3D Printing with 6D of Freedom: Controlling Material Extrusion Speed

Abstract

3D printing is conventionally performed with manipulators with only three degrees of freedom (DOF), resulting in objects consisting of horizontal layers and inherent weakness in the vertical direction. This shortcoming is mitigated by printing along curved surfaces, which requires manipulators with more degrees of freedom, a new way of trajectory planning, and a dynamic control of material extrusion speed - the issue addressed in this paper. Our printing set-up, which we describe in the paper, includes an industrial 6 DOF manipulator. The manipulator has non-negligible inertia as well as other limiting constraints, and thus fails to achieve the programmed speed on many of the printing path segments leading to either overflow or underflow of material and poor object quality. We develop a simple empirical approach to predict the speed on problematic path segments and adjust the speed of extrusion, ensuring the correct amount of material is deposited.