A Vacuum Web Coater uses an industrial vacuum technology in order to create a sub-atmospheric pressurized environment, along with an atomic or molecular condensable vapor source that will deposit thin films and coatings onto the industrial materials. The vapor source can be derived from either a solid or liquid surface (such as physical vapor deposition, or PVD) or from a chemical vapor precursor (such as chemical vapor deposition, or CVD).
The process of vacuum web coating is as follows:
The industrial component or product will pass through a portion of the coater that is known as the application chamber. As it does, it will maintain a constant speed of up to five hundred feet per minute. As the industrial part enters the chamber, the part will pass through a template that has the exact same shape hole, or profile, as the shape of the industrial component or product that is passing through. As the industrial part exits the chamber, the part passes through yet another template, which is called the exit template. This exit template will also have a similar matching profile as the industrial component that is passing through this stage.
Paint is then drawn from a reservoir by a device called a diaphragm pump, which effectively filters for large particles, which is then delivered through a hole directly into the bottom of the coater head. Keep in mind that the fluid delivery diaphragm pump – as it should be – is low shear and should always be under low pressure. The level of the coating then rises within the head until the industrial part passing through is completely surrounded or immersed.
Once the above steps are complete, a vacuum will then be applied to the reservoir, as well as the application chamber. The reservoir is a sealed environment attached to the coating head. The coating head will contain the only available area for which air can pass through and rush in. This single area is the space that can be found between the industrial product and the template profile. Industrial organizations using a vacuum web coater should know that it is this ‘in-rush’ of air that is used to strip excess coating from the industrial product, and this removal of excess coating is what determines how much wet film thickness will be applied to the industrial part. The amount of excess coating removed will always find itself subject to the vacuum relief valve, the size of the templates, the linear speed of the industrial product, and the viscosity of the web coating. The vacuum web coating application and removal method stratifies the coating on removal, and is then subsequently drawn up and over a baffle, which will then drain to a reservoir.
For more information on web coating processes, reach out to the Jessup Manufacturing company.