An active nozzle with variable shape: Introduction and exploration of impact for silicone DIW

Additive manufacturing of silicone parts using Direct Ink Writing is interesting for producing parts with complex geometries, especially for medical applications and soft robotics. Using commercially available off-the-shelf solutions, the process currently relies on the choice by the user of a standardized rigid nozzle prior to printing. The nozzle orifice dimensions must then respect a trade-off between resolution and control over manufacturing time: a small-diameter nozzle allows for higher printing precision, but at the cost of longer printing times. Furthermore, in the case of a non-Newtonian fluid such as silicone, the internal geometry of the nozzle channel directly affects the shape of the extruded bead. A solution based on a variable-geometry nozzle is presented to contribute to the development of active nozzles. It relies on a deformable body, actuated by nine independent actuators, permitting continuous variation of the shape and dimensions of the orifice during the printing process, and also independently of the internal geometry of the nozzle. The proposed solution enables the independent displacement of the orifice from the printer end-effector. The staged configuration of the nozzle also makes it possible to act on flow dynamics. The behavior of the nozzle is assessed in printing conditions, and the associated results show that the nozzle is capable of producing beads of variable diameter, reducing printing time. The displacement of the position of a printed bead, independently of the end-effector of the printing structure, is highlighted, and a direct influence on fluid dynamics at the nozzle output is observed. • A nozzle with active control of orifice size and overall shape is proposed. • Orifice size can vary from 0.32 to 1.11 mm, reducing a sample printing time by 50%. • The nozzle mobilities can be used in conjunction with the printing system motion. • The nozzle motions are shown to provide possible improvement of printing accuracy. • Using nozzle shape modification can help to control the material flow.