Effect of Laser Power on Component Strength in Laser Sintering

Abstract

Prototyping or model making is one of the important steps to finalize a product design. It helps in conceptualization of a design. Before the start of full production a prototype is usually fabricated and tested. RP processes namely Stereo-lithography (SL), Selective Laser Sintering (SLS), Fused Deposition Modeling (FDM) and Laminated Object Manufacturing (LOM) are described. In Selective Laser Sintering (SLS) process, fine polymeric powder like polystyrene, polycarbonate or polyamide etc. (20 to 100 micrometer diameter) is spread on the substrate using a roller. Before starting CO2 laser scanning for sintering of a slice the temperature of the entire bed is raised just below its melting point by infrared heating in order to minimize thermal distortion (curling) and facilitate fusion to the previous layer. The laser is modulated in such a way that only those grains, which are in direct contact with the beam, are affected. Once laser scanning cures a slice, bed is lowered and powder feed chamber is raised so that a covering of powder can be spread evenly over the build area by counter rotating roller. In this process support structures are not required as the un-sintered powder remains at the places of support structure. It is cleaned away and can be recycled once the model is complete. This research has examined the effect of Laser power as well as processing parameters on the mechanical properties of selective laser sintered parts from DURAFORM PA In this research tensile specimens of Polyamide (DURAFORM PA) material as per the test standard ‘ASTM D638’ are fabricated. This test method covers the determination of the tensile properties of unreinforced and reinforced plastics in the form of standard dumbbell-shaped test specimens when tested under defined conditions of pre-treatment, temperature, humidity, and testing machine speed. The effects of varying the Laser power, generated by the laser, on the physical and mechanical properties of produced specimens. The energy density is varied by changing the laser power at a fixed value of laser scan spacing. Knowing the relationship between SLS parameter settings and material properties will make it possible to manufacture parts with predetermined properties, customized for various applications.