Additive manufacturing (AM) is an emerging manufacturing technology in which components are fabricated layer by layer. Among the various additive manufacturing techniques, polymer material extrusion is one of the most widely used processes for producing polymer components. Despite the numerous advantages of this process, the occurrence of defects during manufacturing is inevitable. Therefore, the assessment and monitoring of component integrity, including the determination of material properties and the detection of common defects, still require further investigation. In addition, the development of evaluation methods for nondestructive testing systems specifically designed for AM polymer components is of considerable importance. In this study, a mechanized B-scan system was designed and developed to establish an ultrasonic testing method for the evaluation of polymer components. First, the ultrasonic wave velocity in the components was measured to determine the accurate location of defects based on the measured acoustic properties. The ultrasonic wave velocity was measured as 2165 m/s, with a measurement error of less than 1%, indicating a high level of measurement accuracy. Then, the notch defect in the standard V1 calibration block was used as a reference for designing artificial notches in AM polymer components. In this way, the artificial defects introduced during the fabrication of the components can be represented by notches equivalent to those in the reference calibration block, thereby providing reference defects for evaluating the ultrasonic inspection capability of AM polymer components. Subsequently, the performance of the ultrasonic probes and their resolution capability were evaluated according to the characteristics of the reference block. Ultrasonic tests were then performed using both contact and immersion techniques to compare and validate the two methods. Finally, the performance of the immersion B-scan method was evaluated for locating notches with different dimensions, and an appropriate linear scanning speed in the range of 16–24 mm/min, with an average value of 20 mm/min, was determined as the optimal operating range of the developed system.