Aerosol Generation
Ejection of fine droplets from the exit side of a printing nip creates a cloud of airborne particles that settles on machinery and surrounding surfaces. At velocities exceeding several hundred meters per minute, high speed misting becomes a serious challenge for maintaining a clean production environment. Centrifugal forces acting on the ink filaments as they snap cause the smallest fragments to be thrown into the air rather than returning to the rollers.
Dynamic Instability
Filament length and the speed of separation determine the quantity of fluid lost to the atmosphere. Reducing high speed misting involves adjusting the rheological properties of the ink to promote a shorter, cleaner break of the liquid bridge. High molecular weight polymers are sometimes added to increase the extensional viscosity and hold the filaments together until they retract.
If the ink is too short or lacks sufficient internal cohesion, the number of satellite droplets increases dramatically and leads to a dense fog around the printing units.
Operational Control
Temperature regulation of the ink train helps manage the fluid viscosity and reduces the tendency for droplet ejection. Efficient ventilation systems are also required to capture any high speed misting before it can impact operator health or contaminate the finished product.
