ISO 20457:2018

INTERNATIONAL ISO
STANDARD 20457
First edition
2018-09
Plastics moulded parts — Tolerances
and acceptance conditions
Moulages plastiques — Tolérances et conditions de réception
Reference number
©
ISO 2018
© ISO 2018
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ii © ISO 2018 – All rights reserved

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 Intention . 4
5.3 General tolerances . 5
5.4 Direct tolerancing (individual tolerancing) . 5
5.5 Tolerancing of draft angles . 5
5.6 Dimensioning, tolerancing and measuring of radii . 6
5.7 Specification of freeform surfaces . 6
6 Moulding compound properties . 6
6.1 General . 6
6.2 Moulding shrinkage and shrinkage anisotropies . 6
6.3 Moulded material stiffness or hardness. 8
7 Dimensional and geometrical tolerancing . 8
7.1 Dimensional tolerancing. 8
7.1.1 Tolerance grades for features of sizes . 8
7.1.2 Determination of the tolerance grades .11
7.2 Geometrical tolerancing .14
7.3 Parting line/Tool offset .16
7.4 Tolerancing of angular dimensions .17
8 Acceptance conditions for moulded part production (ABF) .17
Annex A (informative) Dimensional reference levels for application and production of the
moulded parts .18
Annex B (informative) Causes and influential factors on the moulding shrinkage of non-
porous plastics .20
Annex C (informative) Evaluation of the production expense .21
Annex D (informative) Validation of machine or process capability .24
Annex E (informative) Main causes for dimension, form and location deviations in moulded
part production .25
Annex F (informative) Example for determining the D dimension for application of Table 9 .26
P
Annex G (informative) Feasible acceptance parameters .27
Bibliography .28
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 documents 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).
Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights. ISO shall not be held responsible for identifying any or all such patent rights. Details of
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on the ISO list of patent declarations received (see www .iso .org/patents).
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constitute an endorsement.
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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.
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 2018 – All rights reserved

Introduction
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 should always be defined in the design
documentation.
c) The functionally required tolerances should always be defined in the design documentation 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 cost. After order placement, calculated values with respect to
the moulding shrinkage should 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.
The acceptance of non-conformance requires appropriate documentations including drawing
corrections, production deviation documentations or updated reference parts.
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 © ISO 2018 – All rights reserved

INTERNATIONAL STANDARD ISO 20457:2018(E)
Plastics moulded parts — Tolerances and acceptance
conditions
1 Scope
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.
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 286-1, Geometrical product specifications (GPS) — ISO code system for tolerances on linear sizes —
Part 1: Basis of tolerances, deviations and fits
ISO 286-2, Geometrical product specifications (GPS) — ISO code system for tolerances on linear sizes —
Part 2: Tables of standard tolerance classes and limit deviations for holes and shafts
ISO 291:2008, Plastics — Standard atmospheres for conditioning and testing
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 8015, Geometrical product specifications (GPS) — Fundamentals — Concepts, principles and rules
ISO 10135, Geometrical product specifications (GPS) — Drawing indications for moulded parts in technical
product documentation (TPD)
ISO 14405-1, Geometrical product specifications (GPS) — Dimensional tolerancing — Part 1: Linear sizes
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 terminological databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https: //www .iso .org/obp
— IEC Electropedia: available at http: //www .electropedia .org/
3.1
design documentation
documents and data necessary for complete structural description of components, assemblies or
machines and devices
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: For further information, see ISO 17450-1, ISO 17450-2 and ISO 17450-3.
3.2
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: In this document, the size is linear, 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.
Note 2 to entry: A size is angular (e.g. angle of a cone) or linear (e.g. diameter of a cylinder). This document only
deals with linear size.
Note 3 to entry: For further information on linear size, see ISO 17450.
[SOURCE: ISO 17450-1:2011, 3.4, modified — References to ISO 14405 have been replaced with “this
document” and a Note 3 to entry has been added.]
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 ISO 1043, 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
P
datum system used for this positional tolerancing
L moulded part dimension
F
L tool contour dimension
W
N nominal dimension for moulded part drawings
F
2 © ISO 2018 – All rights reserved

P total number of points
g
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
VS moulding shrinkage
moulding shrinkage transverse to the melt flow direction
VS
⊥
VS moulding shrinkage parallel to the melt flow direction
II
VS maximum moulding shrinkage
max
VS minimum moulding shrinkage
min
VS average calculated value for the moulding shrinkage
R
∆L dimensional shift
∆L application-induced dimensional shift
A
∆L moulding-induced dimensional shift
V
∆S distribution of the moulding shrinkage
∆VS
difference between VS and VS
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
IT standard tolerance
NW non-tool-specific dimensions
TG tolerance grade
W tool-specific dimensions
5 Tolerancing of plastic moulded parts
5.1 General
The independency principle according to ISO 8015 applies when using this document.
Change of the default specification operator for size shall be indicated on the drawing in or near the
title block according to ISO 14405-1, e.g. “Linear size ISO 14405 E” for the envelope principle.
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 ISIR (Initial Sample Inspection Report) 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.
Unless otherwise defined or by agreement, plastic moulded parts, in which the general tolerances are
not met, do not have to be automatically rejected if the functionality of the part is not compromised.
Certain 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 have to 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 have to be used instead
of datum features (e.g. complete planes).
NOTE The datum system reflects the orientation of the part in the assembly. It is important that the datum
system is stable.
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.
A standard atmosphere in the plastic range is 23 °C ± 2 K and 50 % ± 10 % relative air humidity as
defined in ISO 291.
5.2 Intention
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).
Figure 1 gives an overview about the intentions and about the composition of tolerance.
4 © ISO 2018 – All rights reserved

Figure 1 — 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 General tolerances
Only series 1 (simple production) according to Table 8 applies for general tolerances. General tolerances
shall be indicated in or near the title block.
EXAMPLE General tolerances ISO 20457:JJJJ – TG6.
General tolerances for size apply only on explicitly drawn dimensions on the drawing indicated without
direct tolerances (individual tolerances). General tolerances for positions apply to features of sizes with
respect to the master datum system only.
Profile tolerances of a surface shall be applied as general tolerances, specified in detail in the drawing,
restricting all 6 degrees of freedom.
General tolerances for features of linear size apply only on explicitly drawn nominal dimensions in the
drawing.
5.4 Direct tolerancing (individual tolerancing)
Tolerances (dimensional or geometrical) for functional elements/dimensions shall be explicitly
specified.
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.
5.5 Tolerancing of 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
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 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.
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 a surface profile tolerance. The verification shall
be fixed in the contract between producer and costumer.
6 Moulding compound properties
6.1 General
This document does not contain any type lists for moulding compounds or their assignment to
attainable production accuracies. Accuracy-relevant properties shall be considered in order to indicate
a general assignment scheme for the large number and variety of moulding compounds.
6.2 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
F
until measurement and measured according to ISO 291:2008, Table 1, unless otherwise specified by
contract or the relevant ISO-material specification. It is calculated according to Formula (1).
 
L
F
VS =−1 ×100% (1)
 
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 is 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.
6 © ISO 2018 – All rights reserved

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).
DVS =−IV��SVSI (2)
⊥ II
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
DSV=−SVS (3)
maxmin
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
R
and sampling of the tools. It is calculated according to Formula (4).
VS =+05, VS VS (4)
()
Rmax min
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.
NOTE 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.
6.3 Moulded material stiffness or hardness
The elastic recovery (relaxation) of the moulding material after removal of the part has a significant
effect on the linear and angular sizes and dimensions. The required data shall be provided in the
specifications of the raw material suppliers.
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 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 (International Rubber Hardness Degree). All
tests refer to 23 °C and normally conditioned test specimens.
7 Dimensional and geometrical tolerancing
7.1 Dimensional tolerancing
7.1.1 Tolerance grades for features of sizes
In order to approximately adapt the distribution of the production tolerances resulting from the
moulding compound and process, and their particular nominal dimensional relation for plastic
moulded parts to the ISO system for limit dimensions and fits according to ISO 286-1 and ISO 286-2,
nine tolerance grades (TG1 to TG9) in three nominal dimension ranges were assigned to the ISO basic
tolerance grades (IT) for tool-specific dimensions in 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 limit dimensions 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
(Figure 2 and Figure 3).
8 © ISO 2018 – All rights reserved

Key
1 closing direction
2 movement direction of the slide
Figure 2 — Tool-specific dimensions
Key
1 closing direction
2 movement direction of the slide
Figure 3 — Non-tool-specific dimensions
10 © ISO 2018 – All rights reserved
Table 2 — Plastic moulded part tolerances as symmetrical limit dimensions for features of sizes
Dimensions in mllimetres
Limit dimensions (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
F F
other directly but are arranged shifted to one another, 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 design documentation as follows. Example: ISO 20457:JJJJ-MM – TG6.
NOTE 8  For validation of machine and process capability, see Annex D.

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
i g
Table 3 (exception is 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 4 shows an overview of the process to determine the tolerance grade.
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 4 — 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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Table 5 — Evaluation matrices 2
a
Moulded material stiffness or hardness
Modulus of elasticity Shore D Shore A; IRHD
P
N/mm
above 1 200 above 75 — 1
above 30 to 1 200 above 35 to 75 — 2
3 to 30 — 50 to 90 3
below 3 — below 50 4
a
Modulus of elasticity: dry as moulded.
Table 6 — Evaluation matrices 3
Moulding shrinkage (calculated value) P
below 0,5 % 0
0,5 % to 1 % 1
above 1 % to 2 % 2
above 2 % 3
The maximum shrinkage characteristic value is definitive for the assignment in the case of shrinkage anisotropy.
Table 7 — Evaluation matrices 4
Consideration of the shrinkage differences due to geometry and process P
Precisely possible:
Calculated values of the VS are known. (For example from experience, systematic measurements, com-
puter simulations.) Shrinkage anisotropy is meaningless or can be considered sufficiently accurately
in the relevant dimensional orientation. Possible deviations from the calculated value are max. ±10 %.
Precisely possible with limitations:
Calculated values of the VS are known in ranges max. to ±20 %.
Only imprecisely possible:
Calculated values of the VS are only known as rough guide values ranges. Shrinkage anisotropy cannot
be considered or can only be considered inadequately. Practical experience for estimating relevant
calculated values is not available. Possible deviations from the calculated value are above ±20 %.
In general, it is assumed that the shrinkage fluctuations due to variations in the processing conditions and differences in
the moulding compound properties can be approximately ±30 % of the calculated value of the VS. The selection P = 3 is to
be made if no other information is available.
After determining P to P and their addition, it should be checked whether the structurally required
1 4
tolerance can be attained technologically with series 1 (simple production). If this is fulfilled, all further
considerations will be sufficient. The increase in the production expense contained in P only has to be
considered if the functionally required tolerance is not attained.
7.1.2.3 Evaluation of the production expense (P )
The expense necessary for the moulded part manufacturer for production and quality assurance
is definitive for the level of the production accuracy. The differentiation is made by the application/
utilization of the tolerance rows (see Table 8).
Table 8 — Evaluation of the production expense
Tolerance series P
Series 1 (simple production)
Production realized with general tolerances. Dimensional stability requirements that do not form any
special quality focus.
Series 2 (accurate production)
−1
Production and quality assurance are oriented to higher dimensional stability requirements.
Series 3 (precision production)
−2
Full alignment of production and quality assurance to the very high dimensional stability requirements.
Series 4 (precision special production)
−3
As series 3, but with more intensive process monitoring.
The tolerance Series 3 (precision production) and Series 4 (precision special production) are always subject to mandatory
agreement.
Exemplary selection criteria are listed in Annex C to assist the series assignment.
NOTE If a higher accuracy level (Series 2, Series 3 and Series 4) is necessary for directly toleranced
dimensions, the rows assignment are to be performed after evaluation of the necessary fulfilment degree of the
questions below:
— Are the moulded parts optimally designed and dimensioned in respect to dimensional stability?
— Are the moulds functionally reliable and consistent in respect to mechanical and thermal control?
— For complex or multi-cavity moldings, are fill patterns uniform throughout the mould or between cavities?
— Are adequate systems in place to monitor and document material handling, moulding, and quality control
systems?
— Are operating and quality control personnel adequately trained to ensure quality assurance and conformance?
— Are corresponding terms of delivery agreed in respect to the dimensionally-relevant properties level of the
moulding compounds, in particular the shrinkage fluctuations, and are these checked?
The actual effort to realizethe part by the moulded part manufacturer is derived from the required
dimensional tolerances. Precision productions (Series 3 and Series 4) are special cases whose realization
might require special agreements between the buyer and manufacturer of the moulded parts from an
economic operational viewpoint (e.g. price surcharges) as well. It should therefore be expressly noted
that unnecessarily high tolerance requirements lead to unnecessarily high moulded part costs.
7.2 Geometrical tolerancing
ISO 1101 and ISO 5458 in a datum system according to ISO 5459 apply for surface profile and line profile
and position tolerances.
A component can have one or more datum systems. The furthest distance of the toleranced element
to the origin of the datum system used for the position tolerance D shall be applied to determine the
P
position tolerance. This does not have to correspond to the coordinate system of the component or from
the assembly. The D dimension is the nominal dimension for determination of the position tolerance
P
according to Table 9. The same also applies to profile form tolerances according to Table 10.
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