Stereolithography (SLA) or Selective Laser Sintering (SLS)

Il processo stereolitografico (SLA è l’abbreviazione di StereoLitographic Apparatus) coinvolge quattro differenti tecnologie: laser, ottica, chimica dei fotopolimeri e software, ed è il primo e più importante sistema di RP commercialmente diffuso. Il processo è suddiviso in quattro fasi principali: preparazione, costruzione, pulizia e post-trattamento.


Processo di Stereolitografia

  1. The preparation takes place on workstations and provides the placements of supports if necessary for the production of the particular.
  2. The construction of the prototype is controlled by a computer. The laser beam (with powers of the order of a few tens of mW) is located, through a suitable optical system, on the surface of the tank containing the epoxy monomer (in a liquid state). The laser beam triggers a chemical reaction that has the effect of the polymerization and therefore the creation of a solid particle. The movement in the plane of focus of the laser allows the realization of the first section of the prototype. The lift is lowered by an amount equal to the thickness of solidified photopolymer and a blade, or a system of the coating of precision, it covers a section just constructed of a film of liquid monomer. The process continues with the solidification of a next state, which adheres firmly to the section below. 
  3. The process continues until the full completion of the prototype, which will be extracted from the tank by lifting the lift and after it will be cleaned for the next step.
  4. It is clear that, to contain the time of construction, the laser cannot fully solidify the section, but will be limited to its profile and to a certain number of lines connecting the inner perimeter with the outer one, creating a honeycomb structure. At the end of this stage, the particular (green part) is completely solidified outside but not completely inside. Its physical consistency is not yet acceptable, so the prototype must undergo a post-treatment to complete the polymerization process. This latter step consists in exposing the particular to an ultraviolet lamp: the duration of this process is a function of the size of the detail. In this way, the polymerization of the liquid resin, still trapped inside the workpiece (which is at this point called red part), would be completed. Then an operator provides to the removal of any support in the particular and also to the finishing of the workpiece.