Quality Control of 3D-Printed Polymer Parts

The Challenge

As FDM 3D printing scales for production applications, internal defects, voids, delamination, and density variations, become critical quality concerns. These flaws are invisible from the surface but compromise mechanical performance. Traditional inspection methods are either destructive or too slow for production-rate screening.

The Solution

Impulse excitation testing reveals internal defects through their effect on modal properties. This research tested polyamide samples with controlled defects (0–10 mm) at the neutral bending line, measuring peak frequency, damping, and amplitude using both acoustic and vibration sensors.

Key findings: vibration detectors excel at detecting delamination in larger defects (7–10 mm), while acoustic detectors better evaluate defect size and position. Small defects (3 mm) show elevated frequency from local hardening at defect edges. The choice of detector matters. Each type reveals different defect characteristics.

Key takeaway: Acoustic and vibration sensors reveal complementary defect signatures in FDM parts, meaning sensor selection must match the target defect type for reliable quality screening.

Results

The research demonstrates that IET provides reliable non-destructive detection of internal defects in FDM polyamide parts. By correlating modal response patterns to specific defect types, manufacturers can implement 100% inspection of 3D-printed polymer components without slowing production.