Nondestructive quantification of internal raster path for additively manufactured components via ultrasonic testing

This work investigates the viability of discerning the raster pattern of additively manufactured components using high frequency ultrasonic nondestructive testing. Test coupons were fabricated from poly cyclohexylenedimethylene terephthalate glycol using the fused filament fabrication process, in which layers were deposited at various predetermined raster angles. Each printed part was scanned using spherically focused, high-resolution, ultrasonic transducers of various peak frequencies between 7.5 and 15 MHz. From the captured waveform data, images are extracted to observe the raster pattern in a layer-by-layer manner, with the results from the 10 MHz element yielding the best performance. An in-house MATLAB script was developed to analyze the transducer signal to investigate C-scan images at various depths throughout the component. From the resulting C-scan images, one can consistently identify the proper raster orientation within 2°-4° in each of the first 10 deposited layers, with the accuracy decreasing as a function of depth into the component. Due to signal attenuation, there is insufficient data at depths beyond the 11th and 12th layer, to properly analyze the present data sets accurately. Validation was performed using X-ray computed tomography scans to demonstrate the accuracy of the ultrasonic inspection method.