Selective Laser Sintering (SLS) is a 3D printing technology that belongs to the powder bed fusion process family that can produce high-precision and durable parts that can be used directly for end use, small batch production or prototype parts. Selective laser sintering technology is at the heart of the growing trend towards mass custom manufacturing and functional prototyping.
This article covers SLS, including definitions, advantages and disadvantages, process steps, comparisons and materials.
What is selective laser sintering?
SLS is an abbreviation for Selective Laser Sintering, a popular 3D printing solution for rapid prototyping and an additive manufacturing process. In SLS 3D printing, the laser selectively sinters particles of polymer powder, fusing them together and building parts layer by layer. The material used in SLS is a granular thermoplastic polymer.
What are the advantages and disadvantages of SLS?
Advantages of the SLS process
1) Diverse molding materials and low price. This is the most significant feature of SLS.
2) The manufacturing process is simple. There are almost no requirements for the shape of the part. Since the powder of the lower layer naturally becomes the support of the upper layer, SLS is self-supporting and can manufacture arbitrarily complex shapes, which is not available in many RP technologies. Forming is not limited by the fact that the tool cannot reach certain profiles in conventional machining.
3) High material utilization. Unsintered powder can be reused.
4) The parts have good mechanical properties. The finished product can be used directly for functional testing or in small batches.
5) Realize the integration of design and manufacturing. The supporting software can automatically convert CAD data into hierarchical STL data, automatically generate CNC code according to the level information, and drive the molding machine to complete the layer-by-layer processing and accumulation of materials without human intervention.
6) High precision. Generally, it can achieve a tolerance of (0.05-2.5) mm in the overall range of the workpiece.
Disadvantages of the SLS process
1) The equipment is costly.
2) The internal parts are loose and porous, the surface roughness is large, and the mechanical properties are not high.
3) The quality of parts is greatly affected by the powder, and it is not easy to improve.
4) The maximum size of the parts that can be manufactured is limited.
5) The molding process consumes a lot of energy and the post-processing process is complicated.
How does SLS process work?
1. Parameter selection
Delamination parameters: delamination thickness, part processing direction, scanning spacing, etc. Forming sintering parameters include scanning speed, laser power, powder type, spreading thickness…
2. Prototyping
● Using powder to spread a layer of powder material on the surface of the molded part.
● Heating to a certain temperature just below the powder sintering point.
● The control system controls the laser beam according to the cross-sectional contour of the layer to scan on the powder layer, so that the temperature of the powder rises to the melting point, sintering and bonding with the formed part below.
● After one layer is completed, the table is reduced by one layer of thickness, and the spreading roller spreads a layer of uniform dense powder on top and sinters a new layer of cross-sections until the entire model is completed.
3. Post-processing
After being removed from the molding chamber, excess powder is removed from the part with a brush and special tools, and after further cleaning and sanding, the prototype material is further processed.
What’s the application of SLS?
SLS process has been successfully applied to many industries such as automotive, shipbuilding, aerospace, aviation, communications, MEMS, construction, medical, archaeology and many other industries, injecting new creativity into many traditional manufacturing industries and bringing the breath of informatization. In summary, the SLS process can be used in the following applications:
1) Rapid prototyping.
2) Preparation and research and development of new materials.
3) Manufacturing and processing of small batches and special parts.
4) Rapid tooling and tool manufacturing.
5) Application in reverse engineering.
6) Application in medicine.
What is the difference between SLS and SLA?
● Durability and strength: In general, SLS is made more durable.
● Surface finish: SLA will manufacture parts with a high-quality, smoother surface finish.
● Resolution: SLAs provide higher resolution compared to SLS.
● Part Size: SLA printers have a larger build range than SLS machines.
●Heat and chemical resistance: SLS materials will have better overall heat and chemical resistance than SLA parts.
What materials are used for SLS?
1. Plastic powder SLS
Features: Nylon, polystyrene, polycarbonate, etc. can be used as raw materials for plastic powder. Generally, laser sintering is used directly without subsequent treatment
2. Metal powder SLS
Features: The raw materials are various metal powders. According to different sintering processes, it can be divided into direct method, indirect method and double component method. Due to the high temperature of the metal powder SLS, in order to prevent oxidation of the metal, it is necessary to put the gold wish into a container that is the general protection gas (nitrogen, argon, hydrogen, etc.) during sintering. This process, also known as laser selective melting molding method, that is, SLM process, can be regarded as an important branch of SLS process
3. Ceramic powder SLS
Features: Ceramic powder should be added to the powder when sintering. There are three types of binders: inorganic binders, organic binders and metal binders.
Conclusion
SLS parts can be designed with part integration in mind, eliminating the need for assembly processes common in traditional manufacturing. Engineers can now design production geometries that are not possible with other technologies, saving time and money.
In recent years, the process of computer chips has reached the nanometer level, and shrinking chips is almost impossible to achieve. As a result, in the field of circuit carrier boards, a new process technology route has been produced – the use of laser plastic powder SLS 3D printers to help PCB circuit board prototype production. We look forward the fierce collision between SLS and PCB in electronics manufacturing industries in the future.
