Browsing by Subject "impedance-based monitoring"

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In-situ Detection of Build Defects in Additive Manufacturing via Impedance-Based Monitoring
(University of Texas at Austin, 2016) Sturm, Logan; Albakri, Mohammed; Williams, Christopher B.; Tarazaga, Pablo
In this paper, the authors explore the use of impedance-based monitoring techniques for the in-situ detection of additive manufacturing build defects. By physically coupling a piezoceramic (PZT) sensor to the part being fabricated, the measured electrical impedance of the PZT can be directly linked to the mechanical impedance of the part. It is hypothesized that one can detect in-situ defects of part mass and stiffness by comparing the signatures collected during printing of parts with that of a defect-free control sample. In this paper, the authors explore the layer-to-layer sensitivity of this technique. A control sample is created using Material Jetting and the change in signatures between various layer intervals is measured. To evaluate the technique’s ability to perform in-situ detection, several parts containing designed defects (e.g., internal voids) are fabricated and their layer-to-layer signatures are compared to a control sample. Using this technique, the authors demonstrate an ability to track print progress and detect defects as they occur.
Non-Destructive Evaluation of Additively Manufactured Parts via Impedance-Based Monitoring
(University of Texas at Austin, 2015) Albakri, Mohammed; Sturm, Logan; Williams, Christopher B.; Tarazaga, Pablo
The ability of Additive Manufacturing (AM) processes to fabricate complex geometries is somewhat hindered by an inability to effectively validate the quality of printed complex parts. Furthermore, there are classes of part defects that are unique to AM that cannot be efficiently measured with standard Quality Control (QC) techniques (e.g., internal porosity). Current QC methods for AM are limited to either destructive evaluation of printed test coupons, or expensive radiation-based scanners of printed parts for non-destructive evaluation. In this paper, the authors describe their use of impedance-based structural monitoring to indirectly measure printed part abnormalities. By bonding a piezoceramic (PZT) sensor to a printed part, the measured electrical impedance of the PZT can be directly linked to the mechanical impedance of the part. By observing deviations in the mechanical impedance of the part, as determined by this quick, non-intrusive electrical measurement, one is able to detect the existence of part defects. In this paper, the authors explore the effectiveness and sensitivity of the technique as a means for detecting of a variety of defect types and magnitudes.