GB/T 39252-2020Additive manufacturing—Specification for powder bed fusion process of metal materials (English PDF)

4.2.3 Maintenance

4.2.3.1 The operator shall develop a maintenance plan according to the instruction manual of the powder bed fusion equipment, and the maintenance content shall be carried out in accordance with the instruction manual provided by the equipment manufacturer or relevant standards.

4.2.3.2 Energy sources, scanning systems, etc. shall be calibrated regularly.

4.2.3.3 Maintenance or calibration results shall be recorded, and the record retention time shall be in accordance with the instructions for use provided by the equipment manufacturer.

4.3 Feedstock

4.3.1 Performance

The main performance indicators of metal powder include chemical composition, particle size and particle size distribution, fluidity, oxygen content, sphericity rate, bulk density, hollow powder rate, etc. The grade and chemical composition of metal powder shall meet the requirements of relevant standards, or be determined by negotiation between the supplier and the buyer before manufacturing. Metal powder inspection indicators shall be determined according to process requirements, and other special requirements need to be determined through negotiation between the supplier and the buyer. Unless determined through negotiation between the supply and demand parties, the inspection method shall be implemented in accordance with the requirements specified in GB/T 35022.

4.3.2 Reuse

The used powder can be reused or mixed after being sieved and tested to meet the requirements of 4.3.1, and the batch number shall be re-programmed, indicating the number of reuses and mixing ratio. The screen shall comply with the provisions of GB/T 6003.1; if the used powder after screening does not meet the requirements of 4.3.1, the supply and demand parties shall negotiate to determine its use or environmentally friendly disposal.

4.3.3 Delivery and storage

4.3.3.1 The powder supplier shall provide the safety technical instructions and quality certificate of the powder. The quality certificate shall include but not be limited to the powder grade, batch number, physical and chemical properties, and other indicators.

4.3.3.2 Powder should be stored in closed, anti-static, flame-retardant containers in a dry, cool, non-corrosive environment. Powder storage shall be carried out in accordance with the environmental conditions provided by the powder supplier.

4.3.3.3 Necessary measures shall be taken to prevent powder from being contaminated during use, storage, transportation, screening, cleaning, etc.

4.4 Environment

4.4.1 Working environment

The recommended working environment for powder bed fusion equipment and powders is as follows:

a) Ambient temperature: 5 °C~35 °C;

b) Relative humidity: <=75%.

4.4.2 Site requirements

The site where the equipment is installed shall have good ventilation and lighting conditions and shall be implemented in accordance with the regulations of GB 50019. The ground-bearing capacity shall comply with the equipment manufacturer's requirements.

4.4.3 Magnetic field

Magnetic field requirements mainly apply to powder bed melting equipment using electron beams as energy sources. The magnetic field strength of the environment in which they are located shall not affect the electron beam focusing and scanning deflection control.

4.5 Security

4.5.1 The safety protection of powder bed fusion equipment using laser as an energy source shall comply with the regulations of GB 25493.

4.5.2 The explosion-proof pressure relief device of the build chamber of the powder bed fusion equipment using laser as the energy source shall comply with the regulations of GB/T 15605.

4.5.3 The electromagnetic radiation surrounding the powder bed fusion equipment using electron beams as the energy source shall comply with the regulations of GB 8702.

4.5.4 Powder bed fusion equipment shall be well grounded.

4.5.5 The explosion-proof safety of powder operations during use, storage, cleaning,

5.2 Model design

5.2.1 Designers can obtain part models through three-dimensional software modeling or scanning entities.

5.2.2 The model design of parts shall comply with the relevant provisions of GB/T 37698.

5.3 Data processing and process parameter setting

5.3.1 Data processing shall include but not be limited to file editing, format conversion, support design, slicing, scan path planning, etc.

5.3.2 The format of the data file shall comply with the equipment requirements, and the model file shall be in a format that can be recognized by the powder bed fusion equipment software, such as STL, AMF, 3MF, and OBJ. When performing data processing (such as format conversion and slicing), the operator shall ensure that the data is not lost and traceable and the relevant content is fully recorded. For the recorded content, see Appendix A.

5.3.3 The building orientation and placement shall be determined based on factors such as the part's structure, performance requirements, forming time, support removal, and ease of powder cleaning. At the same time, the gaps between the parts shall be checked to ensure that the parts do not interfere with each other.

5.3.4 For parts that require the addition of support structures, factors such as the type, quantity, and removal of supports shall be considered.

5.3.5 The specimen can be taken directly from the part, or the sample along with parts can be built separately.

5.3.6 The number, building orientation, and placement of the sample along with parts shall be determined.

5.3.7 The orientation and position description of parts and test specimens shall comply with the regulations in ISO/ASTM 52921.

5.3.8 To set the corresponding parameters according to the material type and part performance, please refer to the process parameter package provided by the powder bed fusion equipment manufacturer.

5.4 Forming preparation

5.4.1 Feedstock

Feedstocks used for forming manufacturing shall comply with the requirements of 4.3.

5.4.2 Protective gas Whether

protective gas (such as nitrogen, argon, and helium) is needed is determined based on process requirements. When a protective gas is used, its purity shall be no less than 99.9%.

5.4.3 Equipment

5.4.3.1 Powder bed fusion equipment shall be in good condition.

5.4.3.2 The material of the build platform shall have good metallurgical compatibility with the feedstocks, and the thickness, flatness, and roughness shall meet the process requirements. Impurities and oil stains on the surface shall be removed before use. After the build platform is installed and fixed as required, the parallelism and distance between the build platform and the powder spreader shall comply with the regulations of the powder bed fusion equipment manufacturer.

5.4.3.3 The build chamber shall be cleaned before powders of different grades or batches are added to avoid cross-contamination.

5.4.3.4 The protective gas type, oxygen content, vacuum degree (electron beam), gas pressure and build platform preheating temperature of the build chamber shall be ensured to meet the forming process conditions.

5.5 Forming process

5.5.1 The forming process is completed with computer assistance.

5.5.2 The main process parameters shall be recorded, and the specific process parameter monitoring and recording shall be determined through negotiation between the supply and demand parties.

5.5.3 If an interruption occurs during the forming process, the interruption status shall be recorded, evaluated, and dealt with based on the evaluation results.

5.5.4 Please refer to Appendix B for the impact of process parameters on the forming quality of parts.

5.6 Powder cleaning

5.6.1 After the forming is completed, the parts should be cooled to ambient temperature or a specific temperature in a protective atmosphere or vacuum environment before powder cleaning.

5.6.2 Anti-static brushes, explosion-proof vacuum cleaners, high-pressure air, etc. can be used for powder cleaning. Parts shall not be damaged during powder cleaning.

6.1 Requirements

6.1.1 Necessary quality inspection shall be carried out before parts are delivered. The supply and demand parties shall negotiate to determine the random inspection method, test items, and technical indicators as delivery and acceptance conditions.

6.1.2 The main characteristics and test methods of parts shall meet but not be limited to the provisions of GB/T 35022.

6.1.3 The mechanical performance evaluation of parts shall comply with the provisions of GB/T 39254.

6.2 Re-inspection

The purchaser can conduct re-inspection according to the requirements of 6.1 according to the agreement between the two parties. If the re-inspection result is unqualified, it will be resolved by negotiation between the supply and demand parties.

A.1 Software information

Record the name, version, and other information of the software involved in the forming process, such as design software, pre-processing software (such as slicing software and support software), control software, and operating system.

A.2 Data information

Record part-forming data, mainly including part model data and data processing information.

A.3 Forming process records

Forming process records include but are not limited to the following information:

a) Feedstock's manufacturer, grade, performance, and batch number;

b) Powder reuse status, including screening, number of reuses, number of batching, batching ratio, etc.;

c) Build platform material and thickness;

d) Type, purity, and flow rate of protective gas;

e) Forming process parameters when laser is used as an energy source, including oxygen content in the build chamber, preheating temperature of the build platform, powder layer thickness, laser power, scanning speed, scanning strategy, spot size, etc.;

f) Forming process parameters when the electron beam is used as an energy source, including electron beam size, scanning speed, scanning strategy, build chamber vacuum degree, powder layer thickness, build platform preheating temperature, etc.;

g) Build chamber temperature after electron beam forming is completed;

h) Post treatment, including all mechanical processing, chemical treatment, heat treatment, etc.; […]