Continuously Variable Orifice Extrusion for Build Time Reduction in Fused Element Fabrication Additive Manufacturing

Abstract

Fused filament fabrication (FFF) is an additive manufacturing technique that extrudes string-like polymeric material through a fixed orifice diameter to build an object layer by layer. This process can last from minutes to hours depending on the size and complexity of the geometry. The selected orifice diameter balances between the possible extrusion widths, extrusion height, and material flow rate. Typically, the selected orifice extrusion width is limited to 130% of its diameter while the extrusion height is limited to 70% of the selected orifice diameter. These limits cause a toolpath design tradeoff between high print speed and fine print resolution. This work presents the design of a mechanism that can vary its orifice diameter to provide continuously variable orifice extrusion (CVOE). The mechanism uses a moving shutter to vary the cross-section area that the material can flow through. Additionally, we demonstrate a novel concept that provides CVOE benefits using a nozzle of a fixed size. The "virtual nozzle" system overextrudes lines that are wider and thicker than what the nozzle is than typical bead widths produced at the given nozzle size. In some cases, test prints completed using the virtual nozzle system can provide up to 40% reduction in print time while maintaining good surface resolution. Overall, this work breaks the tradeoff between speed and resolution, giving faster prints while maintaining or increasing the surface resolution.