Introduction to the process
SLS (Laser) is a rapid forming process:
Chinese translation: selective laser sintering of powder materials/laser selection sintering/powder sintering
In 1986, C., a graduate student at Texas University in the United States, proposed the idea of Laser Sinte ring (SLS), which was successfully developed in 1989, and later established DTM company, and developed a commercial forming machine based on SLS in 1992;
DTM has been acquired by 3D.
The SLS process is formed using powdered materials. Spread the powder of material on the upper surface of the formed parts and scrape them flat;
The part cross-section is scanned on the newly laid new layer with a high-intensity CO2 laser; the material powder is sintered together under high-intensity laser irradiation to obtain the cross-section of the part and is connected to the formed part below;
When the cross-section of one layer is sintered, a new layer of powder material is laid and the lower cross-section is selected.
Process Features
⑴ A variety of materials can be used: any shape can be made from materials or various adhesive-containing coating particles using any powder with reduced viscosity upon heating; in particular, metal parts can be made. This makes the SLS process attractive;
⑵ The manufacturing process is relatively simple: it can directly produce prototypes, molds, three-dimensional co-construction or components and tools of complex shapes, which can widely adapt to design and changes;
⑶ High accuracy: depends on the type of materials used and particle size, the geometry and complexity of the product. Generally, it can be expressed when the details of the part are greater than 0.5mm. Able to achieve tolerance of ± (0.05-2.5) mm within the overall scope of co-construction. When the powder particle size is less than 0.1mm, the prototype accuracy after forming can reach ± 1%.
⑷ Material utilization is high, cheap, and low cost;
⑸ Warpage deformation is smaller than that of SLA technology, and it is possible to design and manufacture fine and strip-like parts;
⑹ Parts formed using high-temperature sintered materials have good physical characteristics such as strength and hardness;
⑺ Difficulty 1: The surface of the part is rough and has large particles, and the surface needs to be polished manually;
⑻ Difficulty 2: When sintering engineering plastic materials, it is necessary to maintain the balance of the temperature field in the working area, and the temperature needs to be controlled between 150℃ and 200℃.
SLS is the selective laser sintering molding method, its principle is:
1) Store powder particles in the feed bin on the left. When printing, the feed bin lifts upwards. The powder higher than the printing plane is pushed onto the printing plate with a powder laying drum to form a very thin powder layer plane;
2) At this time, the laser beam scanning system will selectively scan the powder layer according to the slice CAD path. The scanned powder particles will be sintered together due to the high temperature of the laser focus, and a solid sheet with a certain thickness will be generated. The unscanned area will still remain in powder form;
3) After the first layer is sintered, the printing platform drops according to the cutting height, and the horizontal drum flattens the powder again, and then the sintering of the new layer is started. At this time, the layers are also sintered together at the same time;
4) Repeat this until all levels are sintered. Recycle unsintered powder and remove the printed solid model.
Principles and advantages and disadvantages of SLS process
The advantages of SLS process are very obvious when compared with other processes:
1) Extensive molding materials. Generally speaking, any powder material that can form interatomic bonding after heating can be used as its molding material;
2) Any complex structure can be printed, including hollow structures, hollow structures, etc. The process has nothing to do with the complexity of the parts, and the strength of the parts is high;
3) The material utilization rate is high, the unsintered powder can be reused, and the material is wasteful;
4) No support structure is required, loose powder plays a supporting role, reducing the difficulty of processing the model in the early stage of printing;
5) The SLS process can process standard plastics with good mechanical properties;
6) The types of processable materials continue to increase, and the price advantage is obvious in small batch production.
The only drawback is that compared with the corresponding injection molded parts, the performance of SLS process products is not completely consistent, especially the product surface is relatively rough.
