Multiplexed 3D Printing of Thermoplastics

Abstract

Extrusion-based additive manufacturing of large thermoplastic structures has significant emerging 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 Multiplexed Fused Filament Fabrication (MF3) 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. 3D geometric complexity is realized by rastering the extruder array across the smallest rectangle bounding each 2D layer and by spatially specific deposition via “dynamic” filament retraction/ advancement in the extruders. The dynamic moniker is because, unlike conventional single extruder 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, geometrically-limited throughput of the dual-extruder strategy, cost and geometric limitations of robot-based multiplexing, and the complexity and geometric limitations of previous gantry-based multiplexing efforts. Our experiments reveal the parameters that affect dynamic retraction and 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 MF3 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 MF3 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 MF3 to achieve similar or greater throughput than state-of-the-art Big Area Additive Manufacturing while significantly enhancing the geometric resolution.