Process planning for additive manufacturing of geometries with variable overhang angles using a robotic laser directed energy deposition system

Advancements in 3D Printing: Directed Energy Deposition Techniques, Defect Analysis, and Quality Monitoring

“…The overhanging structure, improper defocusing distance, and improper energy density can further aggravate the edge collapse and powder adhering to the sidewall, leading to a severely uneven surface, low dimensional accuracy, and an increased need for post-processing or even material wastage [135]. This is because the unsupported overhanging structure's horizontal offset ∆y increases dramatically with the inclination angle θ and z-increment ∆z, resulting in the staircase effect and leading to an unstable flow of the deposition molten pool liquid metal, ultimately resulting in collapse [144,147]. Employing sensors to ensure proper energy density coupled with the use of an appropriate scanning strategy, such as starting with a contour followed by infill, should minimize side collapse [16,88,129,148].…”

“…For active sensors, laser triangulation offers high resolution and accuracy for surface measurements and is often found to be used for layer height control [141,[206][207][208][209]. Structured light, on the other hand, provides detailed 3D models but requires controlled lighting and can be time-consuming and difficult to utilize for complex parts [147]. Though laser triangulation and structured light may be favourable in regard to the measurement of surface roughness, object size, and measurement accuracy, they struggle with highly reflective or absorptive surfaces, such as those found in finished metal AM [141,176,[206][207][208][209][210][211][212].…”