GB/T 42869-2023Requirements for three-dimensional model simplification and lightweight of mechanical products (English PDF)

Foreword

This document was issued on 6 August 2023 by the State Administration for Market Regulation; Standardization Administration of the PRC and takes effect on 1 December 2023.

It is a GB/T standard: recommended rather than compulsory, but it is the text a Chinese reviewer applies when assessing a submission.

1 Scope

GB/T 42869-2023 covers the simplification and the lightweighting of three-dimensional models of mechanical products — the two operations by which a full-detail design model is reduced to something a downstream user can actually open and work with. After the terms and the abbreviations, the simplification clause is organised by where the reduction happens: general requirements first, then part modelling, assembly model applications, finite element modelling, and models prepared for issue. The lightweighting clause follows the same pattern but by purpose: general requirements, collaborative research and development, assembly simulation, three-dimensional process documents, three-dimensional electronic interactive publications, and visual display. Two informative annexes give worked examples of each operation. The problem behind that structure is that one model serves audiences with opposite needs. A simulation model wants small features gone; a supplier needs geometry that still measures correctly; a service publication needs a file that opens on an ordinary laptop. Left to individual judgement, each group reduces the model in its own way, the versions drift apart, and nobody can say afterwards which of them the released drawing was made from. It is used by design and simulation teams, CAD and product data management administrators, technical publication groups, and the software vendors whose export settings have to answer these categories.

This document specifies the requirements for simplification and lightweight of three-

dimensional models of mechanical products.

This document is suitable for three-dimensional model construction of mechanical

products and simplification and lightweight processing in application scenarios such as

simulation, visualization, data sharing and exchange.

2 Normative references

The following referenced documents are indispensable for the application 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.

GB/T 24734.11, Technical product documentation -- Digital product definition data

practices -- Part 11: Levels of geometrical detail

GB/T 26099.1, General principles of three-dimensional modeling for mechanical

products -- Part 1: General requirements

GB/T 26099.2, General principles of three-dimensional modeling for mechanical

products -- Part 2: Part modeling

GB/T 26099.3, General principles of three-dimensional modeling for mechanical

products -- Part 3: Assembly modeling

GB/T 26100, General principles of digital mock-up for mechanical products

3 Terms and definitions

For the purposes of this document, the terms and definitions defined in GB/T 26099.1,

GB/T 26099.2, GB/T 26099.3, GB/T 26100 as well as the followings apply.

3.1 simplification

A three-dimensional model construction or processing method that allows certain

features not to be constructed, certain parts or components not to be assembled,

f) Name the simplified model file in accordance with the provisions of GB/T 26099.1.

Consider the inheritance with the original model name.

5.2 Simplification requirements in part modeling

5.2.1 Three-dimensional model simplification in part modeling meets the following

requirements:

a) The external interface of the model shall not be simplified and its assembly shall

not be affected;

b) Some features related to manufacturing, such as internal threads, external threads,

undercuts, etc., are allowed to be omitted or simplified in expression. However,

when the simplified model is used for projection to generate two-dimensional

engineering drawings, it shall meet the relevant regulations of mechanical

drawing;

c) For several groups of holes with the same diameter and distributed in a certain

regular pattern, only one feature can be constructed. Other similar features can be

simplified by the center line;

d) Features such as printing, engraving, and knurling allow simplified expression in

the form of stickers. When necessary, it can also be accompanied by comments;

e) When modeling standard parts and purchased parts, the internal structure

unrelated to installation is allowed to be simplified, but basic information that

affects the model assembly design such as the maximum geometric outline,

installation interface, extreme position, and mass attributes shall be included;

f) Under the conditions that meet the usage requirements, low-order surfaces can be

used instead of high-order surfaces.

5.2.2 See Figure A.1 in Annex A for a simplification example in part modeling.

5.3 Simplification requirements for assembly model applications

5.3.1 Three-dimensional model simplification for assembly model applications meets

the following requirements.

a) When assembly models are used for visual display, such as in digital factories or

digital production line visual display applications, for assembly models of

production lines, machine tools, logistics and other equipment, if the internal

details do not need to be displayed, a simplified method without assembly can be

used. If some external subtle features do not affect the display effect, simple

shapes (cylinder, cube, etc.) can be used instead of the simplified method of

complex shapes.

b) Generally, it is advisable to remove the modeling history information in the

original model and base it on the business needs of different application scenarios

in a). Choose to retain, partially remove or completely remove assembly structure,

annotations, attributes, views, colors and other information;

c) The lightweight model formed after surface processing can reduce the size of the

model file through surface reduction, merging primitives, deleting invisible

surfaces, patching or deleting holes, etc., so as to meet the requirements of the

visualization software and hardware system;

d) For point cloud models obtained by reverse engineering methods, it is advisable

to convert mesh surfaces into NURBS surfaces or other parameter expressions to

reduce model file size;

e) For a large number of repeated parts, only the geometric data of one part can be

recorded, but the position information of all parts shall be saved to reduce the

amount of data. At the same time, the recorded geometric data information of the

parts and all parts shall be used during the visualization process. location

information to reconstruct all parts and position them correctly;

f) Multiple LOD level representations shall be provided to meet visualization and

accuracy requirements;

g) The lightweight model file naming shall be in accordance with the provisions of

GB/T 26099.1. Consider inheritance from the original model’s name.

6.2 Lightweight requirements for collaborative research and development

The lightweight of three-dimensional models in collaborative R&D applications meets

the following requirements:

a) It shall be based on the needs of product data sharing and exchange, browsing and

circle reading in collaborative R&D applications. Determine the lightweight

model file format. Choose lightweight processing tools;

b) The lightweight model file format, unit system and scale shall be consistent.

Model accuracy shall meet the requirements of all parties involved in

collaborative R&D;

c) The assembly structure information in the original model shall be included;

d) Annotations and marking information shall be saved in lightweight model files.

6.3 Lightweight requirements for assembly simulation

The lightweight three-dimensional model for assembly simulation applications shall

meet the following requirements:

a) According to the assembly process simulation in assembly simulation applications,

as well as the interference inspection and simulation requirements between

components, between components and tooling, determine the lightweight model

file format and select lightweight processing tools;

b) Contain assembly structure and assembly relative position information in the

original model.

6.4 Lightweight requirements for three-dimensional processes

Three-dimensional model lightweight for three-dimensional processes shall meet the

following requirements:

a) According to the process model visual display and human-computer interaction

requirements in three-dimensional process visualization publishing applications,

the lightweight model file format is determined. Choose lightweight processing

tools;

b) Contain assembly structure, annotations, attributes, views, colors and other

information in the original model.

6.5 Lightweight requirements for three-dimensional electronic interactive

publications

The lightweight three-dimensional model for three-dimensional electronic interactive

publications shall meet the following requirements:

a) The lightweight model file format is determined based on the model-based product

installation, use, repair and maintenance interaction requirements and the type of

interactive display platform in the three-dimensional electronic interactive

publication application. Choose lightweight processing tools;

b) Contain assembly structure, annotations, attributes, views, colors and other

information in the original model.

6.6 Lightweight requirements for visual display

The lightweight three-dimensional model for visual display shall meet the following

requirements:

a) According to the purpose of visual display, such as concept display before product

manufacturing, publicity display after product manufacturing, and training

display such as operation/maintenance, as well as the software and hardware

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