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This standard was proposed by the China National Automotive Industry Corporation.
This standard is under the jurisdiction of China Automotive Technology and Research Center.
Dimension limit deviations of automotive molded plastic parts without tolerance indications
1 Content and scope
This standard specifies the dimension limit deviations of automotive molded plastic parts without tolerance indications.
This standard is applicable to the dimension of thermosetting plastic and thermoplastic parts formed by molding, injection and casting without tolerance indications.
This standard is not applicable to the dimension of plastic parts manufactured by extrusion, blow molding, cold drawing, sintering and foaming processes without tolerance indications.
2 Normative references
ZB T04 006.2 Dimension limit deviations of automotive cutting parts without tolerance indications
3 Terms
Molding shrinkage V: difference between the dimension Lw of mold in standard atmosphere and the dimension LF of molded part measured after being placed in the standard atmosphere with a temperature of 23±2℃ and a relative humidity of (50±2)% for 24 h.
V＝LW-LF (1)
Molding shrinkage rate VS: calculated using Formula (2).
(2)
Radial molding shrinkage rate VSR: molding shrinkage rate in the direction of injection.
Tangential molding shrinkage rate VST: molding shrinkage rate in the direction perpendicular to injection direction.
Molding shrinkage rate difference ΔVS: difference between radial molding shrinkage rate and tangential molding shrinkage rate.
ΔVS＝VSR-VST (3)
Shrinkage characteristic value: value corresponding to the sum (absolute value) of radial molding shrinkage rate and molding shrinkage rate difference of the molded part, as shown in Table 1.
Table 1
Sum (absolute value) of radial molding shrinkage rate and molding shrinkage rate difference, % Shrinkage characteristic value and its grading
4 Dimensions classification of molded plastic parts without tolerance indications
Dimensions of molded plastic parts without tolerance indications are divided into two classes:
Class a consists of dimensions constrained by single mold, while Class b consists of dimensions not constrained by single mold, as shown in Figure 1:
a—dimension constrained by single mold b—dimension not constrained by single mold
Figure 1
5 Dimension limit deviations of molded plastic parts without tolerance indications
As specified in Table 2.
Foreword i
1 Content and scope
2 Normative references
3 Terms
4 Dimensions classification of molded plastic parts without tolerance indications
5 Dimension limit deviations of molded plastic parts without tolerance indications
6 Limit deviations of thread length, inclination angle and fillet radius of molded plastic parts without tolerance indications
Annex A Corresponding relation between molded plastic materials and their shrinkage characteristic values (Supplement)
