GB/T 47067-2026Plastics moulded parts - Tolerances and acceptance conditions (English PDF)

Foreword

This document complies with the provisions of GB/T 1.1-2020 "Standardization Work Guidelines Part 1: Structure and Drafting Rules of Standardization Documents".

Drafting.

This document is modified to adopt ISO 20457:2018 "Tolerances and acceptance criteria for molded plastic parts".

This document has undergone the following structural adjustments compared to ISO 20457:2018.

---Note 3 in section 6.2 corresponds to note in ISO 20457:2018;

---Appendices B to H correspond to Appendices A to G in ISO 20457:2018.

This document differs significantly from ISO 20457:2018.The relevant clauses are indicated in vertical single lines on the blank pages outside the relevant sections.

The lines (|) are marked. A summary of these technical differences and their reasons is provided in Appendix A.

The following editorial changes have been made to this document.

---ISO 17450-1 (see 3.1, 7.1.1) has been replaced by GB/T 24637.1 (reference standard);

---ISO 17450-2 and ISO 17450-3 have been replaced with GB/T 24637.2 and GB/T 24637.3 (see GB/T 24637.2 for reference purposes).

---In ISO 20457:2018, note 3, change "see ISO 17450" to "see GB/T 38762.1-2020", and change the source to...

"GB/T 38762.1-2020, 3.4, with modifications" (see 3.2);

---The titles of Figures 2 and 3 have been updated with the symbols "y" and "x". In Figure 2, the dimension label has been changed from "x" to "y" (see 7.1.1);

---Added Appendix A (informative) "Technical differences between this document and ISO 20457:2018 and the reasons thereof".

Please note that some content in this document may involve patents. The issuing organization of this document assumes no responsibility for identifying patents.

This document was proposed by the China Petroleum and Chemical Industry Federation.

This document is under the jurisdiction of the National Technical Committee on Plastics Standardization (SAC/TC15).

Introduction

Compared to metals, plastics have higher deformability and lower rigidity, resulting in greater dimensional and shape deviations during the manufacturing of plastic molded parts.

Large, therefore, in order to economically manufacture molded parts while meeting functional requirements, during molding applications and/or molding processes (such as injection molding) Molding, compression molding, rotational molding), with relatively low precision requirements related to dimensional accuracy, and the evaluation of geometric tolerances of plastic molded parts and the quantification cannot be consistent with that of metallic materials, which is why this document was developed.

Due to the unique properties of plastics, it is necessary to consider the three different size reference grades defined in Appendix B, and to take into account the main influencing factors.

To be determined.

The following are the preferred steps to ensure effective collaboration when designing and developing plastic molded parts.

a) Designers of plastic molded parts determine the tolerances that meet the functional requirements based on application requirements, including function, operating environment, and assembly requirements.

Require.

b) To avoid unrealistic tolerances, plastic molding manufacturers must confirm that the selected manufacturing processes and raw material types meet the requirements.

Design tolerances must be met; otherwise, it will adversely affect economic or production efficiency. Tolerances with functional requirements are specified in the design document.

Defined in the document.

c) The design documents provide tolerance requirements to meet functional needs, thus providing a basis for determining the molding shrinkage rate. This also avoids...

The inability to meet functional tolerances results in excessive scrap and high costs. After the order is placed, the plastic mold...

The plastic parts manufacturer and the mold manufacturer or mold designer agree on the calculated value of the molding shrinkage rate, and if necessary, consult with the material supplier.

Negotiate with the supplier.

The dimensional control of plastic molded parts is mainly affected by the material, design, cavity layout, and processing technology.

In addition, other factors, including anisotropy, uneven wall thickness, and uneven cooling rates leading to warping/deformation and mold filling conditions, can also affect the mold.

Dimensions, integrity of molded plastic parts, and mechanical properties. Due to these factors and the complexity of polymer materials, their standardization is more stringent than that of traditional materials such as metals.

The materials are more complex. The dimensions of molded plastic parts may deviate due to unavoidable process factors. The procedures for handling these deviations depend on Whether the dimensional tolerance affects its normal use and the function of the plastic molded part shall be subject to the contract agreement.

---Eliminate deviations by optimizing the design (optimizing reinforcing ribs, material thickness, molding process, etc.).

--- Reduce deviations by optimizing the processing technology and procedures (such as extending the cooling cycle).

---Accepting the concession.

Concessionary acceptance requires the corresponding documentation, including drawing changes, manufacturing deviation documents, or updated reference plastic molded parts.

Note 1.Reduce process-related deviations by effectively designing plastic molded parts and optimizing production processes.

Note 2.Traditional tolerance calculations are based on rigid bodies and are not applicable to plastic molded parts in most cases.

Tolerances and acceptance criteria for plastic molded parts

1 Scope

This document specifies the manufacturing tolerances and acceptance conditions for plastic molded parts (hereinafter referred to as "molded parts").

This document specifies the general tolerances for all components, in a manner relative to the surface profile tolerances given by the datum system.

Additional requirements for dimensional and geometric tolerances are defined when using the Product Geometry Specification (GPS) based on functional requirements and design specifications.

This document applies to processes using thermoplastics, thermoplastic elastomers, and thermosetting plastics as raw materials, through injection molding, injection compression molding, and transfer molding.

Non-porous molded parts produced by die molding, compression molding, and rotational molding. This document also applies to the use of other production methods, provided that both the supplier and the buyer agree.

Molded parts manufactured using production processes. This document does not apply to molded parts made of foam plastics.

This document does not apply to surface defects in molded parts, such as shrinkage marks, abnormal flow structures, roughness, and weld lines.

2 Normative references

The contents of the following documents, through normative references within the text, constitute essential provisions of this document. Dated citations are not included.

For references to documents, only the version corresponding to that date applies to this document; for undated references, the latest version (including all amendments) applies.

This document.

GB/T 1800.1 Product Geometric Specification (GPS) - Linear Dimensional Tolerances - ISO Notation System - Part 1: Tolerances, Deviations and the basis for the coordination (GB/T 1800.1-2020, ISO 286-1:2010, MOD) GB/T 1800.2 Product Geometric Specification (GPS) - Linear Dimensional Tolerances - ISO Notation System - Part 2: Standard Tolerance Zones Codes and Limit Deviation Tables for Holes and Shafts (GB/T 1800.2-2020, ISO 286-2:2010, MOD) GB/T 1844 (all parts) Plastic symbols and abbreviations [ISO 1043 (all parts)] Note. GB/T 1844.1-2022 Plastics symbols and abbreviations – Part 1: Basic polymers and their characteristic properties (ISO 1043-1:2011, MOD);

GB/T 1844.2-2022 Plastics symbols and abbreviations – Part 2: Fillers and reinforcements (ISO 1043-2:2011, IDT);

GB/T 1844.3-2022 Plastic symbols and abbreviations – Part 3: Plasticizers (ISO 1043-3:2016, MOD);

GB/T 1844.4-2008 Plastic symbols and abbreviations - Part 4: Flame retardants (ISO 1043-4:1998, IDT).

GB/T 2918-2018 Standard environment for conditioning and testing of plastic specimens (ISO 291:2008, MOD) GB/T 4249 Product Geometry Specification (GPS) - Basic Concepts, Principles and Rules (GB/T 4249-2018, ISO 8015.

2011, MOD)

GB/T 13319 Product Geometric Technical Specification (GPS) - Geometric Tolerances for Groups (Elements) and Combinations GB/T 17037.4 Preparation of Injection Molded Specimens from Thermoplastic Materials - Part 4: Determination of Molding Shrinkage (GB/T 17037.4-2003, ISO 294-4:2001, IDT) GB/T 17851 Product Geometric Specification (GPS) - Geometric Tolerances and Datum System GB/T 17852 Product Geometric Specification (GPS) - Geometric Tolerances and Profile Tolerance Marking GB/T 22027 Nomenclature and Abbreviations for Thermoplastic Elastomers (GB/T 22027-2008, ISO 18064:2003, IDT) GB/T 24744 Designation of Molded Parts in Technical Product Documentation (TPD) - Product Geometry Specification (GPS) 2009, ISO 10135:2007, IDT) GB/T 38762.1 Product Geometric Specification (GPS) - Dimensional Tolerances - Part 1: Linear Dimensions (GB/T 38762.1-2020, ISO 14405-1:2016, MOD) GB/T 39818 Determination of shrinkage rate of thermosetting molding materials (GB/T 39818-2021, ISO 2577:2007) MOD)