Which rapid prototyping process uses a moving laser beam to sinter heat-fusible powders one layer at a time?

• A. Selective Laser Sintering (SLS)
• B. Stereolithography (SLA)
• C. Direct metal laser sintering (DMLS)
• D. Fusion deposition modelling (FDM)

Answer: (A)

The concept being tested is fusing powder with a laser to build a part layer by layer. In this method, a laser scans across the surface of a bed of heat-fusible powder, fusing only the particles that form the cross-section of the object. After each layer is completed, the build platform lowers by a precise amount and a new layer of powder is spread over the bed, then the laser repeats the pattern for the next layer. The surrounding unfused powder acts as support, so no extra supports are needed. This behavior—moving a laser to selectively fuse powder in successive layers—fits Selective Laser Sintering precisely, making it the best match. Stereolithography uses a liquid resin cured by light; Direct Metal Laser Sintering is a metal-powder variant of laser sintering; and FDM deposits melted plastic rather than sintering a powder bed.