Multi-Section Nozzle Geometry for High Viscosity Jetting
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Solution Overview
Problem
Existing printheads face challenges in forming desirable droplets with high viscosity print fluids, as the jet becomes excessively long due to dominant viscous forces, leading to late break-off and long ligaments that do not merge into the jet head.
Innovation Solution
The implementation of nozzle geometries with converging and uniform sections, followed by another converging section, creates velocity differences in the print fluid, inducing instability and accelerating the break-off time, thereby reducing ligament length and improving droplet formation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of moving object
If conventional nozzle geometries are used with high viscosity print fluids, then the jet becomes excessively long due to dominant viscous forces, but this leads to late break-off and long ligaments that do not merge into the jet head
Solution Approach 1:
The patent modifies the nozzle geometry parameters, specifically implementing a multi-section converging design with different convergence angles (first converging section with angle α1, second converging section with angle α2 where α2 < α1). This geometric parameter change creates velocity differences in the print fluid that induce instability, accelerating break-off and reducing ligament length to form desirable droplets even with high viscosity fluids
2Loss of time
If the convergence angle of the nozzle is increased to accelerate fluid flow, then break-off time is reduced, but this may cause excessive turbulence and instability in the jet
Solution Approach 1:
The nozzle is divided into multiple sections: a first converging section with a steeper convergence angle (α1) to accelerate flow and reduce break-off time, and a second converging section with a gentler convergence angle (α2) to stabilize the jet. This segmentation allows different parts of the nozzle to perform different functions - the first section promotes break-off while the second section maintains jet stability
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This design enhances droplet formation by reducing ligament length and accelerating break-off, particularly effective with high viscosity print fluids, resulting in fewer satellites and improved jetting characteristics.
Implementation Method 1
In jetting these types of print fluids, the jet becomes exceedingly long as the viscous forces dominate over inertial forces
Implementation Method 2
surface tension forces pulling the liquid into a spherical droplet
Implementation Method 3
viscous forces dominate over inertial forces
Implementation Method 4
The shape of the nozzles described herein creates a difference in speed of the print fluid, and causes an artificial instability within the jet
Data Source
AI summary
Printheads for a jetting apparatus. In one embodiment, a printhead comprises a plurality of nozzles configured to eject a print fluid. Each nozzle is comprised of a first converging section having a cross-sectional area that decreases in a flow direction of the print fluid through the nozzle, a neck adjoining the first converging section and having a cross-sectional area that is uniform in the flow direction of the print fluid through the nozzle, and a second converging section adjoining the neck and having a cross-sectional area that decreases in the flow direction of the print fluid through the nozzle.