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When air moves across a surface, such as a high-speed web, a boundary layer is formed. This layer
can build to substantial thickness, trapping and carrying particles with a diameter less than the boundary layer thickness. A web moving at 1500 ft/min for example, can form a layer larger than 1 inch,
allowing even large particles to remain trapped.
Typical vacuum systems are not able to break up or penetrate this layer and thus cannot remove the
smaller particles.
Conventional air knives can reduce the thickness of the boundary layer by directing high velocity
air along the substrate. This method, however, has severe limitations, since in the process of overpowering the web’s boundary layer, the air knife creates a new thinner boundary layer, perhaps 50 to 100
microns thick. Larger particles can be removed, but small particles are still trapped in this newly created boundary layer.
The only effective solution to removing the trapped fine particles is to utilize an agitating
method to disrupt or penetrate the boundary layer. The ultrasonic nozzle of the Micro Cleaner superimposes high frequency pulses over a high pressure, high velocity flow to impart very high energy levels
to the substrate. These pulses knock the trapped particles out of the boundary layer so they can be removed by the vacuum without any damage to the substrate.
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