SUNY Distinguished Professor University at Buffalo, The State University of New York
Electrical methods of 3D-printing process monitoring involve the 3D build sensing its own condition with no sensor involved. Having no device involved results in low cost, high durability, no mechanical property loss, design simplification, and large sensing volume. This constitutes structural self-sensing. The science is based on structure-property relationships. The properties are the electrical properties. The electrical methods are fast and inexpensive. Rapidity enables real-time monitoring and smart manufacturing. In contrast to cameras, they are amenable to sensing sub-surface defects such as interlayer defects. Techniques not amenable to real-time monitoring or small defect detection include X-ray computed tomography, microscopy, ultrasonic inspection, eddy current inspection and vibration-based testing. For nonconductive materials such as polymers, capacitance measurement is suitable. For conductive materials such as metals and polymers with conductive fillers, resistance and inductance measurements are suitable. Resistance measurement requires electrodes of higher quality than inductance measurements, due to the electrode-print interface resistance contributing to the measured resistance. Furthermore, the inductance is more sensitive to current path direction changes than the resistance, due to Faraday’s law. The measured electrical quantities include the impedance, reactance, resistance, capacitance, inductance, and θ (the angle between the complex impedance and its real part, the resistance). The information obtained includes the stress, damage, infill angle, shape, and surface roughness. In particular, the electrical quantities are affected by in-plane defects (e.g., voids), interlayer defects, and the printed line orientation relative to the electrical measurement direction. The impedance increases with the infill angle. The interception of the electric field lines from one electrode to the other by a defect affects the electrical quantities (e.g., decreasing the capacitance), with the degree of the effect being sensitive to the position of the defect. Defects can also reduce the permittivity, thereby decreasing the capacitance. Surface roughness and shape complexity change increase the inductance.
Learning Objectives:
Upon completion, participants will be able to understand the concepts of electrical monitoring, including the electrical quantities and the associated science.
Upon completion, participants will be able to understand how the electrical methods can be used for 3D printing monitoring and the capabilities of the methods.
