DETECTION OF ARTIFICIAL DISCONTINUITIES LOCATED IN DIFFERENT LOCATIONS IN PLA SPECIMENS MANUFACTURED WITH MEX AT DIFFERENT LAYER THICKNESSES BY ULTRASONIC INSPECTION

PLA (polylactic acid) is the most commonly used polymer in material extrusion-based additive manufacturing (MEX), which is one of the most innovative methods in the production of polymers. Its biodegradability, availability, and low cost drive its widespread use. Due to the nature of additive manufacturing, some discontinuities tend to occur in the production of polymer materials. Discontinuities such as junction problems between layers, voids, and solidification of extruded polymers occur between the production of layers. Non-destructive testing methods can be used to detect these discontinuities. Ultrasonic testing, a volumetric Non-destructive testing method, is well-suited to detect such discontinuities. This study evaluates how layer thickness influences ultrasonic detection of discontinuities in MEX-produced PLA specimens. 0.1 mm, 0.2 mm, and 0.4 mm layer thicknesses of PLA specimens, each of which has artificial discontinuities (holes) placed at different depths and locations, were analyzed by the ultrasonic inspection technique. In the experimental studies, sound waves were sent to the specimens, and the reflected echoes were evaluated. Results show that layer thickness alters echo amplitude and the positional accuracy of detected discontinuities. In specimens with a layer thickness of 0.1 mm, the detection of discontinuities was clearer, while in specimens with a layer thickness of 0.4 mm, the sound echoes were more scattered, negatively affecting the measurement accuracy. These findings clarify how manufacturing parameters shape Non-destructive testing effectiveness in additive manufacturing and hold practical implications for industry.