Simply analyze the main influencing factors of additive manufacturing process

Nov 02, 2022

At present, additive manufacturing technology has become a highly concerned technology, which has been vigorously developed in aerospace, automotive, biomedicine and other industries, and has become an important force to promote the transformation and upgrading of traditional manufacturing. Additive manufacturing technology in China has developed rapidly in recent years, and various application service markets are gradually taking shape. Although some achievements have been made in some areas, compared with foreign countries, the technology reserves of the entire industry are insufficient, and the core technologies and patents related to additive manufacturing are controlled by foreign enterprises.

At present, metal materials are still the most widely used in industrial production. It is an important development direction of additive manufacturing technology to use additive manufacturing technology to replace traditional process methods and manufacture metal parts that are difficult to process by traditional processing methods. Different from traditional process methods, additive manufacturing technology puts forward higher requirements on the performance and applicability of materials. However, metal powder materials, as the industrial basis, have become an important factor restricting the rapid development of additive manufacturing industry in China. Although there are many technical methods to realize additive manufacturing, the processing mechanism is basically the same, that is, the materials melt rapidly under the action of high energy heat source. Due to the extremely short action time, the molten metal solidifies rapidly under the cooling effect of the matrix, thus realizing the molding in a specific scanning area. The energy of additive manufacturing products is determined by the properties of heat source, material properties and process parameters. The type of heat source and the way of powder feeding are the most fundamental factors to distinguish various additive manufacturing technologies.

Now, the influence factors of additive manufacturing process are analyzed in detail by ZHONGWEI precision knitting in Qinhuangdao:

1. Heat source

In the field of metal additive manufacturing, the most mature heat sources are lasers and high-energy electron beams. The working principle of electron beam is different from that of laser. The heating mode of electron beam is that high-energy electrons pass through the surface of the target and enter a certain depth from the surface, and then transmit energy to the target atoms, so as to intensify the vibration of the target atoms and convert the kinetic energy of the electrons into heat energy; The laser is heated by absorbing photon energy on the target surface, and the laser does not pass through the target surface. In the process of material manufacturing and processing, the power and scanning speed of the heat source are generally constant, that is, the energy density acting on the material is constant, and the effect of the heat source is directly determined by the absorption performance of the material to the heat source. The absorption of heat source energy by materials is determined by their action mechanism, material surface state and other factors. For the most commonly used laser heat source, the absorption of laser light energy is related to the wavelength, reflectivity of the illuminated material and energy density. During the molding process, the surface state, size and other factors of the material have obvious constraints on the laser. Due to the different mechanism of electron beam, it has better adaptability than laser in the additive manufacturing process.

2. Materials

Powder material is the most commonly used metal additive manufacturing material at present. Metal powder, as the most important link in the metal parts additive manufacturing industry chain, is also the most valuable. Metal powder materials are generally used in the powder metallurgy industry. Powder metallurgy molding refers to the final shaping of the powder under high pressure and high temperature conditions after the powder is preformed. During the whole process, the physical and metallurgical changes of the materials are relatively slow, and the materials have sufficient time for fusion, diffusion and reaction. Due to the limitation of temperature and pressure during powder metallurgy processing, in order to ensure the compactness of the workpiece, it is required to use powder materials to completely fill the forming cavity as much as possible. In view of the technical characteristics of powder metallurgy process, a relatively complete set of powder evaluation methods and standards have been developed, and relatively complete indicators can be used to constant the performance of powder materials, such as particle size, specific surface area, particle size distribution, powder density, flow rate, loose packing density, porosity, etc. For powder metallurgy, the flowability and tap density of powder are important indexes to measure powder materials used in powder metallurgy.

3. Process

When the powder filling method is powder spreading, the heat source acts on the powder preferentially. In order to ensure the full metallurgical combination of the powder and the formed area, it is necessary to ensure that the depth and size of the molten pool in the processing process are within a reasonable range. When the synchronous powder feeding mode is adopted, no matter the coaxial powder feeding mode or the lateral powder feeding mode, the effect of the heat source on the material can be divided into two parts: the effect on the formed area and the effect on the powder material. After the powder is heated to a certain temperature by the heat source during movement, it is driven into the formed area under the action of its own kinetic energy. The whole forming process is equivalent to the process of relatively high-energy powder materials bombarding the fusion area. This method is more conducive to improving the density of products than the powder spreading method.

The additive manufacturing process is obviously different from the powder metallurgy process. The metallurgical change of powder materials under the effect of heat source is extremely fast. During the forming process, the powder materials directly act on the heat source. The powder materials have no mold constraints and external permanent pressure. It is generally believed that powder materials with diameter less than 1mm are suitable for additive manufacturing, and the particle size is 50 μ The powder material of m or so has good molding performance. Compared with the powder metallurgy industry, at present, there is no mature evaluation method or standard to determine the applicability of powder materials and additive manufacturing processes in China, and the related evaluation methods and indicators of powder for additive manufacturing need to be further studied and considered.

If you want to know more about metal powder metallurgy, please consult Qinhuangdao Zhongwei Precision.