High throughput extrusion additive manufacturing – rate limits and system design

Abstract

Fused filament fabrication (FFF) is an additive manufacturing (AM) process in which a polymer feedstock is melted and extruded through a nozzle while guided by a motion system, resulting in a three-dimensional part. FFF is applicable across a range of length scales and with a wide variety of thermoplastic polymers and composites. As such, FFF is increasingly used in prototyping, low volume production, and tooling/fixture applications.

One of the drawbacks to FFF is its low build rate, which is limited by the fundamentally serial nature of the process–a single printhead must traverse a trajectory that spans the entire built volume of the part while depositing material. As a result, the build rate is governed by the performance of the motion and extrusion systems. This thesis explores the influence of motion and extrusion system design on FFF build rate by: 1) deriving a set of design rules for FFF systems that maximize rate, subject to specified quality constraints and guided by finite element analyses and parametric models; 2) the mechanical design and construction of a servo-driven FFF testbed that uses a parallel H-frame belt drive; and 3) implementing closed-loop servo control with the aforementioned hardware and assessing axis-level motion performance and overall print quality using test artifacts. Performance of the custom-built FFF system is benchmarked against the models in (1), and against commercial FFF systems, and rate-resolution tradeoffs are quantified. This thesis concludes with suggestions for further machine design and process control improvements for FFF AM.