Progress in Additive Manufacturing· 2026Q1
Local activation of porosity in fused filament fabrication by in-nozzle physical foaming with supercritical CO2
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- Q1SCImago
- 2026year
Short summary
A new method enables physical foaming inside an FFF printer nozzle using supercritical CO2, achieving 75.3% porosity in PETG strands without additives.
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Key points
- Physical foaming is achieved inside the FFF nozzle using supercritical CO2 injected through a lateral port.
- A static mixer aids CO2 dissolution in the polymer melt before foaming at the nozzle exit.
- PETG strands printed with this method exhibit an overall porosity of 75.3% (70.0–79.8%).
- Foamed strands show a distinct structure with a denser outer skin and a more porous core.
- The process initiates pore formation locally on demand, without requiring additional foaming additives.
AI-generated from the title and abstract; the full text is not read.
Abstract
Abstract Material extrusion of thermoplastics (fused filament fabrication, FFF) commonly deposits solid strands. Foams combine low density with functions such as damping and thermal insulation, making cellular strands a desirable extension of FFF. We demonstrate dissolution-assisted physical foaming inside the nozzle of an FFF system: an external gas booster supplies supercritical CO 2 through a lateral port into the melt, and a static mixing element upstream of the 0.60 mm nozzle promotes dissolution before foaming occurs at the nozzle exit. This transfers inline gas dosing and melt homogenization, established in foam extrusion, into an FFF printhead. We printed foamed strands and ring-shaped specimens from PETG and characterized them by microscopy and micro-computed tomography (µCT). Full-volume µCT analysis yielded an overall porosity of 75.3% (70.0–79.8% across segmentation thresholds), with a denser skin surrounding a more porous core. Using only gas, the polymer remains free of foaming additives, and we initiated pore formation locally on demand through the gas supply alone.
The authors' abstract, as published at the source. Progress in Additive Manufacturing, 2026 · DOI ↗
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Field: Polymers and Plastics
Polymers and PlasticsMaterials Science