The Laser Sintering Process

Laser Sintering operates in a similar way to Stereolithography, both being layer-additive processes. Stereolithography's photosensitive resin is replaced by a fine heat fusible powder such as wax or thermoplastic. The powder is stored in powder feed cartridges at either end of the build envelope.

The powder is pushed out from the cartridge by a piston and a roller spreads an even layer over the build envelope. A high powered, typically 50 watt, CO2 laser draws each slice of the CAD model on the surface of the powder, locally melting and fusing it together. The build envelope is then lowered by one slice thickness, and the process repeated until the model is complete. The process is illustrated below.

A certain proportion of the laser energy is transformed into heat, this depends upon the powder material and its characteristics. Laser output can be minimized through maintaining the powder at a temperature just below its melting point.

The process is maintained and conducted within the chamber of the manufacturing machine, in an inert nitrogen environment. This is necessary to avoid oxidation of the bonding surfaces and the potential combustion of powder particles.

The finished part is embedded in a cake of surrounding powder which supports it during the manufacturing process. The powder cake serves a useful purpose as it retains heat, and avoids the rapid cooling which causes internal stresses. At the end of the build, the platform on which the part rests is raised and the excess powder is removed.