SELECTIVE LASER SINTERING
Selective laser sintering is a power based rapid prototyping process where it involves method of sintering and building up powder particles heated with a carbon dioxide, (〖CO〗_2) laser beam. The sintering process is when a roller spread the fine powder uniformly on the machine bed and it scanned selectively by a laser of power 25-100W such that the surface tension of the grains is overcome and they are sintered together. First powder is pre-heated to temperature slightly below the sintering temperature of the material by infra-red heaters to minimize thermal distortion and to facilitate fusion to the previous layer. The laser beam then scans the cross-sectional area identified for the current slice, thus sintering of the powder takes place. A fresh layer of powder is deposited again across the part bed, and the process is repeated until the final part has been completed. During this process the previous layers of un-sintered powder act as a support for any overhanging features. Once the build is complete, the part, encased in un-sintered powder, is left to cool to …show more content…
Any material can be process in Selective Laser Sintering which are polymers, reinforced and filled polymers, metals and ceramics. However, it is an unavoidable shrinkage happen during sintering process where thermal imbalance occurs in the build chamber. A study has found that there are a few parameters influence the shrinkage happen where laser power and scan length are to be most significant process variables influencing shrinkage in X- direction. Along Y-direction, laser power and beam speed are the significant parameters and along Z-direction beam speed, hatch spacing and part bed temperature are found to be most influenced factors affecting shrinkage. Shrinkage (%) for the specimen in each direction is calculated by using the following