Microwave Quantification of Porosity Level in 3D Printed Polymers

Additive manufacturing (or 3D printing) of polymers is a powerful technique for rapid prototyping and production of functional parts. However, these techniques, and in particular the fused filament fabrication (FFF) process, can result in parts with relatively large volume of porosity (i.e., distributed air voids). Such undesired levels of porosity can be potentially detrimental to the integrity of a printed part and ultimately limit its use. Microwave material characterization techniques are great candidates for evaluating such porosity, particularly for polymers (i.e., dielectric materials), with the ultimate potential of use for inline process control. In this work the well-known completely-filled waveguide technique is used to measure the complex permittivity of several printed samples with varying controlled porosity levels. Subsequently, two existing dielectric mixing models are used to correlate permittivity to this parameter for quantification purposes.