Date of Award
Master of Science (MS)
Georges M. Fadel
Direct Metal Laser Sintering (DMLS) is a specific type of additive manufacturing that is used to create metal parts. In this process, an optical laser is used to melt a metal powder, fusing the powder into a solidified form. The laser follows instructions from a CAD model, which illustrates the design and from which the layer pattern the laser should follow is extracted. A scan path is generated for the laser to trace on the powder, that initially follows the perimeter, and then draws parallel neighboring contour lines in the interior of the scanned perimeter to cover the surface and form a consolidated layer.
Currently, there is an issue with DMLS builds; due to the high heat generated by the laser and the uneven cooling patterns of the metal after fusion. Deformations are forming in the design builds after cooling. Today, additive manufacturing technicians and or designers are having to adjust the original CAD files through the use of predictive software to account for the deformations caused by the laser heat. After an extensive literature review, it was confirmed that the scanning pattern the laser takes in the DMLS to sinter the powder metal affects the magnitude of the temperature gradient and thus affects subsequent build part deformations.
A simulation that computationally mimics the moving laser heat source in DMLS on a build-part allows for control of the scanning pattern and the number of layers to be scanned and returns the temperature profile of the part as it is built and subsequently cooled. A genetic algorithm is tied to the simulation in order to optimize the scanning pattern of the laser with the ultimate goal to reduce the overall temperature gradients induced on the build part. The effects of layer build-up were also investigated with the optimization of the scanning pattern of the laser. The combination of the DMLS simulation and Genetic Algorithm application show qualitatively that optimal scanning patterns can reduce the temperature gradients from the DMLS process. This research work is meant to be a basis for the optimization of scan pattern on specific build part designs and be able to be applied to a wider array of designs as well as in-situ DMLS builds in the future.
Buck, Caroline Victoria, "Scanning Pattern Optimization to Reduce Temperature Gradients in DMLS" (2020). All Theses. 3332.