Investigating Shrinkage: CAD, Thermal and Volumetric for Selective Laser Sintering of Polyamide Parts

Selective laser sintering (SLS) is an additive manufacturing (AM) process, which is widely used for fabrication of end used products, directly from computer aided design (CAD) data. SLS process is usually used in different areas such as biomedical, automobile and aerospace industries. The major advantage of this process is that the designer can visualize and test the specimens before the full scale production of parts. Therefore, to achieve a good dimensional accuracy in order to fulfill the demands of these fields is a key parameter. Dimensional accuracy of SLS process is mainly influenced by geometry, process parameters and materials. It can only be enhanced by controlling the shrinkage of parts. Therefore, this work is carried out to analyze the effect of crucial contributing factors (i.e, laser power, bed temperature, layer thickness, scan spacing and orientation) for the shrinkage (CAD, thermal and volumetric) of duraform polyamide specimens. Face centered central composite (CCD) design is used for the collection of data. Response surface methodology (RSM) is used to monitor the effects as well as interactions of selected parameters, and for the development of regression models. Multi-response optimization of shrinkage along with composite desirability is employed for different optimized selected SLS parameters. It has been found that the laser power 41 W, bed temperature 170 °C, layer thickness 0.09 mm, scan spacing 0.15 mm and orientation 85.68 degree is a most significant optimized range of these parameters to improve the overall shrinkage measures of parts.