ORIGINAL RESEARCH article
Front. Mech. Eng.
Sec. Digital Manufacturing
This article is part of the Research TopicGlobal Excellence in Digital Manufacturing: Europe Vol. 2View all articles
Supportless Overhanging Structures via Piezoelectric Droplet-Based Material Extrusion
Provisionally accepted
- Universita degli Studi di Firenze Dipartimento di Ingegneria Industriale, Florence, Italy
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Piezoelectric material extrusion is a novel material extrusion technique that deposits thermoplastic materials in droplets, by means of a piezoelectric nozzle regulating the material flow. This improves the performance of the machine, with respect to Fused Filament Fabrication, by enabling higher precision in material placement and better control over deposition volume. A common limitation of this technology lies in the fabrication of overhanging structures, where precise droplet deposition is inherently more complex and prone to inaccuracy. The research investigates the impact of a key process parameter, specifically Droplet Aspect Ratio, on the dimensional accuracy of printed specimens and on the quality of overhang surfaces. The research considers bridging and the prioritization of infills in the deposition strategy as additional variables. An experiment based on the fabrication of 50 specimens, optimized for overhang quality evaluation, was performed. Specimens were analysed through 3D scanning techniques. The study demonstrates a strong correlation between Droplet Aspect Ratio and the dimensional accuracy of overhanging surfaces. The integration of bridging structures significantly improved surface quality by providing additional support, with the greatest benefits observed at 27° inclination. Prioritizing infill deposition before outer contours resulted in a marked reduction in defect levels at high DAR values.
Keywords: Additive manufacturing, droplet aspect ratio, Overhang, pellet-based material extrusion, Piezoelectric nozzle
Received: 01 Oct 2025; Accepted: 28 Jan 2026.
Copyright: © 2026 Buonamici, Furferi, Carfagni, Tapinassi and Volpe. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) or licensor are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.
* Correspondence: Rocco Furferi
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