3D printing with metal
Introduction
Selective laser sintering (or SLS) is a rapid prototyping addition printing technique in which a layer of powder, a few tenths of a millimeter in size, is deposited in a vat that has been heated to a temperature slightly below the melting point of the powder. A high-power laser (for example, CO2) then sinters the powder at selected points (causing the particles fuse and solidify).
It is a highly flexible continuous process that allows the conversion of a wide variety of materials. For example, fine iron ore dusts, dusts collected in filters and other iron-containing materials, etc.
It is used for small volumes of parts that need to be functional.
History
Selective laser sintering was developed and patented by Carl Deckard and academic advisor Joe Beaman at the University of Texas at Austin in the mid-1980s, under the auspices of the government agency DARPA. Deckard and Beaman participated in the launch of the start-up company DTM, established to design and build the SLS machines. In 2001, 3D Systems, the largest competitor of DTM and SLS technology, acquired DTM.[2] The most recent patent on Deckard's SLS technology was issued on January 28, 1997 and expired on January 28, 2014.[3].
A similar process was patented without being commercialized by R. F. Housholder in 1979.[4].
The technology
Producing objects using SLS requires the use of a high-power laser (for example, a CO2 laser) to fuse small particles of plastic, metal, ceramic or glass into a desired three-dimensional shape.
The laser selectively fuses material in powder form in a bucket by scanning thin transverse layers that generate the three-dimensional object. The dimensional information of the part to be printed comes from a computer file that has been generated or previously scanned. Once the cross section, or layer, is formed, the powder cup is lowered a distance equivalent to the thickness of the formed layer, and a new layer of base material is added to the surface. The process is thus repeated as many times as layers need to be melted until the three-dimensional object is created.
The finished parts will have a density that depends on the peak power of the laser rather than its duration; SLS equipment uses a pulse laser. The SLS equipment preheats the base powder material in the cuvette to a temperature slightly lower than the melting temperature of said material. In this way it makes the fusion of the material by heating easier.[5].