Title: Demonstration of Closed Loop Inspection and Repair Using Layer Topographic Mapping with L-PBF

Authors: David Maass

DOI: 10.33599/nasampe/c.19.0693

Abstract: AM in-process inspection methods like melt pool monitoring typically do not provide accept/reject guidance. Even when flaws are detected, they do not provide Operator instructions to repair the flaw and salvage the build, in cases where this is possible. The work described here demonstrates the development of such capability using a non-thermal in-process inspection method on every layer.

Layer Topographic Mapping (LTM) is an in-process inspection method using an optical profilometer to generate a dense, precise map of layer surface height. Algorithms process this data to detect melt flaws with excellent performance. 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 0.15% porosity for 1 to 3-layer flaws. Porosity in the flaw regions was reduced by up to 99%.

References: 1. Rehme, O., “Cellular Design for Laser Freeform Fabrication”, Volume 4 of Schriftenreihe Lasertechnik, Cuvillier, 2010 2. Maass, D., Boulware, P., Richter Lamorte, C., Mendoza, H., “Novel Inprocess Inspection Method for Additive Manufacturing”, Composite and Materials Expo (CAMX), Dallas TX, October 2018 3. Maass, D. “Formed Layer In-Process Inspection for Powder AM Processes”, RAPID + TCT Conference, Detroit, MI, May 23, 2019 4. Quantitative Assessment of Conventional Nondestructive Inspection Techniques for Detecting Flaws in Composite Laminate Aircraft Structure, DOT/FAA/TC-15/6, March 2016 5. Dept. of Defense Handbook “Nondestructive Evaluation System Reliability Assessment”, MIL-HNBK-1823A, April 24, 2004

Conference: CAMX 2019

Publication Date: 2019/09/23

SKU: TP19-0693

Pages: 14

Price: $28.00