Common processes: DMLS (direct metal laser sintering), SLM (selective laser melting) and EBM (electron beam melting)
Description: metal parts produced by PBF melting technology can reduce residual stress and internal defects, making it an ideal choice for harsh applications in aerospace and automotive industries.
1.Direct metal laser sintering (DMLS): it can be used to build almost any metal alloy object. Direct metal laser sintering spreads a very thin layer of metal powder on the surface to be printed. The laser passes slowly and steadily through the surface to sinter the powder, and the inner particles of the metal fuse together, even if they are not heated to a fully molten state. An additional layer of powder is then applied and sintered to “print” one cross-section of the object at a time. After printing, the object will cool slowly, and the excess powder can be recycled from the construction room and recycled. The main advantage of DMLS is that it produces objects without residual stress and internal defects, which is very important for metal parts under high stress (such as aerospace or automotive parts), and the main disadvantage is very expensive.
2.Selective laser melting (SLM): use high-power laser to completely melt each layer of metal powder, not just sintering, so that the printed object is very dense and solid. At present, this process can only be used for certain metals, such as stainless steel, tool steel, titanium, cobalt chromium alloy and aluminum. The high temperature gradient during SLM manufacturing will also lead to stress and dislocation in the final product, which will damage the physical properties.
3.Electron beam melting (EBM): very similar to selective laser melting, it can produce dense metal structure. The difference between the two technologies is that EBM uses an electron beam instead of a laser to melt metal powder. At present, electron beam melting can only be used for a limited number of metals. Although cobalt chromium alloy can also be used, titanium alloy is still the main raw material of this process. This technology is mainly used to manufacture parts for the aerospace industry.
Technical advantages: it can manufacture almost any geometry with high precision. A wide range of metals are used, including the lightest titanium alloy and the strongest nickel superalloy, which are difficult to process by traditional manufacturing technology. Mechanical properties can be comparable to forged metal, and can be machined, coated and treated like traditional metal parts.
Technical disadvantages: high material, machinery and operation costs. The parts must be connected to the construction board through a support structure (to prevent warpage), which will generate waste and require manual post-treatment removal. The construction size is limited, and the metal powder treatment is dangerous, which requires strict process control.