Demonstration of Closed Loop Inspection and Repair Using Layer Topographic Mapping with L-PBF
AM in-process inspection methods like melt pool monitoring typically don’t provide accept/reject guidance. When flaws are detected, they don’t provide the operator with the instructions to repair the flaw and salvage the build where this may be possible.
Flightware demonstrated the development of this capability using a non-thermal in-process inspection method on every layer. Layer topographic mapping (LTM) is an in-situ inspection method using an optical profilometer to acquire a dense, precise map of layer surface height. Algorithms process this data to detect melt flaws with excellent performance. Flightware demonstrated detection of lack of fusion flaws in more than 1,800 Inconel 625 layers is 98.2% probability of detection (POD) and 1.0% probability of false detection (POFD). Optimum repair/rework processes were developed for lack of fusion flaw regions 1 to 3 layers thick. LTM software was modified to not only detect flaws but also define the optimum repair process to employ upon detection based on the number of flaw layers present. Intentionally created (or seeded) lack of fusion flaws, were restored to less than 0.1% porosity for 1 to 3-layer flaws. Porosity in the flaw regions was reduced by up to 99%.