Flexographic Anilox Cell Metering Dynamics under High Shear Rate Regimes
Anilox metering under high shear rate regimes depends on ink rheology and blade deflection balance to prevent hydrodynamic lift and coat weight drift.
Micro Cavitation
Vapour Collapse
Rapid creation and collapse of microscopic vapour bubbles in the ink or coating fluid can damage equipment and ruin print quality. The micro cavitation occurs when local pressure drops below the vapour pressure of the liquid, often near the doctor blade or inside anilox cells. This event releases energy that can erode ceramic surfaces and create pinholes in the applied film.
Surface Erosion
Frequent collapsing of bubbles acts like a series of tiny hammer blows against the cell walls. Over time, this force creates pits and cracks in the anilox roll, reducing its ability to meter ink accurately. Using surfactants or adjusting the blade angle can mitigate the pressure drops that lead to bubble formation.
If left unchecked, the resulting surface roughness increases the wear on the doctor blade. The loss of cell wall integrity eventually leads to inconsistent ink delivery across the web. Proper ink circulation and degassing are common methods for controlling this physical phenomenon.
Fluid Stability
Entrained air and collapsing voids prevent the ink from wetting the plate or the substrate evenly. This leads to a mottled appearance or small unprinted spots in solid areas. Reducing the pump speed or using de-foaming agents helps maintain a stable fluid flow and prevents these microscopic disruptions.