1, Porosity problem and its solutions
Porosity is one of the common problems in metal 3D printed parts, mainly manifested by the presence of small holes and cavities inside the parts. These pores will reduce the density of the parts, thereby affecting their mechanical properties such as strength, hardness, and toughness. The formation of pores is mainly due to issues with powder production technology or the 3D printing process itself. For example, pores in powder materials may be formed during gas atomization, while pores during printing may result in the metal not melting properly due to insufficient energy, or excessive laser energy may cause droplets of melted material to splash.
To reduce porosity, the following measures can be taken:
Optimize powder materials: Choose high-quality metal powders to ensure low pore content in the powder. At the same time, by adjusting the particle size distribution of the powder, the flowability and bulk density of the powder are improved, thereby reducing the amount of pores in the parts.
Adjust printing parameters: For specific materials and tasks, adjust printing parameters such as laser power, spot size, and shape to optimize the melting process and reduce pore formation. For example, in SLM technology, powder splashing can be reduced by adjusting the shape of the light spot; In the EBM process, the problem of powder splashing can be improved by rapidly scanning and preheating the powder bed with an electron beam.
Post processing: Adopting hot isostatic pressing and other post-processing methods to further reduce porosity and improve density in the parts.
2, Density problem and its solutions
Density is another important indicator of metal 3D printed parts, which directly affects the mechanical properties and reliability of the parts. Powder bed melting (SLM, EBM) technology can produce components with a density of 98% or higher, which is crucial for the application of automotive parts. However, due to various factors such as powder quality, printing parameters, etc., the actual density of the parts may be lower than the expected value.
To increase the density of parts, the following measures can be taken:
Optimize powder materials: Choose powder materials with spherical particles, as spherical particles can achieve maximum relative density. At the same time, ensure that the particle size distribution of the powder is uniform to improve the bulk density and flowability of the powder.
Adjusting printing parameters: By optimizing printing parameters such as laser power, scanning speed, layer thickness, etc., the melting process can be improved and the density of the parts can be increased.
Post processing: Fill the remaining gaps in the parts using infiltration method to further increase density.
3, Residual stress problem and its solutions
Residual stress is another common issue in metal 3D printed parts, mainly caused by changes in temperature and expansion and contraction processes. Residual stress may cause defects such as deformation and cracking of parts, seriously affecting their performance and reliability.
To reduce residual stress, the following measures can be taken:
Optimize printing parameters: Optimize parameters such as heat input and layer thickness through predictive modeling to construct components with low residual stress.
Add support structure: Add support structure during the printing process to improve the bonding force between the part and the printing bed, and reduce the occurrence of residual stress.
Preheat the printing bed: Preheat the printing bed and construction materials before printing begins to reduce temperature gradients and thus reduce residual stresses.
4, Cracking and warping problems and their solutions
Cracking and warping are common structural problems in metal 3D printed parts, mainly caused by residual stress. These issues typically occur during the cooling stage of molten metal after printing, which can cause shrinkage and result in curled and deformed edges of the parts. In extreme cases, stress may exceed the strength of the component, leading to cracking.
To prevent cracking and warping, the following measures can be taken:
Preheating the printing bed: By preheating the printing bed, the temperature gradient is reduced and residual stress is lowered.
Optimize support structure: Design a reasonable support structure to improve the bonding force between the parts and the printing bed, and prevent warping.
Post heat treatment: Using post heat treatment methods such as hot isostatic pressing to help repair small cracks and further improve the strength and toughness of the parts.
5, Surface roughness problem and its solutions
The surface roughness of metal 3D printed parts is an important factor affecting their appearance quality and application performance. Surface roughness is directly related to layer thickness, with thicker layers resulting in a rougher surface. In addition, improper melting of powder may also lead to surface roughness.
To improve surface roughness, the following measures can be taken:
Optimize printing parameters: Reduce surface roughness by reducing layer thickness and increasing laser power. However, it should be noted that using finer layers to produce parts will significantly increase the construction time.
Post processing: Using post-processing methods such as machining, grinding, or polishing to further improve the surface smoothness of the parts.
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