Beyond the Throughput-Resolution Tradeoff in Extrusion-based 3D Printing of Thermoplastics

J. Cleeman, B. Mangrolia, R. Malhotra
United States

Keywords: fused filament fabrication, throughput, resolution


Extrusion-based additive manufacturing of large thermoplastic structures has significant next-generation applications. The most popular approach to economically achieving such 3D printing is to increase the polymer flow rate along with the layer height and line width. However, this creates a fundamental compromise between the achievable geometric fidelity and the printing throughput. We explore a Multi-extruder Fused Filament Fabrication (MFFF) approach in which an array of FFF extruders concurrently prints different sections of the same part using small layer heights and line widths. Mounting all the extruders on one cartesian gantry without individual control of each extruder’s motion enables simple machine construction and control. Significant 3D geometric complexity is realized by rastering the extruder array across the smallest rectangle bounding each 2D layer and by realizing spatially specific deposition via “dynamic” filament retraction and advancement in the extruders. The dynamic moniker is because, unlike conventional single nozzle FFF, the extruder array does not stop during dynamic filament retraction/advancement. This achieves higher throughput at greater resolution without material-intensive overprinting and machining, the geometrically-limited throughput of the dual-resolution strategy, the cost and geometric limitations of robot-based multiplexing, and the complexity and geometric limitations of previous gantry-based multiplexing efforts. Our experiments reveal the key parameters that affect dynamic retraction/advancement, and show a previously unknown coupling between the efficacy of dynamic filament retraction and dynamic filament advancement. We create part-scale thermal simulations to model temperature evolution in the part under the action of multiple concurrently acting extruders, revealing a unique temperature history that can affect bonding and mechanical properties. We show that MFFF can enable resilience to extruder failure by allowing other extruders to take over part fabrication while the damaged extruder is being replaced. We also demonstrate that MFFF enables flexibility in part scale and geometry, i.e., the ability to make multiple smaller parts of similar or distinct geometries in one production run and lesser number of larger parts of similar or distinct geometries in the next production run. Finally, we quantitatively analyze the future potential of MFFF to achieve similar or greater throughput than state-of-the-art Big Area Additive Manufacturing while significantly enhancing the geometric resolution.