Design guidelines for selective laser melting process
Tan, Hui Ling
Date of Issue2017
School of Mechanical and Aerospace Engineering
Increasing widespread usage of additive manufacturing (AM) technology specifically in the areas of selective laser melting (SLM) process has spurred more research. These enable an addition and improvement of the existing knowledge so as to create high-value functional parts for industries such as automotive, aerospace, medical, logistics and transportation. SLM is a complex process as many factors, especially the properties of powder and laser process parameters as seen in the literature review, would affect the final fabricated part geometrical quality (which includes accuracy, precision, repeatability, feature resolution and surface finishing). In order to thoroughly understand and pinpoint the types of factors which play a primary role in affecting the final part, test artefacts are introduced to learn “more” about the SLM process. The test artefact designed for this study will achieve three purposes - determine international tolerance (IT) grade achievable by the SLM process to print the different features, recognize limitations of the process and identify the best location on the substrate which results in the least percentage error (E%) in all features. Factors that contribute to the final results are discussed in detail. SLM process can produce IT grades between 9 and 17 based on the features produced for this study. This range only includes seven out of the nine features used in this study as the angled square fins and lateral wall features are excluded. It is found based on this study that the best location for printing majority of the features is in the inner most area, opposite from the viewing window and on the right side where the argon gas is released into the working chamber. This best location is found based on the rankings of each of the nine individual features on their specific parameters. With the accumulation of the rankings, the overall best location can be identified. This study also determined the capability of the SLM process. It is found that the diameters for holes of 0.2 mm cannot be print at all. The pins and thin wall thickness of 0.2 mm diameters and 0.2 mm in thickness respectively can be printed either completely or partially. However, those printed are bound to display some form of flaws. These flaws include tilts, incomplete printing, inability to print, breakage and size printed becomes larger than the nominal size specified in the virtual CAD file in SolidWorks. Compared to printing features with small dimensions, those with larger dimensions tend to give very small error percentage such as the cylinder of diameter 8 mm as compared to the other diameters of 5 mm and 2 mm. Also, in order to print a minimum angle without any sign of tail end warping, it is found to be an angle more than 35°. From this study of all nine features, it is found that careful considerations of dimensions and angles are important if a defect-free part is to be printed. As such, a set of guidelines is prepared based on this study for future reference.
Final Year Project (FYP)
Nanyang Technological University