At present, many major achievements have been made in RP molding systems, SLS molding machines, metal powder research, sintering theory, and scanning paths in China.
The principle of SLS 3D printing:
1) The plastic powder is in the feeding bin on the left, and the lifting platform of the powder feeding bin rises up during printing, and the powder is pushed onto the printing plate by the powder spreading roller to form a very thin powder layer plane;
2) Selective scanning is performed on the powder layer according to the CAD path of the slice, and sintered together due to the high temperature of the laser focus to generate a solid slice with a certain thickness;
3) After one layer of sintering is completed, the printing platform descends according to the cutting height, and the horizontal roller spreads the powder again, and then starts a new layer of sintering;
4) Repeat this until all layers are sintered. The printed solid model can be taken out by recycling the unsintered powder.
Post-processing
After taking it out of the molding room, use brushes and special tools to remove the excess powder on the workpiece. After further cleaning and polishing, further processing is required for the prototype material.
Advantages and disadvantages of the SLS process
(1) Advantages of the SLS process
1) Diversity of molding materials and low price. It is the most notable feature of SLS. Theoretically, all materials that can form atomic connections between powders after laser heating can be used as SLS molding materials. At present, the commercialized materials mainly include plastic powder, wax powder, coated metal powder, ceramic powder coated with a binder on the surface, coated sand, etc.
2) There are almost no requirements for the shape of the workpiece. Since the powder in the lower layer naturally becomes the support of the upper layer, SLS is self-supporting and can produce any complex shape, which is not available in many RP technologies. Forming is not limited by the inability of tools to reach certain surfaces in conventional machining.
3) The material utilization rate is high. The unsintered powder can be reused.
4) The parts have good mechanical properties. The finished product can be directly used for functional testing or small batch use.
5) Realize the integration of design and manufacture. The supporting software can automatically convert CAD data into layered STL data, automatically generate NC codes according to layer information, and drive the forming machine to complete layer-by-layer processing and accumulation of materials without human intervention.
(2) Disadvantages of the SLS process
1) The equipment cost is high.
2) The interior of the part is loose and porous, the surface roughness is large, and the mechanical properties are not high.
3) The quality of the product is greatly affected by the powder, and it is not easy to improve.
4) The maximum size of manufacturable parts is limited.
5) The molding process consumes a lot of energy, and the post-processing process is complicated.
SLS application example
SLS technology has been successfully applied in many industries such as automobile, shipbuilding, aerospace, aviation, communication, micro-electromechanical system, construction, medical treatment, archaeology, etc. It has injected new creativity into many traditional manufacturing industries, and also brought the breath of informatization. In summary, the SLS process can be applied to the following occasions:
1) Rapid prototyping. The SLS process can quickly manufacture the prototype of the designed parts, and evaluate and correct the products in time to improve the design quality; it can enable customers to obtain intuitive part models; it can manufacture complex models for teaching and testing.
2) Preparation and research and development of new materials. Using the SLS process, some new types of particles can be developed to strengthen composite materials and cemented carbide.
3) Manufacturing and processing of small batches and special parts. In the field of manufacturing, the production of small batches and special parts is often encountered. Such parts have a long processing cycle and high cost, and for some parts with complex shapes, they cannot even be manufactured. The use of SLS technology can economically realize the manufacture of small batches and complex shapes.
4) Rapid tooling and tooling manufacturing. The parts manufactured by SLS can be directly used as molds, such as investment casting, sand casting, injection molding, high-precision metal models with complex shapes, etc.; molded parts can also be used as functional parts after post-processing.
5) Application in reverse engineering. The SLS process can re-create the prototype CAD volume according to the existing part prototype by using various digital and CAD technologies without design drawings or incomplete drawings and without CAD models.
6) Application in medicine. Parts sintered by the SLS process can be used for artificial engineering because of their high porosity. According to foreign clinical research on artificial bone prepared by SLS technology, the biocompatibility of artificial bone is good.
The development of SIS technology will have a positive impact on equipment research and development and application, research on new technology and new materials, and will greatly promote the development of the manufacturing industry towards environmental protection, energy saving, and high efficiency.
JR has made a great contribution to the SLS process, providing customers with rapid prototypes, rapid prototypes, final parts, etc. It mainly includes automobiles, consumption, construction, shipbuilding, aerospace, and other fields.