An experimental investigation into ink transfer using a roller squeegee in high-speed screen printing

Abstract

The paper describes a series of experiments on precision screen-printing with a roller squeegee. The work showed that this could only be achieved using a screen having a high mesh count, notably using a 150-34 screen, since a lower thread count offers insuf cient resistance to ow and leads to image ooding. A detailed investigation into process parameters showed that at up to 60 per cent coverage the performance of a roller squeegee in either sliding and rolling mode is identical. Above this coverage and for smaller snap-off gaps, the roller squeegee constrained to slide led to a higher ink coverage. It is suggested that the main reason for this is the viscosity reduction at the screen surface on account of the ink characteristics and the high local shear rates. This dominates the higher hydrodynamic pressure associated with the rotary motion. However, the rolling action leads to superior tonal gain characteristics. It was observed that, when the squeegee was locked, the screen adhered to the substrate, reducing the snap-off speed and increasing the contact duration. The combined effect led to an increase in ink deposit. When the snap-off gap was increased suf ciently to prevent the screen from adhering to the substrate, the rotating squeegee produced considerably higher ink deposit than the locked squeegee. Presently, this is believed to be due to the increase in hydrodynamic pressure within the squeegee nip junction which now becomes a dominating mechanism.

Pore Structural Characterization of Fuel Cell Layers Using Integrated Mercury Porosimetry and Computerized X-ray Tomography

“…After application of the ink the screen must be withdrawn, and the ink left in the screen must 'snapoff' from the ink on the substrate. The level of temporary adhesion of the screen behind the squeegee to the substrate depends upon the squeegee initial loading and speed, the tension in the screen mesh, and the gap size between the equilibrium (squeegee-free) position of the mesh and the substrate 15 . The tension in the mesh of the screen causes the mesh fibres to withdraw from the substrate.…”

High-speed imaging the effect of snap-off distance and squeegee speed on the ink transfer mechanism of screen-printed carbon pastes

“…[19][20][21] This limits the understanding of the physical mechanisms of ink transfer which occur during screen printing. Computational fluid dynamics (CFD) models have been developed to assess both the Newtonian and non-Newtonian inks 20,22,23 based on mechanisms proposed by 24,25 and Messerschmitt 26 to predict how the ink flows and separates during screen printing. Riemer 24 likened the openings in the mesh to capillaries, forcing the ink into the mesh in accordance with the Hagen-Poiseuille law.…”

Research of paste transition to substrate in LTCC-technology

“…J. Fox, T. C. Claypole and D. T. Gethin (2003) [7] examined the possibility of screen printing with a roller squeegee. The work revealed a lack of roller squeegee -a satisfactory print quality is obtained on a grid of 150-34 or more.…”