The benefits of contact and non-contact web cleaning for label production
The need to minimise wastage and achieve higher levels of productivity is a key priority for label converters, who often struggle to determine whether contact or non-contact cleaners are the best option for dealing with the removal of contamination from their web process. Ralph Simon, area sales manager for Meech Elektrostatik, the Belgian subsidiary of Meech International, talked to NarrowWebTech explaining the benefits of both cleaning processes for label printing applications.
Which cleaning processes are adopted traditionally?
Ralph Simon: Web cleaning systems need to achieve two main actions for successful cleaning. The boundary layer of air on the web must be broken, allowing contamination trapped under and within it to be removed, and the static charge on the web must be eliminated, to avoid contamination re-depositing on the web’s surface. Only a system this thorough will result in a spotless web, which is of paramount importance in label printing.
Narrow web presses used by label converters traditionally adopt tacky roller contact systems to efficiently remove contamination. This process provides excellent cleaning and is mainly used for filmic substrates. Tacky roller contact cleaning systems in particular use elastomer rollers to remove dry, unbonded contamination from a moving web, which is then transferred onto adhesive rolles where it is trapped. The design of the system also allows operators to see the contamination being collected on the adhesive roll.
However, there are some drawbacks to this process. While contact systems provide excellent cleaning, contamination will build up on the adhesive roll unless it is checked and changed on a regular basis. This results in a gradual deterioration until the adhesive is refreshed and performance returns to 100%. As a result, tacky roller contact web cleaning may not be the ideal choice for more heavily contaminated materials.
Which process do you advise for more heavily contaminated materials?
Ralph Simon: For substrates carrying higher contamination levels, contact vacuum systems or non-contact systems should be used. This is typical for paper or board. Non-contact or vacuum contact cleaning has the advantage that the contamination level does not affect the system performance and no consumables are required, which in turn reduces ongoing costs. A thorough non-contact web cleaning system is capable of removing contamination to below one micron and will deliver higher levels of cleanliness for label printing applications.
Where would a contact cleaning system best be installed and is this position any different for a non-contact cleaning system?
Ralph Simon: In order to ensure maximum web performance, cleaning systems should be installed as close to the critical application as possible. On a narrow web press, the typical solution is to install such a device before the first print station, with static control systems before each of the other print stations to make sure the web remains free of static charges. Such measures are most suitable to minimise the potential of static induced re-contamination.
Which challenges need to be overcome in web cleaning in the production of labels using new technologies, such as sensors or RFID based on printed electronics? And what solutions is Meech providing to overcome these challenges?
Ralph Simon: Non-contact web cleaners are the best systems to employ when dealing with these new, sensitive materials. Solar panels, for example, are made up of inkjet solar cells, which are manufactured by inkjet printers that lay down the semiconductor material and electrodes onto a solar cell substrate. For such a delicate substrate it is important that no contamination is attracted to the panel’s surface, but at the same time a contact system could prove to be too aggressive and leave marks or scratches on the web. Meech’s Cyclean non-contact web cleaner proves to be a good solution for such a challenge, as it can be used with all substrates, improving the flexibility of the press and is not affected by high contamination levels like a tacky roller system and has no consumable costs. The solution is capable of removing contamination to below one micron and incorporates fluid dynamic principles to deliver higher levels of cleanliness for a variety of web applications.
Editorial comment: This interview was first published in NarrowWebTech print issue, 4-2016, available as download in our shop, and is now published because this interview is still relevant for our readers.