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Additive manufacturing (earlier known as Rapid Prototyping) is a layer-by-layer fabrication process (Frizziero, Donnici, Liverani, & Dhaimini, 2019). With the advent of time, Rapid Prototyping (RP) processes have evolved as solid, liquid, and powder-based RP process (Pathak & Singh, 2017; Suresh & Narayana, 2016). Among these, the selective laser sintering (SLS) process is gaining importance in the industrial sector due to its adaptability with a wide range of materials and no extra support structure requirements.
SLS is a powder-based layered manufacturing process that uses a CO2 laser as a power source for sintering the powder material to get the desired 3D structure. Initially, SLS was developed for polymers, but nowadays it is widely used in producing solid components from a variety of materials in powder form such as thermoplastics, polyamides, composites, metal-polymers, and ceramics (Negi, Dhiman, & Sharma, 2015; Negi, Sharma, & Dhiman, 2015). Automobile, bio-medical, and aerospace industries need and demand lightweight materials (Negi, Dhiman, & Sharma, 2014a; J. Singh, Sharma, & Srivastava, 2018, 2019). Thus, they are extensively investigating and using these low-volume, high-value, lightweight, and custom-designed, functional parts produced by the SLS process (Negi et al., 2014a; Shah, Pinkerton, Salman, & Li, 2010).
A perquisite for executing SLS is a CAD model (of the object to be manufactured). This model can be generated on design software such as AutoCAD, Pro-E, CATIA, etc. Afterward, the generated CAD model is converted to a standard tessellation language (also known as STL) file format in which the model surface is approximated by dividing it in the number of triangles. This file is sliced into layers and every sliced layer of the 3D model is used as an input for the tool path generation.
Figure 1.
Schematic of SLS process [Source: Internet]
As shown in Figure 1, the SLS system consists of a build chamber in the middle where the part is built and two feed chambers across it to store and supply the powder. All three chambers are piston controlled which can move up and down. A powder layer of specified thickness is spread by the feed roller on the part bed in the build chamber. According to the contour information of each layer, the laser scanning of each layer is performed which results in the sintering of powder material. After each scanning, the part bed is lowered by one layer thickness and the process is repeated for a fresh layer of powder until the desired shape is obtained. The major advantage of SLS is that it does not require a support structure because the unsintered powder always surrounds the part being fabricated. It makes SLS suitable for complex part geometries.