What is Selective Laser Sintering – Advantages and Disadvantages

Introduction to Selective Laser Sintering : 

Additive manufacturing, or 3D printing, is the process of turning digital designs into three-dimensional objects. It is a convenient and affordable way to make prototypes as well as finished products, making it popular with businesses, hobbyists and inventors.

One of the technologies used by today’s 3D printers is called selective laser sintering (SLS). During SLS, tiny particles of plastic, ceramic or glass are fused together by heat from a high-power laser to form a solid, three-dimensional object.

The SLS process was developed and patented in the 1980s by Carl Deckard — then an undergraduate student at the University of Texas — and his mechanical engineering professor, Joe Beaman.

Selective laser sintering (SLS) is an additive manufacturing (AM) technique that uses a laser as the power source to sinter powdered material (typically metal), aiming the laser automatically at points in space defined by a 3D model, binding the material together to create a solid structure. It is similar to direct metal laser sintering (DMLS); the two are instantiations of the same concept but differ in technical details. Selective laser melting (SLM) uses a comparable concept, but in SLM the material is fully melted rather than sintered, allowing different properties (crystal structure, porosity, and so on). SLS (as well as the other mentioned AM techniques) is a relatively new technology that so far has mainly been used for rapid prototyping and for low-volume production of component parts. Production roles are expanding as the commercialization of AM technology improves.

Working of SLS – Selective Laser Sintering 

In this method, a thin layer of powder is applied using a roller. The SLS uses a laser beam to selectively fuse powdered materials, such as nylon, elastomers and metals into a solid object as shown in the Fig. 

selective laser sintering process
selective laser sintering process

The CO2 laser is often used to sinter successive layers of powder instead of liquid resin. Parts are built upon a platform which sits just below the surface in a bin of the heat-fusible powder. A beam of laser then traces the pattern on the very first layer thereby sintering it together. The platform is further lowered by the height of the second layer and powder is again applied. This process is continued until the part is completed. The excess amount of powder at each layer helps to support the part during its build-up.

Advantages of SLS

  • A distinct advantage of the SLS process is that because it is fully self-supporting, it allows for parts to be built within other parts in a process called nesting – with highly complex geometry that simply could not be constructed any other way.
  • Parts possess high strength and stiffness
  • Good chemical resistance
  • Various finishing possibilities (e.g., metallization, stove enameling, vibratory grinding, tub coloring, bonding, powder, coating, flocking)
  • Bio compatible according to EN ISO 10993-1 and USP/level VI/121 °C
  • Complex parts with interior components, channels, can be built without trapping the material inside and altering the surface from support removal.
  • Fastest additive manufacturing process for printing functional, durable, prototypes or end user parts.
  • Vast variety of materials and characteristics of Strength, durability, and functionality, SLS offers Nylon based materials as a solution depending on the application.
  • Due to the excellent mechanical properties the material is often used to substitute typical injection molding plastics.

Disadvantages
SLS printed parts have a porous surface. This can be sealed by applying a coating such as cyanoacrylate.

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