As a mechanical engineer with extensive experience in the design of flexographic printing presses, I can confidently say that the true heart of a good machine lies not only in its mechanical components, but in the invisible, high-speed flow of ink running through it. For years, optimizing this flow—whether in enclosed chamber systems, single-blade setups, or two-roller configurations—was a process guided by experience, intuition, and countless practical trials. Today, however, everything has changed thanks to Computational Fluid Dynamics (CFD).
What is CFD?
CFD is advanced simulation software that can accurately model the behavior of ink in various inking systems be it an enclosed chamber, an open system with a single doctor blade, or a two-roller setup. By inputting the physical properties of the ink (viscosity, density, surface tension) and the operating conditions (speed, mechanical forces), the software performs millions of calculations to generate dynamic maps of flow, pressure, and velocity. In essence, it provides an “X-ray view” of the ink’s movement, long before the machine is physically built.
This capability is essential, especially when dealing with high-speed applications where ink dynamics become complex and difficult to control.
Take rubber roller systems, for example: CFD helps prevent ink build-up at the roller contact points, which can otherwise lead to roller separation and uncontrolled ink leakage.
In open single-blade systems, CFD is key to preventing both ink starvation and splashing. If the ink tray doesn’t replenish the anilox surface quickly enough, it can cause under-inking and insufficient transfer. At the same time, splashing can impair print quality and efficiency. CFD allows engineers to precisely analyze how ink behaves inside the tray and how it moves onto the anilox. This makes it possible to optimize the tray’s shape and inlet positioning to ensure a consistent flow. Furthermore, it enables the study of turbulence caused by the doctor blade to determine the ideal blade angle and pressure, ensuring effective doctoring without ink misting and improving overall print quality.
Simulations also help identify the critical speed at which aquaplaning-like effects may occur. This insight allows for adjustments to rubber hardness, nip pressure, and side dam design to keep the ink film stable and prevent leakage.
Finally, whether the system is open or closed, CFD is essential for designing internal geometries that avoid ink starvation and air bubbles, ensuring even pressure along the doctor blade for perfect wiping performance and extended blade life.
The end result is a flexographic press capable of operating at much higher speeds without compromising on print quality.
Written by Dario C. | Team Giugni®
