Session: 03-02-02: Advanced Manufacturing

Paper Number: 121607

121607 - Obliteration of Semi-Porous Construction Lattices for Ti6al4v Laser Powder Bed Fusion Structure With the Cavitation Abrasive Surface Finishing Method 

Laser Powder Bed Fusion (LPBF) using Ti6Al4V is emerging as a viable new transformational additive technology for manufacturing complex shapes of structure that include design features that were not possible with common metallic subtractive, casting, welding or other joining production methods.  In many instances, thin-walled sections must be supported with strengthening aides that are added within the build envelope for the purpose of bracing during the additive manufacturing melting & cooling process.  The support webbing is needed to avoid cracking that can be caused by the high thermal gradients that develop within the build and especially by the shrinkage thar occurs during solidification in local areas of the build planes as they are grown up higher layer-by-layer.  Having completed their function, the supports must later be removed from the excess areas of the parts and this is often accomplished by hand with methods such as hammer & chisel, prying with pliers, band sawing, filing, grinding and sanding. 

An automated machine that makes use of the Cavitation Abrasive Surface Finishing (CASF) process, built by Sugino Machine Ltd. (Sugino), has been utilized in this study as a means of removing semi-porous construction lattices from LPBF Ti6Al4V builds that are representative of sub-scale aerospace hardware such as jet engine fan blades and other generic shapes.  CASF is a hybrid abrasive finishing method that combines the traditional waterjet cutting process with the effects of a special high-pressure water nozzle that has been developed to generate a highly intensive cloud of imploding water vapor cavitation bubbles within a stream of water - which is centered about 100 mm below the cavitation generating nozzle.  Powerful plumes of rotating shock wave power bursts transmit kinetic energy to the abrasive particles acting within the slurry of water and the abrasive particles located inside the processing tank.  The multi-directional spinning cloud cluster of abrasive particles is aimed to surround the target part with a swarming bath, roughly 75 mm wide and 150 mm in total length, which is powerful enough to obliterate the porous build structure from the parts, as well as to blow off most of the partially fused particles, remove contaminants and improve the surface texture. 

For this test, the LPBF sample test pieces were secured on a processing stage and subjected to the blast of the CASF in several modes of operation.  Erosion and obliteration of the porous build structure support lattices were observed to occur at measurable material removal rates (MRR) as a function of the CASF process variables such as water pump pressure supplied to the nozzle, water flow rate, stand-off distance from the nozzle, percentage of abrasives by weight within the slurry, and total surface treatment exposure time.    

Optical examinations and quantifiable surface data measurement scans were performed on the support lattice areas of the test parts both before and after CASF processing.  A correlation study has been made between the performance characteristics such as MRR, surface finish parameters that were achieved and the CASF process dependent variables.  Conclusions are made in regards to the current process capability and future development opportunities. 

Presenting Author: Daniel Sanders Sugino Machine Ltd

Presenting Author Biography: Daniel G. Sanders, FSME, FASM started his career in industry as a machinist in 1977, which led him to become an accomplished tool & die maker. He completed a PhD in Mechanical Engineering at the U.W. (2008). As a Senior Technical Fellow for Boeing Research & Technology, he worked to develop innovative manufacturing & materials technologies for aerospace products. At Sugino Machine Ltd, he is working with a team of manufacturing machine tool development experts to create a new line of automated machines for surface finishing additive manufactured metal parts.