR, or least material requirement, LMR, is used, the two specifications (size specification and geometrical specification) are transformed into one collective requirements specification. The collective specification concerns only the integral feature, which in this standard relates to the surface(s) of the feature(s) of size(s).
Note 3: In the past, the maximum material requirement, MMR, was referred to as the maximum material principle, MMP.
When no modifiers ( , and ) are applied to the toleranced feature, the definitions of size of extracted feature in ISO 14405-1: 2010 and GB/T 18780.2-2003 apply.
When no modifiers ( , ) are applied to the datum, ISO 5459: 2011 applies. The modifier does not apply to datums.
4.2 Maximum material requirement, MMR
4.2.1 Maximum material requirement for toleranced features
The maximum material requirement for toleranced features results in four independent requirements:
— a requirement for the upper limit of the local size [see Rules A 1) and A 2)];
— a requirement for the lower limit of the local size [see Rules B 1) and B 2)];
— a requirement for the surface non-violation of the MMVC (see Rule C);
— a requirement when more than one feature is involved (see Rule D).
When the maximum material requirement, MMR, applies to the toleranced feature, it shall be indicated on drawings by the symbol placed after the geometrical tolerance of the derived feature of the feature of size (toleranced feature) in the tolerance indicator.
In this case, it specifies for the surface(s) (of the feature of size) the following rules.
a) Rule A The extracted local sizes of the toleranced feature shall be:
1) equal to or smaller than the maximum material size, MMS, for external features;
2) equal to or larger than the maximum material size, MMS, for internal features.
Note 1: This rule can be altered by the indication of reciprocity requirement, RPR, with the symbol after the symbol (see Clause 5 and Figure A.1).
b) Rule B The extracted local sizes of the toleranced feature shall be:
1) equal to or larger than the least material size, LMS, for external features [see Figures A.2 a), A.3 a), A.4 a), A.6 a), A.7 a), A.10 and A.11];
2) equal to or smaller than the least material size, LMS, for internal features [see Figures A.2 b), A.3 b), A.4 b), A.6 b), A.7 b), A.10 and A.11].
c) Rule C The maximum material virtual condition, MMVC, of the toleranced feature shall not be violated by the extracted integral feature (see Figures A.2, A.3, A.4, A.6, A.7, A.10 and A.11).
Note 2: Use of the envelope requirement (previously also known as the Taylor Principle) usually leads to superfluous constraints regarding the function of the feature(s) (assembleability). Use of such constraints and size definitions reduces the technical and economic advantage of maximum material requirement, MMR.
Note 3: When the geometric tolerance is from tolerance, the indication 0 has the same meaning as .
d) Rule D When the geometrical specification is an orientation or a location relative to a (primary) datum or a datum system, the maximum material virtual condition, MMVC, of the toleranced feature shall be in theoretically exact orientation or location relative to the datum or the datum system, in accordance with GB/T 1182-2018 and ISO 5459: 2011 (see 3.9 Note 2: and Figures A.3, A.4, A.6, and A.7). Moreover, in the case of several toleranced features controlled by the same tolerance indication, the maximum material virtual conditions, MMVCs, shall also be in theoretically exact orientation and location relative to each other in addition to the possible constraints relative to the datum(s) (see Figures A.1, A.10, A.11 and A.13).
Note 4: In the case of several toleranced features controlled by the same toleranced indication, the maximum material requirement, MMR, without any other modifier than has exactly the same meaning as the same requirement with both and CZ modifiers. To specify requirements that apply separately, the SZ modifier shall be used after the modifier .
4.2.2 Maximum material requirement for related datum features
The maximum material requirement for datum features results in three independent requirements:
— a requirement for the surface non-violation of the MMVC (see Rule E);
— a requirement for MMS when there is no geometrical specification or when there is only geometrical specifications whose tolerance value is not followed by the symbol (see Rule F);
— a requirement for MMS when there is a geometrical specification whose tolerance value is followed by the symbol and whose “datum” section (third and subsequent compartments) of the tolerance indicator meets a property defined in Rule G.
When the maximum material requirement, MMR, applies to the datum feature, it shall be indicated on drawings by the symbol placed after the datum letter(s) in the tolerance indicator.
Note 1: The use of after the datum letter is only possible if the datum is obtained from a feature of size.
Note 2: When maximum or least material requirement applies to all elements of the collection of surfaces of a common datum, the corresponding sequence of letters identifying the common datum are indicated within parentheses (see Figure A.13 and ISO 5459: 2011, Rule 9) and maximum material virtual conditions, MMVCs, are by default constrained in location and orientation relative to each other (see ISO 5459: 2011, Rule 7). When maximum or least material requirement applies only to one surface of the collection of features involved in a common datum, the sequence of letters identifying the common datum is not indicated within parentheses, and the requirement applies only to the feature identified by the letter placed just before the modifier.
In this case, it specifies for the surface(s) (of the feature of size) the following rules.
a) Rule E The maximum material virtual condition, MMVC, of the related datum feature shall not be violated by the extracted integral datum feature (see Figures A.6 and A.7).
b) Rule F The size of the maximum material virtual condition, MMVC, of the related datum feature shall be the maximum material size, MMS, when the related datum feature has no geometrical specification (see Figure A.6), or has only geometrical specifications whose tolerance value is not followed by the symbol , or has no geometrical specification complying with Rule G.
Note 3: In these cases, the MMVS for external and internal features of size, lMMVS, is given by Formula (5):
lMMVS=lMMS+0=lMMS (5)
where, lMMS is the maximum material size.
c) Rule G The size of the maximum material virtual condition, MMVC, of the related datum feature shall be the maximum material size, MMS, plus (for external features of size) or minus (for internal features of size) the geometrical tolerance, when the datum feature is controlled by a geometrical specification with the following properties:
1) its tolerance value is followed by the symbol , and
i) it is a form specification and the related datum corresponds to the primary datum of the tolerance indicator where the symbol is indicated next to the datum letter (see Figure A.7), or
ii) is an orientation/location specification whose datum or datum system contains exactly the same datum(s) in the same order as the one(s) called before the related datum in the tolerance indicator where the symbol is indicated next to the datum letter (see Figures A.12 and A.13).
Note 4: In this case, the MMVS for external features of size is as given in Formula (1), and the MMVS for internal features of size is as given in Formula (2). See 3.8, Note 3.
Note 5: When above properties are not observed, Rule F applies.
In the case of Rule G, the datum feature indicator shall be directly connected to that geometrical tolerance indicator from which maximum material virtual condition, MMVC, of the datum feature is controlled (see ISO 5459: 2011, Rule 1, dash 2)
Contents of GB/T 16671-2018
Foreword i
1 Scope
2 Normative references
3 Terms and definitions
4 Maximum material requirement, MMR and least material requirement, LMR
5 Reciprocity requirement, RPR
Annex A (Informative) Examples of tolerancing with , and
Annex B (Informative) Concept diagram
Annex C (Informative) Location in the GPS matrix model
Bibliography
