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GB/T 14486-2008 PDF in English


GB/T 14486-2008 (GB/T14486-2008, GBT 14486-2008, GBT14486-2008)
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GB/T 14486-2008: PDF in English (GBT 14486-2008)

GB/T 14486-2008
GB
NATIONAL STANDARD OF THE
PEOPLE’S REPUBLIC OF CHINA
ICS 83.080; 83.080.01
G 31
Replacing GB/T 14486-1993
Dimensional tolerances for moulded plastic parts
ISSUED ON. AUGUST 14, 2008
IMPLEMENTED ON. APRIL 1, 2009
Issued by. General Administration of Quality Supervision, Inspection
and Quarantine of the People’s Republic of China;
Standardization Administration of the People’s Republic of
China.
Table of Contents
Foreword ... 3 
Introduction ... 5 
1 Scope ... 6 
2 Normative references ... 6 
3 Terms and definitions ... 7 
4 Basic provisions ... 8 
5 Inspection methods ... 13 
6 Indication of the dimensional tolerances ... 14 
Appendix A (Normative) Selection method for the tolerance grades of
moulded plastic parts ... 15 
Foreword
The consistent degree between this Standard and DIN 16901.1982 (German
national standard) Plastics mouldings – Tolerances and acceptance
conditions for linear dimensions is not equivalent. The major differences are
as follows.
a) The basic dimension segments are different. The basic dimension
segments in this Standard are the same with those in the ISO
286-1.1988. 28 dimension segments are divided within the range of
0mm to 1,000mm, while there are only 21 dimension segments in the
German standard.
b) There are differences in the relationship between tolerance values and
dimension values. Under the corresponding grade of precision, the
tolerance values in these two standards are approximate within the
small dimension range of 0mm to 100mm. Several tolerance values in
the German standard are a little less than those in this Standard.
However, within the large dimension range, the situation is just the
opposite – the tolerance values in this Standard are less than those in
the German standard. In terms of precision, the grade of precision in this
Standard is about half a grade higher than that in the German standard.
This Standard replaces GB/T 14486-1993 Dimensional tolerances for plastic
engineering moulded plastic parts.
Compared with the GB/T 14486-1993, the major differences are as follows.
a) RENAME this Standard FROM Dimensional tolerances for plastic
engineering moulded plastic parts TO Dimensional tolerances for
moulded plastic parts.
b) The tolerance values in the original national standard GB/T 14486-1993
are generally less than those of the products with the same precision
and dimensions in the German industry standard DIN 16901. However,
there are also some opposite situations within the range of 0mm to
100mm. During the revision, it partially refers to the smaller tolerance
values in the German industry standard, so as to adapt to the current
situation and requirements that the precision of plastic parts has been
increasingly improved.
c) EXPAND the dimension range in the tolerance table from “0mm~500mm”
to “0mm~1,000mm”. ADD the corresponding tolerance values.
Dimensional tolerances for moulded plastic parts
1 Scope
This Standard specifies the dimensional tolerances for the moulded plastic
parts made from thermosetting and thermoplastic materials (hereinafter
referred to as “moulded plastic parts”).
This Standard is applicable to the moulded plastic parts produced by
injection moulding, compression moulding, transfer moulding and cast
moulding, and is not applicable to extrusions, blow-moulded parts, sintered
parts and foamed mouldings.
2 Normative references
The provisions in the following documents become the provisions of this
Standard through reference in this Standard. For dated references, the
subsequent amendments (excluding corrections) or revisions do not apply to
this Standard. However, parties who reach an agreement based on this
Standard are encouraged to study if the latest versions of these documents
are applicable. For undated references, the latest versions apply to this
Standard.
GB/T 1800.2-2008 [Translator note. the standard number should be “GB/T
1800.2-2009”.] Geometrical product specifications (GPS) – Limits and fits –
Part 2. Tables of standard tolerance grades and limit deviations for holes
and shafts (ISO 286-2.1988, MOD)
GB/T 1844.1-2008 Plastics – Symbols and abbreviated terms – Part 1.
Basic polymers and their special characteristics (ISO 1043-1.2001, IDT)
GB/T 2035-2008 Terms and definitions for plastics (ISO 472.1999, IDT)
GB/T 2918-1998 Plastics – Standard atmospheres for conditioning and
testing (idt ISO 291.1997)
GB/T 17037.4-2003 Plastics – Injection moulding of test specimens of
thermoplastic materials – Part 4. Determination of moulding shrinkage
(ISO 294-4.2001, IDT)
3 Terms and definitions
The terms, definitions and symbols specified in the GB/T 2035-2008 and the
following ones apply to this Standard.
3.1 Moulding shrinkage
SM
It refers to the ratio OF the difference between the dimensions of the
moulding chamber Lm and those of the corresponding moulded plastic part Lp
TO the dimensions of the moulding chamber Lm at (23 ± 2) °C, expressed as
percentage.
Where.
SM – Moulding shrinkage, %;
Lp – The dimensions of the moulded plastic part that has been placed in the
standard atmosphere for 24h after the moulding of the plastic part, in unit
of millimeter (mm);
Lm – The corresponding dimensions of the moulding chamber, in unit of
millimeter (mm).
3.2 Moulding shrinkage in flow direction
SMp
It refers to the moulding shrinkage along the material flow direction during
moulding.
3.3 Moulding shrinkage in transverse direction
SMn
It refers to the moulding shrinkage perpendicular to the flow direction during
moulding.
3.4 Difference of moulding shrinkage in flow and transverse directions
△SM
It refers to the difference of moulding shrinkage in flow and transverse
directions during moulding.
PUR-P Thermoplastic polyurethane MT4 MT5 MT7
PVC-P Plasticized polyvinylchloride MT5 MT6 MT7
PVC-U Unplasticized polyvinyl chloride MT2 MT3 MT5
SAN (Acrylonitrile-styrene) copolymers MT2 MT3 MT5
UF Urea-formaldehyde resin
With inorganic filler MT2 MT3 MT5
With organic filler MT3 MT4 MT6
UP Unsaturated polyester With 30% glass fiber filler MT2 MT3 MT5
4.3 Dimensions with tolerance indications
For the tolerance grades of the dimensions with tolerance indications, SEE
Table 2. The listed numerical values correspond to the tolerance grades in
Table 1.
This Standard only specifies tolerances. The upper and lower deviations of
basic dimensions can be divided according to the actual engineering needs.
For instance, the tolerance 0.8 can be divided into. , , ± 0.4,
or , etc.
4.4 Dimensions without tolerance indications
For the tolerance grades of the dimensions without tolerance indications,
SEE Table 2. The listed numerical values correspond to the tolerance grades
in Table 1.
4.5 Dimension a not affected by the movable parts of the mould
The dimensions not affected by the movable parts of the mould in Table 1
refer to the dimensions moulded by the same mould part in the mould. For
instance, the radial dimensions of the moulded parts with integral cavities.
SEE Figure 1.
Appendix A
(Normative)
Selection method for the tolerance grades of moulded plastic parts
SELECT the tolerance grades according to the shrinkage property values of
moulding materials. SEE Table A.1.
Table A.1 Shrinkage Property Values of Moulding Materials and
Selected Tolerance Grades
Shrinkage property value
vS
/ %
Tolerance grade
Dimensions with tolerance indications Dimensions without
tolerance indications High precision General precision
> 0~1 MT2 MT3 MT5
> 1~2 MT3 MT4 MT6
> 2~3 MT4 MT5 MT7
> 3 MT5 MT6 MT7
......
 
Source: Above contents are excerpted from the PDF -- translated/reviewed by: www.chinesestandard.net / Wayne Zheng et al.