Selective Laser Sintering: All you Need to Know

Selective Laser Sintering (SLS) is one of additive manufacturing technology. Plastic powder serves as the starting material of SLS Printing process to produce plastic components using the energy input of a laser beam. 

The laser sintering process is divided into 3 recurring steps:

–              Application of the powder layer

–              Adjustment of the temperature

–              Exposure of the current layer

The manufacturing process is conducted inside the printer’s build chamber. The SLS powder is applied onto a thin layer (typically 0.1 mm) above a fabrication platform with temperature set to just below the material’s melting temperature

 

Selective Laser Sintering Process
Selective Laser Sintering Process

The powder requires excellent flowability and good particle size distribution in the range of 10 to 100 µm. This is to ensure that the loose powders are tightly packed together.

The layer of powder is then exposed to a laser beam. The beam melts the powder at correct cross sections of the desired component and fuses it with the layer underneath. Once a layer has been exposed, the printer lowers down the fabrication platform and the next layer of powder is applied.

The powder bed that consists of loose powder & exposed part now functions as a support. The fabrication platform is gradually lowered so that further layers can be added on top. The build chamber then filled additively from top to bottom with speed of approximately 10 mm/h. Typically several hundreds up to thousands small to medium sized parts and components are being fabricated in this step.

The fabricated components are later cooled down with approximately the same time as the fabrication time.

The build chamber container is then removed and carefully emptied in an unpacking station. The excess powder that is not fused and melted during the fabrication step is then reused and recycled for the next printing process. (recycling rates of approximately 10 to 50% are usual for laser sintering and can vary depending on the material used).

Next, the cooled components are cleaned of excess powder using various cleaning method e.g., glass bead blasting. Furthermore, the components can be subjected to further treatment, depending on the surface requirement. 

Finishing of Selective Laser Sintering (SLS) Product
Selective Laser Sintering Components Cleaned & Cleared

Post-processing methods might be required to achieve the component’s desired surface structure. Established methods such as mechanical abrasion, which involves slide grinding with grinding devices (also known as barrel finishing), as well as chemical smoothing are used to smoothen the surface. In addition, colouring by means of infiltration near the surface (penetration depth: approximately 0.3 mm). can improve the look and feel of laser-sintered components.

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