Research on deposition toolpath planning and laser head Z-axis rising height setting for directed energy deposition

In this study, the biggest goal was using laser directed energy deposition (L-DED) process to fabricate a solid blade part. In the process of CAD modeling, a blade model was built by sweeping a blade cross-section and twisting 10° simultaneously, which made it to have overhanging and tilting features. So, to select an appropriate deposition toolpath was the most important thing. The deposition toolpath in this study was decomposed into contour and field toolpaths. First of all, a cuboid part model of which the geometry was simpler was created to test toolpath planning approaches. The results recommended to use “Fixed rising height per layer with proper laser head rising height (Z-offset setting)” or “Spiral” approaches to plan contour toolpaths. For field toolpaths, “Reciprocating zigzag” planning approach was suggested and it needed to adjust the cladding angle to fit the cross-section of the parts. According to the test results of cuboid part fabrications, the contour of the target blade part was successfully manufactured with a 50% Z-offset setting and the spiral toolpath. The solid blade fabrication was also finished with a fixed rising height per layer with a 50% Z-offset setting and 45° reciprocating zigzag toolpath. In addition, the relationship between the Z-offset setting and the dilution was investigated through experiments. A conjecture that a height shrinkage of an old layer caused by thermal deformation is equal to the single-layer deposition dilution was proposed. Based on this conjecture, users can improve L-DED deposition results by setting the Z-offset as “the product of single-track height and the degree of shrinkage of an old layer height.” By combining the predictive value of dilution surface fitting model with the conjecture, it can be easier to get better LDED deposition quality.