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Additive manufacturing, such as 3D printing, offers unparalleled opportunities for rapid prototyping of objects, but typically requires simultaneous building of solid supports to minimize deformation and ensure contact with the printing surface. Here, we theoretically and experimentally investigate the concept of material extrusion on an “air bed”—an engineered ultrasonic acoustic field that stabilizes and supports the soft material by contactless radiation pressure force. We study the dynamics of polylactic acid filament—a commonly used material in 3D printing—as it interacts with the acoustic potential during extrusion. We develop a numerical radiation pressure model to determine optimal configurations of ultrasonic transducers to generate acoustic fields and conditions for linear printing. We build a concept prototype that integrates an acoustic levitation array with a 3D printer and use this device to demonstrate linear extrusion on an acoustic air bed. Our results indicate that controlled interactions between acoustic fields and soft materials could offer alternative support mechanisms in additive manufacturing with potential benefits such as less material waste, fewer surface defects, and reduced material processing time.
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Nonlinear and linearized gray box models of direct-write printing dynamics
Purpose The purpose of this study is to develop nonlinear and linearized models of DW printing dynamics that capture the complexity of DW while remaining integrable into control schemes. Control of material metering in extrusion-based additive manufacturing modalities, such as positive displacement direct-write (DW), is critical for manufacturing accuracy. However, in DW, transient flows are poorly controlled due to capacitive pressure dynamics – pressure is stored and slowly released over time from the build material and other compliant system elements, adversely impacting flow rate start-ups and stops. Thus far, modeling of these dynamics has ranged from simplistic, potentially omitting key contributors to the observed phenomena, to highly complex, making usage in control schemes difficult. Design/methodology/approach The authors present nonlinear and linearized models that seek to both capture the capacitive and nonlinear resistive fluid elements of DW systems and to pose them as ordinary differential equations for integration into control schemes. The authors validate the theoretical study with experimental flow rate and material measurements across a range of extrusion nozzle sizes and materials. The authors explore the contribution of the system and build material bulk modulus to these dynamics. Findings The authors show that all tested models accurately describe the measured dynamics, facilitating ease of integration into future control systems. Additionally, the authors show that system bulk modulus may be substantially reduced through appropriate system design. However, the remaining build material bulk modulus is sufficient to require feedback control for accurate material delivery. Originality/value This study presents new nonlinear and linear models for DW printing dynamics. The authors show that linear models are sufficient to describe the dynamics, with small errors between nonlinear and linear models. The authors demonstrate control is necessary for accurate material delivery in DW.
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- Award ID(s):
- 1919204
- PAR ID:
- 10313595
- Date Published:
- Journal Name:
- Rapid Prototyping Journal
- Volume:
- 26
- Issue:
- 10
- ISSN:
- 1355-2546
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1108/RPJ-12-2018-0303
