Apply effective web cleaning technology to increase productivity and reduce downtime

[Chinese Packaging Network News] Packaging processing and printing companies are aware that high-production coil production lines require clean coils. By removing contaminants that are unavoidable due to the high-speed operation of the reels, an effective coil cleaning system can reduce line downtime and minimize the loss of low-quality products, thereby greatly increasing productivity.

From automotive products to solar panels, food, pharmaceuticals, and more, numerous packaging and printing applications can benefit from the technology of coil cleaning. But not just a solution can be applied to all these areas. Packaging processing and printing production lines deal with different materials, speed and tension are not the same, plus the type and degree of pollution is different, the way the cleaning is also different. Therefore, first of all, it is necessary to correctly understand the cause of the membrane contamination, why it occurs, and then find the correct solution.

The cause of coil contamination and its solution

There are two main reasons for the formation of dust, dirt, and various particle contamination on the coil. One is the interface layer produced by the coil running, and the other is the formation of electrostatic charge. An effective coil cleaning solution must be able to handle these two issues simultaneously.

The interface layer exists on the surface of all moving webs. It is formed by moving the coils to attract the surrounding air. This phenomenon occurs regardless of whether the speed of the coils is fast or slow. When the speed of the web is slow, the interface layer is relatively thin. As the speed of the web increases, the thickness of the interface layer also increases. It is important to break the interface layer because the contaminants will be directly adsorbed on the surface of the coil under the interfacial layer, and the contaminants will be absorbed in the interfacial layer. If the interface layer is not broken, contaminants on the surface of the web cannot be completely removed.

In addition, the surface of the coil is prone to static charges. The most typical cause of electrostatic charge is separation and friction. Static electricity is generated when a web is unwound (separated), and static electricity is generated when the web runs on a non-conductive roller (friction). Before being neutralized, the static charge absorbs the contaminants that have appeared on the surface of the coil. Moreover, electrostatic charges can also attract contaminants from the surrounding air to the surface of the coil, causing further contamination. Therefore, in order to achieve a perfect cleaning effect, the removal of electrostatic charge is a key technology of the coil surface cleaning solution.

It can be seen that in order to achieve an effective cleaning of the coil surface, three effective tasks must be successfully performed: first, break the interface layer; second, neutralize the electrostatic charge; and third, remove and trap contaminants on the surface of the coil.

Contact and contactless solutions

At present, there are two basic coil cleaning technologies that can effectively break the interface layer, ie contact and non-contact. This needs to be considered in consideration of various factors such as the material handled by the production line, use, flexibility, and budget.

Contact cleaning systems generally use two methods, vacuum technology or dust roll technology. Several types of contact vacuum technology are currently available on the market, such as the use of low-friction clean manifolds that come into contact with the web, breaking the interface layer, and detaching the contaminants from the surface of the web so that they can be vacuumed away. There is also a vacuum cleaning system with an adjustable brush that removes large dust particles from heavily contaminated surfaces. A contact system using a dust roller generally has a pair of elastic rollers that make full width contact with the web, breaking the interface layer and sticking away surface contaminants and preventing recontamination. Sticky rollers perform well when removing small particle contaminants (as small as 0.5 microns), but are not suitable for applications where severe contaminants need to be removed because the stick rollers themselves are quickly contaminated. In addition, the speed of the machine is also a limitation, generally cannot exceed 250 meters per minute.

Non-contact technology uses blow and vacuum to break the interface layer. Blowing and vacuum systems use air knives on both sides of the web to break the interface layer and remove contaminants. The vacuum airflow captures the turbulence and eliminates it. This type of system is usually both efficient and compact, and can be simply integrated into existing reel lines. The high-speed, non-contact roller rotates in the opposite direction 0.5 to 1 mm above the coil surface, creating its own high-speed high-speed interface layer, which destroys the interface layer on the surface of the coil. Even the smallest particles will be carried away from the web under this low-pressure, high-speed condition and collected in a vacuum chamber.

Control and eliminate static electricity

To ensure that the web is free from contamination, the cleaning system must also be equipped with an electrostatic control solution to eliminate static charges that can cause contamination on the surface of the web, especially when handling thin films. If it is not neutralized, the static electricity will adsorb the contaminants already existing on the surface of the material, and will also attract the pollutants in the surrounding air to the surface of the material, causing further pollution.

Static charges have both positive and negative potentials in polarity. Papers usually generate positive electrostatic charges, whereas thin films usually produce negative electrostatic charges. The effective means of controlling static electricity is to use ionization to neutralize static charges. In order to achieve a perfect cleaning effect, removing static electricity is a key part of clean technology.

At present, there are usually static elimination solutions based on AC and DC technologies. AC technology is through a special transformer, the conventional voltage is increased (usually boost can reach 7KV), such a high voltage is delivered to a group of high-voltage discharge needles, release the high-energy ion beam. A large number of positive and negative ions are continuously generated as the AC cycle changes, and the surface of the material with a positive or negative charge will quickly neutralize the electrostatic charge on the material surface when the ion wind arrives.

Pulsed DC voltage transformer technology is to change the conventional voltage into positive and negative electronic output. The specially designed tip discharge needle alternately emits positive and negative ion clouds, and the frequency and ion balance (emission ratio of positive and negative ions) can also be based on materials and different processes. The situation is adjusted to optimize electrostatic neutralization and elimination effects and to expand the scope of action.

Packaging Processing Printing and production involves many fields, and the different materials handled are also in a wide range, such as paper, labels, films, aluminum foil, coating, corrugated, wood, metal, and various composite and special materials. The installation and use of the coil cleaning system will help improve the efficiency of the packaging processing and printing production line and ensure that the products can be processed continuously and consistently with high quality.