Selective Laser Sintering (SLS)
Author: Date: 2021-3-11 10:49:43
Selective laser sintering,as the name implies,uses a liquid-phase sintering mechanism. The powder material is partially melted during the forming process,and the powder particles retain their solid-phase core and undergo subsequent solid-phase particle rearrangement and liquid-phase solidification. Bonding realizes powder densification.
SLS technology principle and characteristics
The entire process device is composed of a powder cylinder and a forming cylinder. The working powder cylinder piston (powder feeding piston) rises,and the powder spreading roller spreads the powder evenly on the forming cylinder piston (working piston),and the computer controls it according to the prototype's slice model. The two-dimensional scanning trajectory of the laser beam selectively sinters the solid powder material to form a layer of the part. After one layer is completed,the working piston is lowered by one layer thickness,the powder spreading system is spread with new powder,and the laser beam is controlled to scan and sinter the new layer. This cycle repeats,layer by layer,until the three-dimensional part is formed.
The SLS process uses a semi-solid liquid phase sintering mechanism. The powder is not completely melted. Although it can reduce the thermal stress accumulated by the forming material to a certain extent,the forming part contains unmelted solid particles,which directly leads to high porosity and density. Process defects such as low tensile strength,poor tensile strength,and high surface roughness. In the SLS semi-solid forming system,the viscosity of the solid-liquid mixed system is usually high,resulting in poor fluidity of the molten material,and the metallurgical defects unique to the SLS rapid prototyping process will appear. "Spheroidization" effect. The spheroidization will not only increase the surface roughness of the formed part,but also make it difficult for the powder spreading device to spread the subsequent powder layer evenly on the surface of the sintered layer,thus hindering the smooth development of the SLS process.
Due to the low strength of sintered parts,post-processing is required to achieve higher strength,and the manufactured three-dimensional parts generally have problems such as low strength,low precision and poor surface quality. In the early stage of SLS,compared with other mature rapid prototyping methods,selective laser sintering has the advantages of a wide selection of molding materials and a relatively simple molding process (without support). However,because the energy source in the molding process is laser,the application of lasers makes the cost of molding equipment higher. With the rapid progress of laser rapid prototyping equipment after 2000 (indicated by the use of advanced high-energy fiber lasers and the improvement of powder spreading accuracy) Etc.),the metallurgical mechanism in which the powder is completely melted is used for rapid laser forming of metal components. Selective laser sintering technology (SLS) has been replaced by similar more advanced technology.