ISO 20457

• Abstract:

  This document specifies possible manufacturing tolerances for plastic moulded parts. This document specifies all integral features with general tolerances with surface profile tolerance within a specified datum system. It allows for additional specifications in case of functional needs and requirements using the ISO-GPS-tools for dimensional and geometrical tolerating. This document addresses injection moulding, injection compression moulding, transfer moulding, compression moulding and rotational moulding of non-porous moulded parts made from thermoplastics, thermoplastic elastomers and thermosets of thermoplastics. This document is applicable to other plastic processes if agreed to by the contractual parties. Moulded part surface imperfections such as sink marks, undesired flow structures and roughness, as well as joint lines are not addressed in this document. This document is not intended to supplant, replace or in any way interfere with requirements for tolerances found in product standards.

• Status: Not Published
• ICS: 83.140.01 - Rubber and plastics products in general
• Technical Committee: ISO/TC 61/SC 11 - Products
• Drafting Committee: ISO/TC 61/SC 11 - Products
• Current Stage: 6000 - International Standard under publication
• Start Date: 18-Jul-2026
• Completion Date: 18-Jul-2026

• Revises: ISO 20457:2018 - Plastics moulded parts — Tolerances and acceptance conditions
• Effective Date: 14-Sep-2024

Overview

ISO 20457: Plastics moulded parts - Tolerances and acceptance conditions is an international standard developed by the International Organization for Standardization (ISO). It specifies the manufacturing tolerances and acceptance conditions for plastic moulded parts, providing comprehensive guidelines for both designers and manufacturers. The standard covers all integral features with general tolerances and the application of surface profile tolerances within a specified datum system. ISO 20457 is essential for ensuring dimensional accuracy, quality assurance, and consistent communication across the plastics manufacturing industry.

This standard applies to a broad range of manufacturing processes including injection moulding, injection compression moulding, transfer moulding, compression moulding, and rotational moulding. Applicable materials include thermoplastics, thermoplastic elastomers, and thermosets. ISO 20457 sets out general tolerances and acceptance procedures without replacing specific product standards, supporting both contractually agreed requirements and general industry practice.

Key Topics

• General and Direct Tolerancing: Specifies both general default tolerances and direct (individual) tolerances for plastic parts. It supports the use of ISO Geometrical Product Specification (ISO-GPS) tools for dimensional and geometrical tolerancing.
• Limits of Manufacturability: Defines manufacturing limits, taking into account typical process capabilities and material properties such as moulding shrinkage, stiffness, and hardness.
• Acceptance Conditions: Details the requirements for acceptance of moulded plastics parts, including what constitutes an acceptable deviation and how production validation should be conducted.
• Reference Datum and Surface Profile: Emphasizes the importance of a defined datum system for measuring general tolerances and surface profiles.
• Exclusions: Surface imperfections such as sink marks, undesired flow structures, roughness, and joint lines are not covered.
• Adaptability: Can be applied to other plastics processing methods if agreed between parties involved in the contract or specification.
• Documentation: Stresses the necessity of a product definition data set, encompassing detailed dimensional, material, and process specifications.

Applications

ISO 20457 is widely used in the plastics manufacturing industry for:

• Design and Development: Provides designers with guidelines to specify producible and economical tolerances, considering the unique properties of plastics compared to metals.
• Quality Assurance: Assists manufacturers in verifying if produced parts meet the outlined geometrical and dimensional criteria, reducing misunderstandings and costly rework.
• Procurement Contracts: Serves as a contractual reference to define acceptable part tolerances and reduce disputes between customers and suppliers.
• Process Standardization: Encourages efficient communication across global supply chains through harmonized tolerance definitions and acceptance criteria.
• Toolmaking and Validation: Offers guidance for tool designers and mould makers on achievable tolerances, best practices in measurement, and validation of process capability.

Related Standards

ISO 20457 ensures compatibility and synergy with several core ISO standards, such as:

• ISO 294-4: For determining moulding shrinkage in plastics.
• ISO 2577: Specifying shrinkage measurement for thermosetting materials.
• ISO 5459: Concerning the use of datums and datum systems for geometrical tolerancing.
• ISO 8015: Laying out general fundamentals, concepts, and rules for GPS (Geometrical Product Specifications).

Industries adhering to ISO 20457 benefit from improved reliability, reduced scrap rates, and smoother manufacturing workflows in the production of non-porous plastic parts. ISO 20457 is an indispensable resource for anyone seeking best practices and recognized benchmarks in plastics engineering, aiding both OEMs and suppliers in maintaining global quality standards.

FINAL DRAFT
International
Standard
ISO/FDIS 20457
ISO/TC 61/SC 11
Plastics moulded parts —
Secretariat: JISC
Tolerances and acceptance
Voting begins on:
conditions
2026-05-22
Moulages plastiques — Tolérances et conditions de réception
Voting terminates on:
2026-07-17
RECIPIENTS OF THIS DRAFT ARE INVITED TO SUBMIT,
WITH THEIR COMMENTS, NOTIFICATION OF ANY
RELEVANT PATENT RIGHTS OF WHICH THEY ARE AWARE
AND TO PROVIDE SUPPOR TING DOCUMENTATION.
IN ADDITION TO THEIR EVALUATION AS
BEING ACCEPTABLE FOR INDUSTRIAL, TECHNO­
LOGICAL, COMMERCIAL AND USER PURPOSES, DRAFT
INTERNATIONAL STANDARDS MAY ON OCCASION HAVE
TO BE CONSIDERED IN THE LIGHT OF THEIR POTENTIAL
TO BECOME STAN DARDS TO WHICH REFERENCE MAY BE
MADE IN NATIONAL REGULATIONS.
Reference number
ISO/FDIS 20457:2026(en) © ISO 2026

FINAL DRAFT
ISO/FDIS 20457:2026(en)
International
Standard
ISO/FDIS 20457
ISO/TC 61/SC 11
Plastics moulded parts —
Secretariat: JISC
Tolerances and acceptance
Voting begins on:
conditions
Moulages plastiques — Tolérances et conditions de réception
Voting terminates on:
RECIPIENTS OF THIS DRAFT ARE INVITED TO SUBMIT,
WITH THEIR COMMENTS, NOTIFICATION OF ANY
RELEVANT PATENT RIGHTS OF WHICH THEY ARE AWARE
AND TO PROVIDE SUPPOR TING DOCUMENTATION.
© ISO 2026
IN ADDITION TO THEIR EVALUATION AS
All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may
BEING ACCEPTABLE FOR INDUSTRIAL, TECHNO­
LOGICAL, COMMERCIAL AND USER PURPOSES, DRAFT
be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying, or posting on
INTERNATIONAL STANDARDS MAY ON OCCASION HAVE
the internet or an intranet, without prior written permission. Permission can be requested from either ISO at the address below
TO BE CONSIDERED IN THE LIGHT OF THEIR POTENTIAL
or ISO’s member body in the country of the requester.
TO BECOME STAN DARDS TO WHICH REFERENCE MAY BE
MADE IN NATIONAL REGULATIONS.
ISO copyright office
CP 401 • Ch. de Blandonnet 8
CH-1214 Vernier, Geneva
Phone: [phone]
Email: [e-mail]
Website: www.iso.org
Published in Switzerland Reference number
ISO/FDIS 20457:2026(en) © ISO 2026

ii
ISO/FDIS 20457:2026(en)
Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Symbols and abbreviated terms. 2
4.1 General .2
4.2 Symbols .2
4.3 Abbreviated terms .3
5 Tolerancing of plastic moulded parts . 3
5.1 General .3
5.2 Composition of tolerance .6
5.3 Default settings .7
5.4 Direct tolerancing (individual tolerancing) .7
5.5 Draft angles .7
5.6 Dimensioning, tolerancing and measuring of radii .8
5.7 Specification of freeform surfaces .8
6 Description of the technically possible accuracy . 8
6.1 Moulding compound properties .8
6.1.1 General .8
6.1.2 Moulding shrinkage and shrinkage anisotropies .8
6.2 Moulded material stiffness or hardness .9
7 Dimensional and geometrical tolerancing . 10
7.1 Dimensional tolerancing .10
7.1.1 Tolerance grades for features of sizes .10
7.1.2 Determination of the tolerance grades . 13
7.2 Geometrical tolerancing . . .16
7.3 Parting line/Tool offset .19
7.4 Tolerancing of angular dimensions .19
8 General tolerances .20
8.1 General . 20
8.2 Entry of the specification in the technical product documentation . 20
9 Acceptance conditions for moulded part production (ABF) .21
Annex A (informative) Dimensional reference levels for application and production of the
moulded parts .22
Annex B (informative) Causes and influential factors on the moulding shrinkage of non-porous
plastics .24
Annex C (informative) Evaluation of the production expense .25
Annex D (informative) Validation of machine, process and measuring instrumentation
capability .28
Annex E (informative) Main causes for dimension, form and location deviations in moulded
part production .29
Annex F (informative) Example for determining the D dimension for application of Table 9 .30
P
Annex G (informative) Feasible acceptance parameters .32
Bibliography .33

iii
ISO/FDIS 20457:2026(en)
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 committee
has been established has the right to be represented on that committee. International organizations,
governmental and non-governmental, in liaison with ISO, also take part in the work. ISO collaborates closely
with the International Electrotechnical Commission (IEC) on all matters of electrotechnical standardization.
The procedures used to develop this document and those intended for its further maintenance are described
in the ISO/IEC Directives, Part 1. In particular, the different approval criteria needed for the different types
of ISO document should be noted. This document was drafted in accordance with the editorial rules of the
ISO/IEC Directives, Part 2 (see www.iso.org/directives).
ISO draws attention to the possibility that the implementation of this document may involve the use of (a)
patent(s). ISO takes no position concerning the evidence, validity or applicability of any claimed patent
rights in respect thereof. As of the date of publication of this document, ISO had not received notice of (a)
patent(s) which may be required to implement this document. However, implementers are cautioned that
this may not represent the latest information, which may be obtained from the patent database available at
www.iso.org/patents. ISO shall not be held responsible for identifying any or all such patent rights.
Any trade name used in this document is information given for the convenience of users and does not
constitute an endorsement.
For an explanation of the voluntary nature of standards, the meaning of ISO specific terms and expressions
related to conformity assessment, as well as information about ISO's adherence to the World Trade
Organization (WTO) principles in the Technical Barriers to Trade (TBT), see www.iso.org/iso/foreword.html.
This document was prepared by Technical Committee ISO/TC 61, Plastics, Subcommittee SC 11, Products.
This second edition cancels and replaces the first edition (ISO 20457:2018), which has been technically
revised.
The main changes are as follows:
— Clause 1 has been formulated more precisely;
— Term 3.1 on design documentation has been replaced by a new term on product definition data set and
its definition has been reformulated;
— Term 3.2, size, has been changed to "linear size";
— Clause 5 has been reworked including adding of new figures for a better understanding and improved
user-friendliness;
— Clause 6, “Moulding compound properties” has been renamed as “Description of the technically possible
accuracy”;
— Annex F has been reworked, Figure F.1 has been replaced, and a new Figure F.2 has been added.
Any feedback or questions on this document should be directed to the user’s national standards body. A
complete listing of these bodies can be found at www.iso.org/members.html.

iv
ISO/FDIS 20457:2026(en)
Introduction
This document has two intentions. One intention is to give the part designer a guideline for producible
tolerances. The other is to serve as a standard for general tolerances for all geometrical features as well as
for direct tolerances (individual tolerances).
In comparison to metal materials, significantly larger deviations with respect to dimension, form and
location are expected when manufacturing moulded parts. Based on particular properties, such as high
deformability and low stiffness, the functional accuracy requirements in order to economically manufacture
moulded parts are much lower for plastics than for metals.
The physical and chemical properties as well as the material modification options of plastics are vastly
different from those of metals. Properties of plastics relevant to dimensional accuracy in the moulding
application and during processing by the original mould method (injection moulding, compression
moulding, rotational moulding) require a different evaluation and quantification of geometrical tolerances
in comparison to metal materials. The tolerance standards applicable for metal parts, therefore, cannot be
adopted for plastic structures or can only be applied to a very limited extent which led to the development
of this document.
The unique properties of plastics mean that three different dimensional reference levels defined in Annex A
and characterized in respect to the main influential factors are taken into consideration.
The following is the preferred sequence of steps to ensure effective cooperation in the effective design and
development of moulded parts.
a) The part designer specifies the functionally required tolerances based on the application requirements
including, part functionality, use environment, and any assembly requirements.
b) The moulded part manufacturer confirms that the functionally required tolerance is greater than or
equal to the tolerance capability of the manufacturing technology to be used. This is to avoid impractical
tolerances which cannot be achieved without incurring adverse economic or productivity effects. The
functionally required tolerances is always defined in the product definition data set.
c) The functionally required tolerances shall always be defined in the product definition data set in order
to establish the basis for determining the moulding shrinkage. This is to prevent situations in which the
functionally required tolerances cannot be achieved, if at all, without excessive scrap generation and
excessive costs. After order placement, calculated values with respect to the moulding shrinkage shall
be agreed between the part manufacturer and toolmaker or tool designer, with consultation with the
material supplier as necessary.
Dimensional control of the moulded part is primarily affected by the material specified, the part design and
tool layout, and the processing conditions.
In addition to the factors affecting dimensional control, there are other factors which influence dimensions,
part integrity and mechanical properties. These factors include anisotropic behaviour, warpage and
distortion due to non-uniform thicknesses and resulting non-uniform cooling rates, and fill profiles.
These factors and the basic complexity of polymer systems make standardization much more difficult in
comparison to conventional materials such as metals.
Because of the unavoidable process-induced factors, deviations are therefore expected in the moulded part.
The procedure in case of deviations depends on the function of the moulded part and is subject to mandatory
contractual agreement.
— eliminate deviation by design measures (strengthening ribs, optimized material thickness, optimized fill
profiles, etc.);
— correct deviation by specified retention in the tool, i.e. extended cooling cycles;
— acceptance of non-conformance.

v
ISO/FDIS 20457:2026(en)
NOTE 1 Process-induced deviations can be reduced both by effective design of the moulded part and by optimization
of the production process.
NOTE 2 The conventional tolerance chain calculation presupposes rigid bodies and is therefore primarily
unsuitable for plastic parts.
vi
FINAL DRAFT International Standard ISO/FDIS 20457:2026(en)
Plastics moulded parts — Tolerances and acceptance
conditions
1 Scope
This document specifies geometrical and dimensional tolerances for plastic moulded parts including:
— limits of technical manufacturability according to the manufacturing effort for direct tolerances;
— general tolerances of plastic moulded parts;
— acceptance conditions of plastic moulded parts;
— modification of the drawing default according to ISO 8015, in accordance to the environmental conditions
common in the plastics industry.
This document is applicable to non-porous moulded parts made from thermoplastics, thermoplastic
elastomers and thermosets of thermoplastics, made by injection moulding, injection compression moulding,
transfer moulding, compression moulding and rotational moulding. This document is applicable to other
plastic processes, if agreed to by the contractual parties.
Moulded part surface imperfections such as sink marks, undesired flow structures and roughness, as well
as joint lines are not addressed in this document.
2 Normative references
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 294-4, Plastics — Injection moulding of test specimens of thermoplastic materials — Part 4: Determination
of moulding shrinkage
ISO 2577, Plastics — Thermosetting moulding materials — Determination of shrinkage
ISO 5459, Geometrical product specifications (GPS) — Geometrical tolerancing — Datums and datum systems
ISO 8015, Geometrical product specifications (GPS) — Fundamentals — Concepts, principles and rules
3 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO 8015 and the following apply.
ISO and IEC maintain terminology databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https:// www .iso .org/ obp
— IEC Electropedia: available at https:// www .electropedia .org/

ISO/FDIS 20457:2026(en)
3.1
product definition data set
collection of one or more computer file(s) that discloses (directly or by reference), by means of graphic or
textual presentations, or combinations of both, the physical and functional requirements of a product
Note 1 to entry: These are initially 3D data records and drawings as well as part lists. They might be supplemented by
measuring and test specifications. 3D data records or drawings alone only fully describe plastic moulded parts in rare
exceptional cases.
Note 2 to entry: The aim of a specification is to describe the function completely with GPS characteristics (ISO 8015).
This is done by means of references, direct tolerancing and general tolerances.
[SOURCE: ISO 10209:2022, 3.1.70, modified — Notes 1 to entry have been added]
3.2
linear size
dimensional parameter considered variable for a feature of size that can be defined on a nominal feature or
on an associated feature
Note 1 to entry: A linear size is e.g. the diameter of a cylinder or the distance between two parallel opposite planes,
two opposing lines, and two concentric circles. Depending on the type of linear feature of size, the terms “diameter”,
“width”, and “thickness” are synonyms for size. Distances in the sense of step dimensions are not size dimensions
[SOURCE: ISO 14405-1:2025, 3.2, modified — Term changed from “size” to “linear size”, in Note 1 to entry
the introductory phrase changed]
3.3
general tolerance
tolerance on geometrical elements used as default, if the element has no direct tolerance (individual
tolerance)
4 Symbols and abbreviated terms
4.1 General
The symbols and abbreviated terms according to the ISO 1043 series, ISO 18064 and the following symbols
and abbreviated terms apply for the application of this document.
4.2 Symbols
C tolerance mean dimension
C tolerance mean dimension for moulded part application
A
C tolerance mean dimension for moulded part production
F
C tolerance mean dimension for tool contour production
W
D furthest distance in the space between the element to be toleranced and the origin of the datum
P
system used for this positional tolerancing
L moulded part dimension
F
L tool contour dimension
W
N nominal dimension for moulded part drawings
F
NW non-tool-specific dimensions
P total number of points
g
ISO/FDIS 20457:2026(en)
P point evaluation of the individual influences
i
T tolerance
t form and location tolerance
T moulded part application tolerance
A
T moulded part production tolerance
F
T tool contour production tolerance
W
S moulding shrinkage
M
moulding shrinkage transverse to the melt flow direction
S
M⊥
moulding shrinkage parallel to the melt flow direction
S
MII
maximum moulding shrinkage
S
Mmax
minimum moulding shrinkage
S
Mmin
average calculated value for the moulding shrinkage
S
MR
W tool-specific dimensions
∆L dimensional shift
∆L application-induced dimensional shift
A
∆L moulding-induced dimensional shift
V
∆S distribution of the moulding shrinkage
∆S
difference between VS and VS
M
II
⊥
4.3 Abbreviated terms
ABF acceptance conditions for moulded part production
ABW acceptance conditions for tool production
GA maximum permissible deviation
IRHD International Rubber Hardness Degree
ISIR Initial Sample Inspection Report
IT standard tolerance
TG tolerance grade
5 Tolerancing of plastic moulded parts
5.1 General
Relevant functions of the part shall be toleranced directly in order to enable the part manufacturer to
optimize his manufacturing process accordingly. Secondary functions can be toleranced by means of the
general tolerance.
ISO/FDIS 20457:2026(en)
Due to the special properties of plastic moulded parts, the following entries shall be made, where appropriate,
in or on the title block in the product definition data set (drawing) in addition to the direct tolerancing, the
specification of the general tolerance class and the reference system for general tolerances:
— for non-rigid parts: ISO 10579 - NR, including additional restrained condition;
— if envelope principle is desired for linear size: Linear size ISO 14405 .
Moulded part drawings or CAD data records correspond to the nominal geometry. The tolerances are
symmetrical to the nominal geometry.
The procedure for the verification of tolerances shall be unambiguously defined and shall be a part of the
contract. It is recommended to separate between Initial Sample Inspection Report (ISIR) and running
production report (requalification). This may include or exclude the individual tolerances and general
tolerances or specified functional tests (e.g. tightness, dielectric strength). If nothing has been stated in the
contract, only individually indicated tolerances are subject for verification. The verification obligation of all
toleranced surfaces for the initial sample approval refers to the measurement within the scope of the initial
sample approval. This is to be stored as documented information.
Certain moulded parts, when removed from their manufacturing environment, can deform significantly
from their defined limits owing to their weight, flexibility or the release of internal stresses resulting from
the manufacturing processes.
Functionally reasonable references with adequate form stiffness shall be specified.
In the case of non-rigid parts, the measuring concept is of special importance (functional orientation, datum
system and overdetermination, gravitational influence, pretension, etc.). See also ISO 10579.
For the orientation of the part, datum target points or small datum target areas shall be used instead of
datum features (e.g. complete planes).
Due to accuracy, integral references shall be created from reference points or as common references from
small geometry elements.
Figure 1 a) shows a reference system of reference elements. This is not optimal for moulded parts due to the
draft angles, since the references are perpendicular to each other and thus only the edge is used for slanted
secondary or tertiary references. In Figure 1 b), the reference system is formed from reference points. Since
the moulded part is only aligned at points, the draft angles do not play a role. The design in Figure 1 c)
also takes into account potential distortion of the surface at the primary reference (A-A) and reduces the
reference to three small raised surfaces.

ISO/FDIS 20457:2026(en)
a) Inadequat reference system from reference elements
b) Reference system from reference points

ISO/FDIS 20457:2026(en)
c) Reference system from reference points suitable for plastics
Key
1 datum A
2 datum B
3 datum A
4 datum B
5 common datum A – A
6 datum B
Figure 1 — Datum systems
It is important that the datum system is stable.
NOTE 1 The datum system reflects the orientation of the part in the assembly.
NOTE 2 Reference elements or reference points on mould partition lines, ejector surfaces and inserts are critical
regarding the reproducibility of the reference system.
In the case of parts moulded from dissimilar materials (e.g. over-moulding) or assemblies using multiple
component parts moulded from different materials, a separate tolerance grade shall be specified for each
material used. In the case of cross-material size dimensions, the more inaccurate material is the basis for
determining the tolerance.
5.2 Composition of tolerance
Figure 2 gives an overview about the intentions and about the composition of tolerance.

ISO/FDIS 20457:2026(en)
NOTE Accurate production see Table C.1.
Figure 2 — Determination of tolerances for plastic moulded parts
Tolerances of features with functional requirements shall be directly specified. General tolerances apply to
non-functional features (e.g. surface profiles, line profiles) and can be as large as practically possible.
5.3 Default settings
Including ISO 20457 in the title block changes the following drawing defaults:
— it automatically causes calling up of: Tolerance ISO 8015 : reference temperature 23 °C ± 2 K and a
relative humidity of 50 % ± 10 % according to ISO 291;
5.4 Direct tolerancing (individual tolerancing)
Functional relevant tolerances (dimensional or geometrical) shall be explicitly (individual) specified.
Simple and accurate production can also be required for directly toleranced characteristics (linear sizes or
geometrical tolerances) without coordination.
The dimensional tolerance shall be indicated directly by dimensions for moulded parts with justifiably high
dimensional stability requirements. When doing so, it shall be noted that the dimensional boundary lines
or points represent inspection dimensions (reference dimensions, acceptance dimensions). The number of
directly toleranced functional elements/dimensions per moulded part shall be kept as low as possible for
economic reasons.
When tolerancing dimensions, it should be noted according to ISO 14405 that only linear sizes (diameter of
cylinder/circle, distance between two opposite planes/lines) can be specified with ± tolerances, otherwise
position tolerances or surface profiles shall be used.
Verification shall be defined separately in measurement specifications in accordance with the duality
principle of ISO 8015, which shall be part of the contract between the manufacturer and customer.
For functionally relevant measurement specifications, measurement points shall be defined on the
measurement surfaces to enable comparable measurement results.
NOTE The direct tolerances determine the required production expense.
5.5 Draft angles
Drafts (also draft angles) are production-induced inclinations on the moulded part in the demoulding
orientation of moving tool parts (e.g. punches, gate valves, jaws), which are specified as an integral

ISO/FDIS 20457:2026(en)
component of the moulded part drawings or the CAD data records of the moulded part manufacturer for tool
design and tool making as well as parts production.
Inclination dimension differences specified in terms of design are not a component of the nominal model and
not a component of dimensional tolerances or form and location deviations.
Measuring points shall be defined at suitable areas for functional dimensions in the specification in order to
allow for comparable measuring results.
If the geometrical deviation due to the draft angle is less than 5 % of the tolerance, the dimension can still be
treated as a linear size.
5.6 Dimensioning, tolerancing and measuring of radii
Minimum 90° of the circle segment shall be provided as a measurable contour for the specification of radii.
NOTE Radii can alternatively be toleranced by profile forms.
5.7 Specification of freeform surfaces
Functional free form surfaces shall be specified with surface profile tolerances.
6 Description of the technically possible accuracy
6.1 Moulding compound properties
6.1.1 General
In order to classify the materials with regard to their accuracy-relevant properties, which influence the
achievable accuracy, they are classified in a general assignment scheme for the various moulding compounds.
6.1.2 Moulding shrinkage and shrinkage anisotropies
The moulding shrinkage (VS) is the relative difference between the tool contour dimension (L ) at
W
23 °C ± 2 K and the corresponding moulded part dimensions L 16 h to 24 h after production, stored until
F
measurement and measured according to ISO 291:2008, Table 1, unless otherwise specified by contract or
the relevant standard. It is calculated according to Formula (1).
 L 
F
S 1 100% (1)
 
M
 
L
 
W
where
L is the moulded part dimension;
F
L is the tool contour dimension.
W
The relative moulding shrinkage for thermoplastics and thermoplastic elastomers shall be determined (e.g.
test panels) according to ISO 294-4 and for thermosets according to ISO 2577 on standard test specimens.
Physical causes of the moulding shrinkage and the effect of influencing factors are indicated in Annex B and
Annex E.
Shrinkage anisotropy is quantified by the absolute difference ∆VS from moulding shrinkage transverse to
the melt flow direction VS and the moulding shrinkage parallel to the melt flow direction VS . See
II
⊥
Formula (2).
ISO/FDIS 20457:2026(en)
SS S (2)
MM MII
Primary causes for anisotropicity include:
— moulding impediments as a result of different thermal contraction by solidified boundary layers, material
concentrations and locally different tool contour temperatures as well as by the effect of the moulded
part design;
— shrinkage differences due to over-moulded parts for example metal inserts;
— orientation of fillers and reinforcements, and molecular orientation as a result of shear and elongation
flows. In particular, particle shape and aspect ratio (length-thickness ratio or side-thickness ratio) of the
fillers and reinforcements affect the anisotropy characteristics.
It can be derived from the variety of influences on the moulding shrinkage and shrinkage anisotropy that
numerical values are only realistic as range data. The resultant distribution of the moulding shrinkage ∆S is
derived from the extreme values VS and VS It is calculated according to Formula (3).
max min
SS S (3)
Mmax Mmin
The degree and uniformity of the shrinkage distribution can be affected by many factors including
production conditions (process optimization), batch-relevant moulding compound differences, moulded
part shape and sprue technology.
Average calculated values of the moulding shrinkage VS are specifications for tool design, construction and
R
sampling of the tools. It is calculated according to Formula (4).
SS05, S (4)

MR Mmax Mmin
This calculated value, which is a basis for the tool design, is primarily expected from the moulded part
manufacturer, as the latter can actively influence the shrinkage in limits and usually has corresponding
data. They can be generated as a by-product from dimensional check measurements. In special cases, the
shrinkage values are to be made more precise by sampling with similar tools. In addition, the moulded part
manufacturer can use corresponding data and experience of the moulding compound manufacturer. In the
case of distinct shrinkage anisotropy, the shrinkage differences can be considered to a limited extent by
dimensional provisions in the tool. Computer-assisted shrinkage and deformation statements might be able
to provide information in respect to this.
The shrinkage distribution is also of major significance for the attainable production accuracy. This value
range is to be estimated according to experience of the moulded part manufacturer.
If the shrinkage anisotropy cannot be considered adequately in the contour calculation, a larger shrinkage
distribution and, hence, deformation is to be expected. A timely coordination between the customer and
moulded part manufacturer is necessary in respect to this.
6.2 Moulded material stiffness or hardness
NOTE The main cause for this is the different stiffness or hardness of the moulding material directly after removal
from the mould. It is related to the original modulus of elasticity from the short-term test according to ISO 527-1 as well
as by the Shore indentation hardness according to ISO 868:2003, method A and method D or by the ball indentation
hardness for elastomers according to ISO 48-2. All tests refer to 23 °C and normally conditioned test specimens.
The elastic recovery (relaxation) of the moulding material after removal of the part has a significant effect on
the form and location tolerance and the linear sizes. The required data shall be provided in the specifications
of the raw material suppliers.

ISO/FDIS 20457:2026(en)
7 Dimensional and geometrical tolerancing
7.1 Dimensional tolerancing
7.1.1 Tolerance grades for features of sizes
To align moulding-related production tolerances for plastic parts with ISO 286-1 and ISO 286-2, adjustments
were made. Nine tolerance grades (TG1 to TG9) in three nominal dimension ranges were mapped to ISO
basic tolerance grades (IT) for tool-specific dimensions (see Table 1).
Table 1 — Tolerance grades (TG) with associated ISO standard tolerance grades (IT) according to
ISO 286-1
Nominal dimension ISO standard tolerance grades (IT) for tool-specific dimensions
mm TG1 TG2 TG3 TG4 TG5 TG6 TG7 TG8 TG9
1 to 6 8 9 10 11 12 13 14 15 16
>6 to 120 9 10 11 12 13 14 15 16 17
>120 to 1 000 — 11 12 13 14 15 16 17 18
The tolerances are subject to mandatory agreement as a rule for nominal dimensions below 1 mm and above 1 000 mm.
NOTE 1 Table 1 serves as information for the basic layout and content of Table 2. Further usage is not required.
NOTE 2 Features of sizes cover inner and outer cylinders (hole/shafts), inner and outer parallel, opposite planes
(slot/keys) (see ISO 17450-1).
The permissible tolerances for plastic moulded parts are summarized for the practical application in Table 2.
The manufacturing method rotational moulding is classified into tolerance grade 9.
Different deformations and deviations of location of tool parts caused during the pressure load taken
into account by the differentiation of tool-specific and non-tool-specific moulded part dimensions, as the
different types of tool contour fixations result in different degrees of accuracy. Tool-specific dimensions
are dimensions in the same tool part, while non-tool-specific dimensions are derived from the interaction
of different tool parts and which hence tend to cause larger dimensional distributions (see Figure 3 and
Figure 4).
Key
1 closing direction
2 movement direction of the slide
x linear size or theoretically exact dimension (TED)
NOTE Linear size only for cylinders, spheres and two parallel opposite planes (according to ISO 14405-1).
Figure 3 — Tool-specific dimensions

ISO/FDIS 20457:2026(en)
Key
1 closing direction
2 movement direction of the slide
x linear size or theoretically exact dimension (TED)
NOTE Linear size only for cylinders, spheres and two parallel opposite planes (according to ISO 14405-1).
Figure 4 — Non-tool-specific dimensions

ISO/FDIS 20457:2026(en)
Table 2 — Plastic moulded part tolerances as symmetrical tolerances for features of linear sizes
Dimensions in mllimetres
Tolerances (GA) for nominal size ranges
Tolerance
1 to >3 to >6 to >10 to >18 to >30 to >50 to >80 to >120 to >180 to >250 to >315 to >400 to >500 to >630 to >800 to
grade
3 6 10 18 30 50 80 120 180 250 315 400 500 630 800 1 000
W ±0,007 ±0,012 ±0,018 ±0,022 ±0,026 ±0,031 ±0,037 ±0,044 — — — — — — — —
TG1
NW ±0,012 ±0,018 ±0,022 ±0,026 ±0,031 ±0,037 ±0,044 ±0,055 — — — — — — — —
W ±0,013 ±0,019 ±0,029 ±0,035 ±0,042 ±0,050 ±0,060 ±0,090 ±0,13 ±0,15 ±0,16 ±0,18 ±0,20 — — —
TG2
NW ±0,019 ±0,029 ±0,035 ±0,042 ±0,050 ±0,060 ±0,090 ±0,13 ±0,15 ±0,16 ±0,18 ±0,20 ±0,22 — — —
W ±0,020 ±0,030 ±0,05 ±0,06 ±0,07 ±0,08 ±0,10 ±0,15 ±0,20 ±0,23 ±0,26 ±0,29 ±0,32 ±0,35 ±0,40 ±0,45
TG3
NW ±0,030 ±0,050 ±0,06 ±0,07 ±0,08 ±0,10 ±0,15 ±0,20 ±0,23 ±0,26 ±0,29 ±0,32 ±0,35 ±0,40 ±0,45 ±0,53
W ±0,03 ±0,05 ±0,08 ±0,09 ±0,11 ±0,13 ±0,15 ±0,23 ±0,32 ±0,35 ±0,41 ±0,45 ±0,49 ±0,55 ±0,63 ±0,70
TG4
NW ±0,05 ±0,08 ±0,09 ±0,11 ±0,13 ±0,15 ±0,23 ±0,32 ±0,35 ±0,41 ±0,45 ±0,49 ±0,55 ±0,63 ±0,70 ±0,83
W ±0,05 ±0,08 ±0,11 ±0,14 ±0,17 ±0,20 ±0,23 ±0,36 ±0,50 ±0,58 ±0,65 ±0,70 ±0,78 ±0,88 ±1,00 ±1,15
TG5
NW ±0,08 ±0,11 ±0,14 ±0,17 ±0,20 ±0,23 ±0,36 ±0,50 ±0,58 ±0,65 ±0,70 ±0,78 ±0,88 ±1,00 ±1,15 ±1,30
W ±0,07 ±0,12 ±0,18 ±0,22 ±0,26 ±0,31 ±0,37 ±0,57 ±0,80 ±0,93 ±1,05 ±1,15 ±1,25 ±1,40 ±1,60 ±1,80
TG6
NW ±0,12 ±0,18 ±0,22 ±0,26 ±0,31 ±0,37 ±0,57 ±0,80 ±0,93 ±1,05 ±1,15 ±1,25 ±1,40 ±1,60 ±1,80 ±2,10
W ±0,13 ±0,20 ±0,29 ±0,35 ±0,42 ±0,50 ±0,60 ±0,90 ±1,25 ±1,45 ±1,60 ±1,80 ±2,00 ±2,20 ±2,50 ±2,80
TG7
NW ±0,20 ±0,29 ±0,35 ±0,42 ±0,50 ±0,60 ±0,90 ±1,25 ±1,45 ±1,60 ±1,80 ±2,00 ±2,20 ±2,50 ±2,80 ±3,30
W ±0,20 ±0,30 ±0,45 ±0,55 ±0,65 ±0,80 ±0,95 ±1,40 ±2,00 ±2,30 ±2,60 ±2,85 ±3,15 ±3,50 ±4,00 ±4,50
TG8
NW ±0,30 ±0,45 ±0,55 ±0,65 ±0,80 ±0,95 ±1,40 ±2,00 ±2,30 ±2,60 ±2,85 ±3,15 ±3,50 ±4,00 ±4,50 ±5,30
TG9 ±0,48 ±0,75 ±0,90 ±1,05 ±1,25 ±1,50 ±2,25 ±3,15 ±3,60 ±4,05 ±4,45 ±4,90 ±5,40 ±6,20 ±7,10 ±8,50
NOTE 1 W: Tool-specific dimensions; NW: Non-tool-specific dimensions.
NOTE 2 The differentiation of tool-specific and non-tool-specific dimension is not necessary for TG9.
NOTE 3 Tolerance mean dimensions apply as nominal sizes for moulded part drawings (N = C ). For tolerancing of the distance between parallel surfaces that do not face each other directly but are arranged shifted to one another,
F F
the D dimension according to 7.2 of this document is used as nominal size.
P
NOTE 4 Dimensions under 1 mm and above 1 000 mm are subject to mandatory agreement.
NOTE 5 Only the limit values for non-tool-specific dimensions are used for general tolerances.
NOTE 6 Tolerances for material thicknesses are subject to mandatory agreement.
NOTE 7 General tolerances are indicated in the product definition data set, for example: ISO 20457:2026 – TG6.
NOTE 8 For validation of machine and process capability, see Annex D.

ISO/FDIS 20457:2026(en)
7.1.2 Determination of the tolerance grades
7.1.2.1 General
The required degree of accuracy of the moulded part production is defined with the corresponding tolerance
grade according to Table 3. An oriented assignment scheme using point evaluation of five individual
influences P with the total number of points P yields the tolerance grade according to Table 3 (exception is
i g
the rotational moulding which always equals TG9):
PP PP PP (5)
g 12 34 5
where
P is the total number of points;
g
P is the point evaluation of the individual influences.
i
Table 3 — Point assignment of the tolerance grades
TG TG1 TG2 TG3 TG4 TG5 TG6 TG7 TG8 TG9
P 1 2 3 4 5 6 7 8 ≥9
g
In the process of determining, P , [as shown in Formula (5)] inputs from the moulded part manufacturer
g
might be necessary.
Figure 5 shows an overview of the process to determine the tolerance grade.

ISO/FDIS 20457:2026(en)
a
Simple production = Production realized with general tolerances. Dimensional stability requirements that do
not form any special quality focus (see Table 8, Series 1).
b
Exemplary selection criteria are listed in Annex C to assist the series assignment.
Figure 5 — Procedure to determine the tolerance grade TG
7.1.2.2 Evaluation of the production process and moulding compound properties (P to P )
1 4
The point assignment is conducted with the following evaluation matrices (see Table 4, Table 5, Table 6 and
Table 7), whereby the evaluation is at the user’s discretion for limit ranges of the properties (P to P ).
2 4
Table 4 — Evaluation matrices 1
Production process P
Injection moulding, injection compression moulding, transfer moulding 1
Compression moulding, impact extrusion 2
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ISO/DIS FDIS 20457:2025(E2026(en)
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ISO/FDIS 20457:2026(en)
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Contents Page
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Foreword . vi
Introduction . viii
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Symbols and abbreviated terms . 2
4.1 General . 2
4.2 Symbols . 2
4.3 Abbreviated terms . 3
5 Tolerancing of plastic moulded parts . 4
5.1 General . 4
5.2 Composition of tolerance . 8
5.3 Default settings . 8
5.4 Direct tolerancing (individual tolerancing) . 9
5.5 Draft angles . 9
5.6 Dimensioning, tolerancing and measuring of radii . 9
5.7 Specification of freeform surfaces . 9
6 Description of the technically possible accuracy . 10
6.1 Moulding compound properties . 10
6.2 Moulded material stiffness or hardness . 11
7 Dimensional and geometrical tolerancing . 11
7.1 Dimensional tolerancing . 11
7.2 Geometrical tolerancing . 21
7.3 Parting line/Tool offset . 24
7.4 Tolerancing of angular dimensions . 25
8 General tolerances. 25
8.1 General . 25
8.2 Entry of the specification in the technical product documentation . 25
9 Acceptance conditions for moulded part production (ABF) . 27
Annex A (informative) Dimensional reference levels for application and production of the
moulded parts . 28
Annex B (informative) Causes and influential factors on the moulding shrinkage of non-porous
plastics . 31
Annex C (informative) Evaluation of the production expense. 32
Annex D (informative) Validation of machine, process and measuring instrumentation
capability . 35
Annex E (informative) Main causes for dimension, form and location deviations in moulded
part production . 36
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Annex F (informative) Example for determining the D dimension for application of Table 9 . 37
P
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Annex G (informative) Feasible acceptance parameters . 41
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Bibliography . 42
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Foreword . v
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iii
ISO/DIS FDIS 20457:2025(E2026(en)
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Introduction . vii
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1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Symbols and abbreviated terms . 2
4.1 General . 2
4.2 Symbols . 2
4.3 Abbreviated terms . 3
5 Tolerancing of plastic moulded parts . 3
5.1 General . 3
5.2 Composition of tolerance . 6
5.3 Default settings . 7
5.4 Direct tolerancing (individual tolerancing) . 7
5.5 Draft angles . 8
5.6 Dimensioning, tolerancing and measuring of radii . 8
5.7 Specification of freeform surfaces . 8
6 Description of the technically possible accuracy . 8
6.1 Moulding compound properties . 8
6.1.1 General . 8
6.1.2 Moulding shrinkage and shrinkage anisotropies . 8
6.2 Moulded material stiffness or hardness . 9
7 Dimensional and geometrical tolerancing . 10
7.1 Dimensional tolerancing . 10
7.1.1 Tolerance grades for features of sizes . 10
7.1.2 Determination of the tolerance grades . 14
7.2 Geometrical tolerancing . 18
7.3 Parting line/Tool offset . 21
7.4 Tolerancing of angular dimensions . 22
8 General tolerances. 22
8.1 General . 22
8.2 Entry of the specification in the technical product documentation . 22
9 Acceptance conditions for moulded part production (ABF) . 24
Annex A (informative) Dimensional reference levels for application and production of the
moulded parts . 25
A.1 Sizes and dimensional relations . 25
A.2 Application conditions . 25
A.3 Moulding-induced dimensional shift, ∆LV . 26
Annex B (informative) Causes and influential factors on the moulding shrinkage of non-porous
plastics . 27
Annex C (informative) Evaluation of the production expense. 28
Annex D (informative) Validation of machine, process and measuring instrumentation
capability . 31
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ISO/FDIS 20457:2026(en)
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Annex E (informative) Main causes for dimension, form and location deviations in moulded
part production . 32
Annex F (informative) Example for determining the DP dimension for application of Table 9 . 33
F.1 General . 33
F.2 Relation between Table 2 and Table 9 . 34
Annex G (informative) Feasible acceptance parameters . 35
Bibliography . 36

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ISO/DIS FDIS 20457:2025(E2026(en)
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Foreword
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ISO (the International Organization for Standardization) is a worldwide federation of national standards
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bodies (ISO member bodies). The work of preparing International Standards is normally carried out through
and numbers, Tab stops: Not at 0.71 cm
ISO technical committees. Each member body interested in a subject for which a technical committee has been
established has the right to be represented on that committee. International organizations, governmental and
non-governmental, in liaison with ISO, also take part in the work. ISO collaborates closely with the
International Electrotechnical Commission (IEC) on all matters of electrotechnical standardization.
The procedures used to develop this document and those intended for its further maintenance are described
in the ISO/IEC Directives, Part 1. In particular, the different approval criteria needed for the different types of
ISO document should be noted. This document was drafted in accordance with the editorial rules of the
ISO/IEC Directives, Part 2 (see www.iso.org/directives).
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ISO draws attention to the possibility that the implementation of this document may involve the use of (a)
patent(s). ISO takes no position concerning the evidence, validity or applicability of any claimed patent rights
in respect thereof. As of the date of publication of this document, ISO had not received notice of (a) patent(s)
which may be required to implement this document. However, implementers are cautioned that this may not
represent the latest information, which may be obtained from the patent database available at
www.iso.org/patents.www.iso.org/patents. ISO shall not be held responsible for identifying any or all such
patent rights.
Any trade name used in this document is information given for the convenience of users and does not
constitute an endorsement.
For an explanation of the voluntary nature of standards, the meaning of ISO specific terms and expressions
related to conformity assessment, as well as information about ISO's adherence to the World Trade
Organization (WTO) principles in the Technical Barriers to Trade (TBT), see
www.iso.org/iso/foreword.htmlwww.iso.org/iso/foreword.html.
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This document was prepared by Technical Committee ISO/TC 61, Plastics, Subcommittee SC 11, Products.
This second edition cancels and replaces the first edition (ISO 20457:2018), which has been technically Formatted: Default Paragraph Font
revised.
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The main changes are as follows:
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— — Clause 1Clause 1 has been formulated more precisely;
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— — Term 3.13.1 on design documentation has been replaced by a new term on product definition data set
Not at 0.7 cm + 1.4 cm + 2.1 cm + 2.8 cm + 3.5 cm + 4.2
and its definition has been reformulated;
cm + 4.9 cm + 5.6 cm + 6.3 cm + 7 cm
— — Term 3.2 on3.2, size, has been changed to "linear size;";
— — Clause 5Clause 5 has been reworked including adding of new figures for a better understanding and
improved user-friendliness;
— — Clause 6,Clause 6, “Moulding compound properties” has been renamed as “Description of the
technically possible accuracy”;
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ISO/FDIS 20457:2026(en)
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— — Annex FAnnex F has been reworked, Figure F.1Figure F.1 has been replaced, and a new
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Any feedback or questions on this document should be directed to the user’s national standards body. A Formatted: English (United Kingdom)
complete listing of these bodies can be found at www.iso.org/members.htmlwww.iso.org/members.html.
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vii
ISO/DIS FDIS 20457:2025(E2026(en)
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Introduction
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This document has two intentions. One intention is to give the part designer a guideline for producible Adjust space between Asian text and numbers
tolerances. The other is to serve as a standard for general tolerances for all geometrical features as well as for
direct tolerances (individual tolerances).
In comparison to metal materials, significantly larger deviations with respect to dimension, form and location
are expected when manufacturing moulded parts. Based on particular properties, such as high deformability
and low stiffness, the functional accuracy requirements in order to economically manufacture moulded parts
are much lower for plastics than for metals.
The physical and chemical properties as well as the material modification options of plastics are vastly
different from those of metals. Properties of plastics relevant to dimensional accuracy in the moulding
application and during processing by the original mould method (injection moulding, compression moulding,
rotational moulding) require a different evaluation and quantification of geometrical tolerances in comparison
to metal materials. The tolerance standards applicable for metal parts, therefore, cannot be adopted for plastic
structures or can only be applied to a very limited extent which led to the development of this document.
The unique properties of plastics mean that three different dimensional reference levels defined in
Annex AAnnex A and characterized in respect to the main influential factors are taken into consideration.
The following is the preferred sequence of steps to ensure effective cooperation in the effective design and
development of moulded parts.
a) a) The part designer specifies the functionally required tolerances based on the application Formatted: Numbered + Level: 1 + Numbering Style: a, b,
c, … + Start at: 1 + Alignment: Left + Aligned at: 0 cm +
requirements including, part functionality, use environment, and any assembly requirements.
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text, Adjust space between Asian text and numbers, Tab
b) b) The moulded part manufacturer confirms that the functionally required tolerance is greater
stops: Not at 0.7 cm + 1.4 cm + 2.1 cm + 2.8 cm + 3.5 cm
than or equal to the tolerance capability of the manufacturing technology to be used. This is to avoid
+ 4.2 cm + 4.9 cm + 5.6 cm + 6.3 cm + 7 cm
impractical tolerances which cannot be achieved without incurring adverse economic or productivity
effects. The functionally required tolerances is always defined in the product definition data set.
c) c) The functionally required tolerances shall always be defined in the product definition data set
in order to establish the basis for determining the moulding shrinkage. This is to prevent situations in
which the functionally required tolerances cannot be achieved, if at all, without excessive scrap generation
and excessive costs. After order placement, calculated values with respect to the moulding shrinkage shall
be agreed between the part manufacturer and toolmaker or tool designer, with consultation with the
material supplier as necessary.
Dimensional control of the moulded part is primarily affected by the material specified, the part design and
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tool layout, and the processing conditions.
In addition to the factors affecting dimensional control, there are other factors which influence dimensions,
part integrity and mechanical properties. These factors include anisotropic behaviour, warpage and distortion
due to non-uniform thicknesses and resulting non-uniform cooling rates, and fill profiles. These factors and
the basic complexity of polymer systems make standardization much more difficult in comparison to
conventional materials such as metals.
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ISO/FDIS 20457:2026(en)
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Because of the unavoidable process-induced factors, deviations are therefore expected in the moulded part.
The procedure in case of deviations depends on the function of the moulded part and is subject to mandatory
contractual agreement.
— — eliminate deviation by design measures (strengthening ribs, optimized material thickness, optimized
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fill profiles, etc.);
Not at 0.7 cm + 1.4 cm + 2.1 cm + 2.8 cm + 3.5 cm + 4.2
cm + 4.9 cm + 5.6 cm + 6.3 cm + 7 cm
— — correct deviation by specified retention in the tool, i.e. extended cooling cycles;
— — acceptance of non-conformance.
NOTE 1 Process-induced deviations can be reduced both by effective design of the moulded part and by optimization
of the production process.
NOTE 2 The conventional tolerance chain calculation presupposes rigid bodies and is therefore primarily unsuitable
for plastic parts.
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DRAFT International Standard ISO/FDIS 20457:2026(en)

Plastics moulded parts — Tolerances and acceptance conditions
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1 Scope
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This document specifies geometrical and dimensional tolerances for plastic moulded parts including:
— — limits of technical manufacturability according to the manufacturing effort for direct tolerances;
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— — general tolerances of plastic moulded parts;
cm + 4.9 cm + 5.6 cm + 6.3 cm + 7 cm
— — acceptance conditions of plastic moulded parts;
— — modification of the drawing default according to ISO 8015, in accordance to the environmental Formatted: Default Paragraph Font
conditions common in the plastics industry.
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This document is applicable to non-porous moulded parts made from thermoplastics, thermoplastic Formatted: Adjust space between Latin and Asian text,
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elastomers and thermosets of thermoplastics, made by injection moulding, injection compression moulding,
transfer moulding, compression moulding and rotational moulding. This document is applicable to other
plastic processes, if agreed to by the contractual parties.
Moulded part surface imperfections such as sink marks, undesired flow structures and roughness, as well as
joint lines are not addressed in this document.
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2 Normative references Formatted: Default Paragraph Font
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The following documents are referred to in the text in such a way that some or all of their content constitutes
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requirements of this document. For dated references, only the edition cited applies. For undated references,
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the latest edition of the referenced document (including any amendments) applies.
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Not at 0.7 cm + 1.4 cm + 2.1 cm + 2.8 cm + 3.5 cm + 4.2
ISO 294--4, Plastics — Injection moulding of test specimens of thermoplastic materials — Part 4:
cm + 4.9 cm + 5.6 cm + 6.3 cm + 7 cm
Determination of moulding shrinkage
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ISO 2577, Plastics — Thermosetting moulding materials — Determination of shrinkage
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ISO 5459, Geometrical product specifications (GPS) — Geometrical tolerancing — Datums and datum systems
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ISO 8015, Geometrical product specifications (GPS) — Fundamentals — Concepts, principles and rules
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3 Terms and definitions Formatted: Default Paragraph Font
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For the purposes of this document, the terms and definitions given in ISO 8015 and the following apply.
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ISO and IEC maintain terminologicalterminology databases for use in standardization at the following
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addresses:
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— — ISO Online browsing platform: available at https://www.iso.org/obphttps://www.iso.org/obp
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Not at 0.7 cm + 1.4 cm + 2.1 cm + 2.8 cm + 3.5 cm + 4.2
— — IEC Electropedia: available at https://www.electropedia.org/https://www.electropedia.org/
cm + 4.9 cm + 5.6 cm + 6.3 cm + 7 cm
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ISO/DIS FDIS 20457:2025(E2026(en)
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3.1 3.1
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product definition data set
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collection of one or more computer file(s) that discloses (directly or by reference), by means of graphic or
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textual presentations, or combinations of both, the physical and functional requirements of a product
Note 1 to entry: These are initially 3D data records and drawings as well as part lists. They might be supplemented by
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measuring and test specifications. 3D data records or drawings alone only fully describe plastic moulded parts in rare Adjust space between Asian text and numbers, Tab stops:
Not at 0.7 cm + 1.4 cm + 2.1 cm + 2.8 cm + 3.5 cm + 4.2
exceptional cases.
cm + 4.9 cm + 5.6 cm + 6.3 cm + 7 cm
Note 2 to entry: The aim of a specification is to describe the function completely with GPS characteristics (ISO 8015).
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This is done by means of references, direct tolerancing and general tolerances.
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[SOURCE: ISO 10209:2022, 3.1.70, modified — Notes 1 to entry have been added] Formatted: Default Paragraph Font
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3.2 3.2
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linear size
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dimensional parameter considered variable for a feature of size that can be defined on a nominal feature or
on an associated feature
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Note 1 to entry: A linear size is e.g. the diameter of a cylinder or the distance between two parallel opposite planes, two
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opposing lines, and two concentric circles. Depending on the type of linear feature of size, the terms “diameter”, “width”,
and “thickness” are synonyms for size. Distances in the sense of step dimensions are not size dimensions
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[SOURCE: ISO 14405-1:2025, 3.2, modified — Term changed from “size” to “linear size”, in Note 1 to entry the
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introductory phrase changed]
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3.3 3.3
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general tolerance
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tolerance on geometrical elements used as default, if the element has no direct tolerance (individual tolerance)
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4 Symbols and abbreviated terms
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4.1 General
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The symbols and abbreviated terms according to the ISO 1043 (all parts),series, ISO 18064 and the following
symbols and abbreviated terms apply for the application of this document. Formatted: Default Paragraph Font
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4.2 Symbols
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C tolerance mean dimension
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C tolerance mean dimension for moulded part application
A
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C tolerance mean dimension for moulded part production
F
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C tolerance mean dimension for tool contour production
W
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DP furthest distance in the space between the element to be toleranced and the origin of the datum
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system used for this positional tolerancing
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LF moulded part dimension Formatted
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L tool contour dimension .
W
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N nominal dimension for moulded part drawings
F
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ISO/FDIS 20457:2026(en)
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NW non-tool-specific dimensions
P total number of points
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P point evaluation of the individual influences
i
numbers
T tolerance Formatted Table
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t form and location tolerance
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numbers
T moulded part application tolerance
A
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T moulded part production tolerance
F
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T tool contour production tolerance
W
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SM moulding shrinkage
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𝑆𝑆 𝑆𝑆 moulding shrinkage transverse to the melt flow direction
M M⊥ Formatted
⊥
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𝑆𝑆 𝑆𝑆 moulding shrinkage parallel to the melt flow direction .
M M II
II
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𝑆𝑆 𝑆𝑆 ma ximum moulding shrinkage
M M ma
max
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𝑆𝑆 𝑆𝑆 mi nimum moulding shrinkage
M M min
min
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𝑆𝑆 𝑆𝑆 average calculated value for the moulding shrinkage Formatted
M M R
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R
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W tool-specific dimensions
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∆L dimensional shift
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∆L application-induced dimensional shift
A
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∆L moulding-induced dimensional shift
V
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∆S distribution of the moulding shrinkage Formatted Table
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∆S difference between VS 𝑉𝑉𝑆𝑆 and VS .
M II
⊥ ⊥
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ABF acceptance conditions for moulded part production
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ABW acceptance conditions for tool production Formatted
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GA maximum permissible deviation
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IRHD International Rubber Hardness Degree
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ISIR Initial Sample Inspection Report
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IT standard tolerance
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NW non-tool-specific dimensions
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TG tolerance grade
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W tool-specific dimensions
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ISO/DIS FDIS 20457:2025(E2026(en)
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5 Tolerancing of plastic moulded parts
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5.1 General
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and numbers
Relevant functions of the part shall be toleranced directly in order to enable the part manufacturer to optimize
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his manufacturing process accordingly. Secondary functions can be toleranced by means of the general
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tolerance.
Not at 0.71 cm
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Due to the special properties of plastic moulded parts, the following entries shall be made, where appropriate,
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in or on the title block in the product definition data set (drawing) in addition to the direct tolerancing, the
specification of the general tolerance class and the reference system for general tolerances:
— — for non-rigid parts: ISO 10579 -- NR, including additional restrained condition; Formatted: Default Paragraph Font
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— — if envelope principle is desired for linear size: Linear size ISO 14405 .
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Moulded part drawings or CAD data records correspond to the nominal geometry. The tolerances are
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symmetrical to the nominal geometry.
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cm + 4.9 cm + 5.6 cm + 6.3 cm + 7 cm
The procedure for the verification of tolerances shall be unambiguously defined and shall be a part of the
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contract. It is recommended to separate between Initial Sample Inspection Report (ISIR) and running
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production report (requalification). This may include or exclude the individual tolerances and general
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tolerances or specified functional tests (e.g. tightness, dielectric strength). If nothing has been stated in the
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contract, only individually indicated tolerances are subject for verification. The verification obligation of all
toleranced surfaces for the initial sample approval refers to the measurement within the scope of the initial
sample approval. This is to be stored as documented information.
Certain moulded parts, when removed from their manufacturing environment, can deform significantly from
their defined limits owing to their weight, flexibility or the release of internal stresses resulting from the
manufacturing processes.
Functionally reasonable references with adequate form stiffness shall be specified.
In the case of non-rigid parts, the measuring concept is of special importance (functional orientation, datum
system and overdetermination, gravitational influence, pretension, etc.). See also ISO 10579. Formatted: Default Paragraph Font
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For the orientation of the part, datum target points or small datum target areas shall be used instead of datum
features (e.g. complete planes).
Due to accuracy, integral references mustshall be created from reference points or as common references from
small geometry elements.
Figure 1Figure 1 a) shows a reference system of reference elements. This is not optimal for moulded parts due
to the draft angles, since the references are perpendicular to each other and thus only the edge is used for
slanted secondary or tertiary references. In Figure 1In Figure 1 b), the reference system is formed from
reference points. Since the moulded part is only aligned at points, the draft angles do not play a role. The design
in Figure 1Figure 1 c) also takes into account potential distortion of the surface at the primary reference (A--A)
and reduces the reference to three small raised surfaces.
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ISO/FDIS 20457:2026(en)
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a) Inadequat reference system from reference elements
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Not at 0.7 cm + 1.4 cm + 2.1 cm + 2.8 cm + 3.5 cm + 4.2
cm + 4.9 cm + 5.6 cm + 6.3 cm + 7 cm
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ISO/DIS FDIS 20457:2025(E2026(en)
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