Since its introduction, 3D printing technology has achieved rapid development and has shown great application value in many fields. In particular, its application in the field of metal forming has created a new development direction for the manufacturing industry and effectively driven the development of the manufacturing industry. Based on the analysis of the application of 3D printing technology in the field of metal forming, this paper summarizes the existing problems and puts forward future prospects.
3D printing technology has developed rapidly in the manufacturing industry and many other industries due to its strong application ability and strong replicability, and has become an important technical support for the manufacturing industry, affecting the future direction of the industry. In the field of metal forming manufacturing, 3D printing technology has also been widely used and has shown great potential. It can be formed in a short time, shorten the manufacturing cycle, and drive the metal forming manufacturing industry to develop in a faster and better direction.
3D printing technology requires the use of metals, ceramics and other materials to complete the manufacture of objects during the forming process. For metal printing, most of the printed parts are metal parts, the structure of the parts is relatively complex, and the volume is small. It is difficult for manual manufacturing of these parts. With the support of metal 3D printing technology, some technical problems can be solved well, which also makes the application of this technology in different industries more likely. The application in the field of metal forming has greatly promoted the development of manufacturing industry and promoted the progress of forming technology.
1 Development of 3D printing technology for metal parts
1.1 Laser engineering net forming technology (LENS)
This technology was first proposed by Sandia National Laboratory in the United States. For metal materials, the melting point itself is very high, and some problems are easy to occur during the processing. The development of laser engineering net forming technology can use metal powder raw materials to complete printing, and in a quantitative way, let the printing equipment know the specific printing quantity and printing structure to achieve rapid part forming. From the specific equipment composition, it is mainly composed of three parts: coaxial powder feeder, powder feeder head and protective gas path. The specific use process is: first, according to the actual needs of the project, use the powder feeder to hand over the metal powder to the processing equipment, and then determine the specific powder flow rate according to the stepper motor. This value can also be adjusted by the background system. In the process of transferring from the powder feeder to the powder head, the metal powder is transported inside the pipe by its own weight and evenly ejected to complete the segmentation. Finally, the powder will be melted and accumulated at the intersection of the laser focus and the nozzle. In this process, by protecting the gas, the metal dust and the melted material can be effectively isolated, thereby avoiding the oxidation of the metal during the printing process.
1.2 Selective Laser Melting Technology (SLM)
In terms of metal forming requirements, the manufacturing of metal parts has very high requirements for precision. It is necessary to accurately control the melting area during the melting printing process, and control the melting speed and time, so as to ensure the accurate printing of metal parts. Selective laser melting technology can handle the above problems well. Specifically, it is mainly for the staff to use specific software to build the model, keep the parameters of the model consistent with the parameters of the parts to be made, and these data will be effectively sliced and layered before entering the equipment to start manufacturing. At the same time, the printing equipment will also analyze the material, refer to the different types of materials and models, and complete the addition of scanning lines according to specific characteristics. The existence of these scan lines can better support the subsequent laser beam selection operation and ensure the accuracy of the data. In the specific operation process, the equipment will first lay the metal powder flat, and then melt it layer by layer according to the scan lines designed by the software, and use this repeated operation to build the required material. In this process, due to the presence of inert gas, there is no need to consider that the metal will combine with the air after the temperature changes and produce adverse reactions.
1.3 Electron beam selective melting technology (EBSM)
Electron beam selective melting technology mainly uses high-energy electron beams as the heat source for processing. It uses the characteristics of high-energy electron beams themselves to build a relatively perfect vacuum environment. There is no need to isolate the materials separately to ensure that the materials are not in contact with the external air and avoid quality changes. Currently, this technology is mainly divided into two types: the first type is similar to the laser selective melting technology. First, the metal powder needs to be flattened and then melted. The difference is that under the attack of the electron beam, the metal powder can be quickly melted. After the melting is completed, the metal material is re-flattened, and the material is sintered according to the data content, and then piled up to complete the construction of the entire part model; the second type is that the selected material is a relatively thin metal wire, and the metal wire is quickly melted by the electron beam. In this process, the device that generates the electron beam is not moved, but a special workbench is used to complete the orderly movement of the metal material through continuous comparison to achieve the final melting.
2 Application research of 3D metal printing technology
With the passage of time, related technologies are constantly optimized, but they are not fully mature. 3D metal printing technology is still in the development stage. At this stage, many new technologies have also emerged, and the application characteristics and application scope of different technologies are also different. Therefore, the following article combines the specific technical content introduced above, starting from the application scope and application situation, and conducts a more in-depth analysis and research on these technologies.
2.1 Laser Engineering Net Forming Technology
This technology effectively combines laser sintering technology and laser cladding forming technology, and can be effectively applied to a variety of metal materials. It has strong applicability and is also commonly used in metal parts manufacturing. Specifically, according to the different types of metal powders, different waiting times, and different powers are used to melt the metal powders. After the melting is completed, these materials can be printed according to the predetermined trajectory, and finally metal parts with good performance and generally do not need to be processed again are obtained. It can well meet the printing of metal parts with high precision and basically guarantee the expected functions of metal materials. Since the concept was proposed, it has been highly valued by the American industrial community, and it is proposed that this technology is the most creative industrial technology in today’s era. Later, with the gradual deepening of research and optimization and improvement, it was found in austenitic stainless steel specimens that when the number of processing layers increases, the hardness index will decrease significantly. In addition, foreign research institutions have also applied this technology to the porous and functional gradient structure manufacturing of load-bearing implants, through the research of alloy preparation with high degree of integration with the human body. Through research, it was found that this processing technology has a high usability and a long service life when processing metal parts implanted in the human body, and the porosity is basically over 70%. my country has also made good progress in the application research of this technology, mainly in the manufacture of network iron-based metal glass components, and effectively improved the hardness of the glass.
2.2 Laser Selective Melting Technology
According to the introduction in the previous article, compared with these technologies, laser selective melting technology is a relatively simple one, which can realize the rapid forming of metal powder. When making metal parts, the selected metal materials are generally nickel-based metals, precious metals or stainless steel, etc., which are composed of a single metal powder. With the support of a certain energy density laser, the metal powder is completely melted and solidified into a predetermined shape through preset parameters. The technology used to produce this component mainly considers its density requirements, and its precision is high. Therefore, it can also be used in aerospace, jewelry processing, microelectronics and other industries, and has great development prospects. However, from the actual situation, due to the different properties of different materials, different environments, and different equipment, the manufactured parts cannot guarantee the perfection of performance. Various problems are prone to occur during the processing, which ultimately lead to different defects in the parts. In response to these problems, relevant research institutions abroad have also discussed and made some suggestions, and are constantly optimizing and improving the process. By considering the laser power, scanning spacing and speed involved in the technology, as well as the thickness of the powder on the base plate, and by flexibly adjusting different parameters, it was found that these factors would not have much impact on the manufacturing of the final parts in the process of continuous debugging. Then starting from the problems existing in the manufacturing of metal parts, based on a detailed analysis of the defects, it was found that most of the defects showed spheroidization and warping deformation, which was basically caused by incomplete melting of the metal powder. Under the influence of surface tension, the metal liquid would flip into a spherical shape before it was completely melted, and these defects eventually appeared. Then through continuous summary and continuous adjustment, it was found that to avoid this situation, the input power of the laser can be increased during the melting of the metal powder, but the power cannot be adjusted too high, otherwise deformation in the plastic stage will also occur easily. However, there is no specific solution for what standard the power should be adjusted to and how it should be maintained at this level. In the process of experiment, we can only use the finite element method to conduct continuous testing. However, objectively speaking, since the potential of this technology is huge and it is predicted that it can have outstanding results in aerospace, microelectronic machinery and biological implants, it has also received high attention in recent years and the academic community is also continuously studying it.
2.3 Electron beam selective melting technology
This technology was developed in the mid-1990s. It is basically the same as the forming principle of traditional technology, but the heat source used is different. Other technologies use laser energy, while this technology uses a unique energy source. From the perspective of energy utilization, the process used can effectively enhance the utilization of energy, and it is non-reflective and easy to focus. After combining with 3D printing technology, it can ensure the rapid manufacturing of parts, effectively save manufacturing time, and the precision of the manufactured parts is also very high, which can effectively meet the needs, and therefore this technology has received widespread attention. By sorting out the existing research data, it can be seen that in the process of using this process, the acceleration voltage of the electron beam and the fast reading of the scanning line can ensure the rapidity of scanning, and the linear relationship between these elements is also obvious. At the same time, by sorting out these data, we can also understand that the quality of metal parts can be well guaranteed by adjusting the scanning line and the overlap rate. Based on these data, the hardness tensile test of the test piece was carried out, and it was found that during the forming process of the parts, the loss of AI elements was obvious, but it did not have much impact on the hardness and volume height of the parts, and the hardness level was higher, indicating that this technology also has certain advantages in ensuring the quality of parts.
3 Prospects of metal 3D printing technology
The development of traditional human processing skills has gone through thousands of years, and 3D printing technology has only been less than fifty years since its creation. The emergence of various technologies also indicates that in the future, there will be more efficient, richer performance and more cost-effective metal 3D printing technologies and materials. For my country, we should strengthen research in this field, strengthen the investment of talents and resources, and implement metal 3D printing technology innovation. From the perspective of specific R&D paths, there are mainly the following aspects: First, implement the mutual integration of metal 3D printing technology and traditional metal manufacturing technology, and pay attention to the research and development and innovation of removal processing technology to achieve effective combination of different technologies; second, implement the integration of metal 3D printing technology and heat treatment process, use instant heat treatment to effectively change the performance of the product after printing, and ensure the quality of the product; third, implement the integration of metal 3D printing technology and support removal technology, reduce support design, so as to ensure that the overall adaptability of the technology is higher; fourth, explore multi-nozzle technology, and lay the foundation for the popularization of metal 3D printing technology by further improving production efficiency.
