Start-up Stage for an Electric Field Assisted Fused Deposition

Electric field assisted Fused Deposition Modeling (E-FDM) is a promising technique in the field of 3D printing. However, large nodes often appear in the start-up stage of printing. When the interval between thin lines is small, large nodes will seriously affect the subsequent printing. In this paper, we will present a method to avoid large nodes in start-up printing according to studies the start-up stage of the printing. The startup stage is a process of liquid gradually deforming and initially contacting the substrate under the action of electric stress. Polycaprolactone (PCL), a popular material for bio-medicine, is selected as the printing material. With a home-build E-FDM system, the nozzle substrate distance is fixed, and the nozzle and substrate temperatures are holding steady. With a photography system, the process of meniscus deformation is recorded. And by image processing methods, the meniscus length and volume of liquid at the nozzle can be obtained. At a set of initial liquid volumes (Vi), nozzle voltage is ramped to a fixed value at a fixed rate. The effects of Vi on the meniscus deformation during the start-up stage of the printing are examined. For sufficiently small Vi, the meniscus deforms into a cone shape (Taylor cone), and a jet with a diameter much smaller than the nozzle diameter appears. For sufficiently large Vi, the meniscus exhibits a spindle shape when it touches the substrate. Through this study, it is suggested that for high resolution printing, ramping the voltage at small Vi is preferable.