Rotary bell atomization is a high energy process which creates an optimal spectrum of droplet sizes for paint application. Flowing from a central injector, the paint is dispersed from the center to the edges of a bell cup rotating at a high speed (usually from 25 to 70krpm). Centrifugal forces create paint ligaments that are cut into droplets in the air. The paint cloud is then shaped and transported by the shaping airflow, and generally enhanced inside an electrostatic field, providing an extremely high transfer efficiency.
The higher the paint viscosity, the higher the bell cup rotation needs to be to get the same droplet spectrum. The high voltage effect helps to decrease the droplet sizes resulting in a uniform film with a wet condition & a preferred metallic flake orientation rearranged with Vortex shaping air on the part coated.
How does it work?
An air driven turbine moves a bell cup at a high rotation speed proportionate to the air flow & pressure. The speed reading is made simply by the Sames noise frequency analysis (providing accuracy and reliability) or alternatively by a conventional optic signal record (sensitive to dirt & paint).
The bell cup, with its lightweight design, has been precisely balanced to reach this high rotating speed. Manufactured with the highest precision standards for the aeronautic & aerospace industries, the bell cup is constructed of aluminum or titanium.
As a result of designing our own SAMES KREMLIN turbines, we have complete control over the performance of the atomizers.
FINEST finishing for spray uniformity
The bell cup ensures uniformity of the droplet size spectrum leading to high finishing results.
Depending on its paint rheology, pattern size & the atomization level required, the proper bell cup must be chosen in the range of 35mm to 80mm diameter with concave or exponential shapes.
LONG LIFE bell cup
The 1st level of high speed bell cups are made of aluminum for a lightweight design & compatibility with most of paints. For an even longer bell cup life & for usage with specialty paints, Sames recommends titanium-made bell cups due to their high abrasion resistance. All bell cups have a distributor made in titanium.
In base coat and top coat, the metallic effect of the paint can be challenged with the electrostatic effect and the low particle speed bell technology. In the field, metallic flakes are getting oriented and lose their reflecting effect inside the film build with regular orientations. We have designed specific bell head systems with efficient air shroud effect and high rotating speed with wide bell cup diameter.
This principle gets very close to the gun application quality in term of color appearance but still get the benefits of the bell process with higher transfer efficiency and uniform surface.
Droplets size dispersion in number and volume. The average diameter D10 is around 29µm for the gun in these conditions.
Equivalent droplet dispersion with Bell
Droplets size dispersion in number and volume. The average diameter D10 is around 29µm for the bell in these conditions getting the same results as for the gun.
HIGH Flow Bell applications
Thanks to high rotation speed we can control the particle size and therefore get a good finishing quality at the highest paint flow required in production (up to 1000cc/min in some cases).