Dr. Dmitri Kopeliovich

Selective Laser Sintering (SLS) is a Rapid Prototyping technique in which a three-dimensional object is fabricated by applying successive layers of powder each of them is sintered and bonded to the preceding layer by local heating generated by a laser beam.

Sintering is a method involving consolidation of powder grains by heating the “green” compact part to a high temperature below the melting point, when the material of the separate particles diffuse to the neighboring powder particles.

Selective Laser Sintering is used for fabrication of parts from polymer, ceramic and metallic powders.

Process of Selective Laser Sintering:

• A thin uniform layer of the powder is spread over the surface of the build chamber. The layer thickness is commonly less than 0.004” (0.1 mm).
• A high power laser beam scan over the layer surface according to Computer-Aided Design (CAD) model of the fabricated part. Scanning is performed by a mirror of the beam deflection system.
• The energy of the laser is focused in a small spot of the layer surface heating the powder to the sintering temperature (a temperature below the melting point but close to it). The powder particles of the layer bind to each other and to the preceding layer due to diffusion of the material.The powder of the layer lying beyond the scanned area remains unsintered. It supports the sintered object in the build chamber.
• The operation of powder spreading followed by laser sintering is repeated until the object building is completed.
• The sintered part is left in the chamber to cool down.
• The sintered model is taken out from the chamber. The excess powder is easily removed by compressed air blasting.

The advantages of Selective Laser Sintering over conventional sintering process:

• Short time between the product concept and fabrication.
• Better flexibility of design. Intrinsic shapes may be fabricated. Several design alternatives may be easily checked.
• More cost effective for manufacturing unique models or small batches of parts.
• The prototypes are stored in digital form and may be reproduced when it is required.
• Functionally graded materials (materials with varying composition and properties over the volume) may be fabricated.

Applications of Selective Laser Sintering:

• Polymers
  • Silicone and epoxy molds;
  • Functional parts made of nylon;
  • Acrylic styrene parts for investment casting;
  • High strength parts made of glass fiber reinforced Thermoplastics (polyamide, polypropylene, polycarbonate, ABS);
  • High strength carbon fiber reinforced polyamide;
  • Artistic objects;
  • Architectural models;
  • Biopolymers (tissue scaffolds);
  • Dental retainers.
• Ceramics
  • Molds for investment casting made from partially stabilized zirconia;
  • Artificial bones and tissue scaffolds;
  • Prostheses.
• Metals
  • Bronze parts;
  • Tools from stainless and tool steels;
  • Structural parts from Titanium alloys (e.g. TiAl6V4);
  • Silicon carbon reinforced aluminum and titanium composites for high strength, low weight, wear resistant parts for automotive and electronic industries.

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• Thermoforming
• Extrusion of polymers
• Injection molding of polymers
• Blow molding
• Compression molding of polymers
• Transfer molding of polymers
• Sintering of metals
• Sintering of ceramics

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